Chev Venture

1999 Chev Venture Engine Overheating When driving When warm 

Car overheats within first 7 miles in morning from cold start. I took it for service and they replaced the thermostat. This appeared to fix the problem, but it reappeared the next day. Car has no heat from heater and the gage was pinned full temp. & overheat light was on. They have given up on fixing it.

I would check if the waterpump is actually flowing the coolant. The other issue is the vehicle probably had the "Dura-cool" coolant in it. You may want to do a search on the internet for "Dura-cool" and see what comes up, you may be interested. If you have no heat coming out you may have a plugged heater core as well. However if the vehicle is overheating, you may want to have the water pump checked

1997 Chev Venture Fuel System   

Venture was sitting at stop light and just shut off. Tried to restart and fired for a few seconds and died again. Towed home. Checked spark, good spark, checked timing via timing chain alignment marks, timing on. Changed the Camshaft sensor. Put a fuel pressure gauge on the fuel rail and seems to pressurize to 45PSI. Engine cranks hard and then will eventually fire and run rough for about 20-30 seconds and then when you step on the gas pedal to help it it dies. Starts right back up but then dies after about 20-30 seconds. Could the fuel pump still be an issue?

You can here the fuel pump start when the key is turned to the run position. We have also changed the fuel filter. We checked the voltages on the 7x crankshaft sensor and the 24x crankshaft hall effect sensor. Both checked within specs. Also the ignition coils were changed as well. Is there a second relay on the fuel pump that keep the fuel pump running while after the initial pressure is built up?

Hello, The fuel pressure regulator has to keep the pressure up or the engine will starve for fuel.

Monitor the fuel pressure while the engine runs the 20-30 seconds. Does it drop off? Will the fuel rail hold pressure after the key is turned on to pressurize the rail and then turned off for this test?

When the engine dies and doesn't start back up are the injectors firing?

There is no second relay for the fuel pump. The PCM controls the one relay as needed for prime and run.

Roger

The pressure does stay up when you crank the engine and will hold pressure right around 41-45psi. I have not checked it with the engine actually running. I will have to do that check tonight. Could the vacuum on the regulator possibly being plugged cause this problem. I did not check to see if it was but I will tonight just to make sure it is not. Going back to the pressure, It held 40psi overnight on the fule rail. Also after letting it crank for a few seconds when you release the key back to the run position you can here the fuel pump kick it and pressurize the system as if it was just being turned on. Is this normal?

It doesn't sound like you have a fuel pressure problem but I'm interested in the pressure reading when the engine runs.

By reasoning I'm thinking on full throttle acceleration that manifold vacuum drops way off. If vacuum to the fuel pressure regulator were restricted I would expect fuel pressure to increase to address a heavy engine load.

That release of the key from start to run causing the fuel pump to run again without having first turning the key off is wierd to me! Will releasing the key from start to just far enough toward run to allow the starter to drop out keep the engine running? (You would be physically holding the key part way between start and run)

That would point to an electrical ignition switch failing...

Roger

Good Point. I will have to try that. After work I will hook the pressure gauge back up and let you know what the pressure is while it is running if I can get it to start again. The last couple of times it did start so I am confident it will start again. I will also try to hold the key between the run and the start and see if it keeps running. Although it seemed to idle just when I would step on the gas it would just act like I was starving it from gas and shut off. Will post again after I run the tests. Thanks for the info.

Keith

I'll look for your post Sir. Thanks,

Roger

Well the pressure gauge reads 41psi with the key in the on position. While cranking it goes to about 42-43 when the van starts for the short 20sec or so it goes to 50 and stays solid until the van stalls. Also a new developement: There is now a very loud squeaking noise every time the engine turns over. I took off the accessory belt to rule out anything but the engine itself and it squeaks with the belt off as well. Checked inside the valve covers and the springs and lifters are dry. Could this be a result of a bad oil pump? Would the oil pump be causing all these problems? Is there a way to test it without dropping the subframe and removing the oil pan. Just want to make sure before I tear it all down and that is not a problem. The more the engine turns the louder the squeak.
Keith

Great! To accept my answer so that All Parts will pay me please close the question or click on the OK TO PAY MECHANIC button.

I thank you,

Roger

Great? What do you mean. I still have a van that I have no clue why it won't start. Do you think it is the oil pump?

What the?? My reply to you swapped with my reply to another. Freaky!!

What I said to you is that the computer does monitor oil pressure in order to keep firing the injectors. We do need to monitor the oil pressure. That squeel is a heavy concern.

Wal-Mart auto dept sells an after market oil pressure gauge for under $10. You'll want to tee it in with the current oil pressure sending unit (located near the oil filter) so the wire harness remains connected. You can find a tee at an auto parts store or larger hardware store.

Oil pressure could be the culprit here.

Roger

I was confused!! I will go check the local Wal Mart and put get a guage and try to rig up a tee. I don't recall seeing the sending unit by the filter but I will take your word on that. I can't find the sending unit anywhere in my Haynes manual. I hate the thought of the oil pump being bad but there is not much left to change. My wife tells me tonight that the oli light had come on several times a week before all this started. Is it safe to crank the engine with the loud noise. Today when it started the lifters were tapping as well like they had collapsed. I can probably get the gauge tonight but unfortunately the tee will have to wait until tomorrow, all parts stores are closed and so is the hardware.

I'm really worried. If the oil pump has chronic problems the squeel may be a seized bearing all ready. Depressing event. Wish I had known of the light warning low oil pressure sooner.

What size engine?

Roger

It is the 3.4. The famous engine that GM supplied with Dexcool that ate the intake manifold gasket. Already went through that routine. Should I proceed with the cheap gauge or go ahead and pull the pan?

I'm trying to figure out how to test the existing pump output without further risk to the moving parts.

I loved the old days when you could pop out the distributor and spin the pump with a blade in a screwdriver.

Getting oil to flow may relieve the squeeling sound but that is a scary gamble that wear can be assumed tolerable.

Believe I'd drop the pan and sift the oil for metal filings. And filet the oil filter to see what's inside...

Roger

Ok then. I have a job for tonight. I will lower the subframe and pull the pump out. Anything in particular I am looking for? When I pulled the pain to change the timing chain and oil pan gasket I thought about the oil pump as well but didn't change it. The oil in the bottom of the pan was a shiny metallic silver. I wondered if that was from the pump or the bearings. I will pull the pump out tonight.

The oil pump case may shows signs of scoring from the spinning gears.

Wouldn't it be a blessing if the pump were the source of the noise!!

When preparing a new oil pump for installation I pack the case and gears with Vasoline Petroleum Jelly to ensure it primes immediately. The jelly brings no harm to the lubrication system of the engine.

If you find shavings will a magnet attract them??

Roger

There were no shavings in the pan. Although there may be now. I will try to pick them up with a magnet. Is there a gear on the crankshaft that runs the oil pump. If so do I need to replace that as well or is it part of the oil pump?

The pic I looked at shows a long hex shaped vertical shaft drive. Wear on the shaft ends should be easy to spot. The oil pump bolts to the rear main bearing cap.

Roger

Well it shouldn't take but an hour or so to get to it so hopefully I will take it off see some wear and then replace and that will solve all the issues and the van will start and keep running. I like to think positive. I see the drive shaft comes seperate from the pump. Think it would be a good idea to change the shaft as well?

Given this engine's history I'd replace the shaft as "free labor" preventive maintenance.

Roger

We'll do. Dropping the oil pan twice is twice enough for me.

I wish you every advantage. Hope the van is a keeper...it will be worth your hard efforts.

Roger

Well I hope it is as well. Just bought it two years ago and the interior and exterior look immaculate. All the problems just started around Christmas time with that intake manifold gasket leaking.

Sounds like it is worth a lot and should be fixed.

Roger

I removed the oil pump. As I was taking it off the van a piece of rubber hit me in the face. Looks like some type of grommet or mangled seal of some sort. It was inside the oil pump. There was no oil at all in the oil pump. It was dry. The shaft shows worn spots about 2inches from each end. The sides are almost rounded in these areas. When I spin the pump it rattles like a bearing going out. Still no metal shavings in the pan. Clean oil. Not sure where the rubber piece came from. There is a vent tube on the valve cover that the grommet it sat in was missing when I did the intake gasket. Couldn't find it anywhere. I am thinking that this may be the piece I was looking for. Hard to see up in where the gear is that drives the pump. I will check it out good before I put the new one on.

Keith

I wouldn't have expected a piece like you describe could get past the pick-up tube screen for the oil pump.

Will you be taking a look at the main bearings and crank journals for wear?

Roger

I will look to see if there is any excessive wear. The rubber piece was in the tube that leads up into the engine itself. The screen was dirty but not plugged. What very little oil there was in the pump was black not the fresh oil I had jut put into it. I think the rubber whatever it was plugged the pump and that started the whole deal.

Does the engine turn over by hand with reasonable effort? I'm tempted to suggest removing all spark plugs to eliminate compression and see how much effort is needed to turn the engine.

And, it would be great while the plugs are out (and the pan back on) to spin the engine for 30 seconds with the starter to circulate oil before the first attempt to start it up.

Just thinking out loud,

Roger

Is this to avoid extra stress on the bearings that are needing oil? I can do that. Turn the crank can be done with a 3/8 inch ratchet that is about 8 inches long with one hand. Not too difficult. Parts store has to order the oil pump so I won't get one tonight.

Yes I was suggesting to get oil to the moving parts before the load of the engine starting up.

That's all I had in mind.

Roger

That is a good thought. I was thinking a way to get the oil in there as well. Guess it makes sense to use the oil pump and have it push the oil up through there. Will I be able to turn it fast enough for the oil pressure to move the oil though?

Not by hand...using the starter motor.

Ok. I will pull the plugs and turn it over with the starter. I will get all the parts tomorrow. I ordered the pump, screen, shaft and the nylon guide for the shaft. I believe that is all I need.

I'll look for you post later in the week.

Roger

Well got the new oil pump and put it in. Cranked the engine a few times like you said to move the oil. Then tried to start it. Seemed to when it first cranked it fired right away and then cranked hard. Then it cranked and started and ran for about 30 sec again and seemed that the longer it ran the more it was tightening up and stalled again. Then the starter went out for the second time. The squeaking is still there but not nearly as loud as it was. Barely noticeable now. Seems to have more power when it does fire now. Is this going to be hard to start with all the lifters starved for oil? Should I expect this or should it take right off? I will have to go exchange the starter later today. Any more ideas that may fix this thing?

I would expect the engine to stumble or run rough while lifters pump up. The news of tightening up as it runs is disturbing. When it stalls how hard is it to turn by hand? Lord I hope it doesn't spin a bearing.

How did the crank journals look?

When it acts like it will stall does it try to respond to throttle?

Without hands on I'm pressed for ideas....

Roger

Didn't see much wear on the crank journals. Although there was one place where there was a lot of new metal grindings. Looked like someone was sanding something inside the engine. Couldn't tell where it originated from. The engine is still about the same to turn by hand after it has stalled. Acutally turns over fairly easily after it sits for a couple of minutes.

When it starts to stall I step on the gas and it acts like I am starving it for fuel. Although when it first started I did push down on the pedal and the idle increased until it started tightening up.

I have hands on and I still can't figure this one out. Fuel pressure still stays around 45psi when cranking and about 50 when it actually starts. Never drops off. Hold pressure over night. This time when it started it was like it was only fireing on two or three cylinders.

Maybe it will smooth out. Do you suspect injector problems?

Roger

Well I had to change the starter for the second time. The spline that holds the gear that engages the flywheel was stripped. This is the second starter that has done this. Yet you can turn the flywheel with your hand so I don't think it is seized up. Engine now cranks but seems to be fireing before tdc. Thought plug wires were crossed but double checked and wiring is ok. Never had problems with the injectors in the past but could be a possiblity. We were wondering if it could be the oil pressure sending unit. Could this have been messed up with the low oil pressure problem or does it need reset? We are going to get at it again in the morning. I will probably replace the oil pressure sending unit unless you know a way to bypass the sending unit.

I don't know of a way to bypass the oil pressure sending unit. I've not heard of a reset feature either.

Is the flywheel ring gear okay? Do the replacement starters have a NO SHIM stamp? Are shims used?

Roger

Starters were rebuilt units. No Shim stamps. Not using shims. Now have a brand new starter that is GM inspected. Cost a lot more but right now I need the quality. Well I will probably try replacing the sending unit then in the morning and go from there.
Thanks again. This seems like a never ending problem.

I'll be conducting a car care clinic until 2:00 p.m. CDT tomorrow. I'll check in after...

Roger

Sounds good. I will post any findings I encounter tomorrow.

What a day, I'm finally home again.

Any news?

Roger

Well I hope your day was better than mine. We tried it this morning and same thing. I disconnect the ignition module and the fuel pump and turn it over and it sounds like there is nothing wrong with it. I reconnect the ignition and fuel and it fires sporatically and rocks the engine back and forth. Still seems like a timing issue. So today we change both crankshaft position sensors, and the ignition control module per the advice of a local chevy mechanic. Same thing although it sounds smoother when it fires but still sounds like it is fire before top dead center. Now the back crankshaft sensor had a wire on it that looked a little burnt. So we got a different wire but it looks to be longer and a thicker gauge wire. Could that make enough resistance to make a difference. Before we were getting about 250mv AC. Now we are getting almost 800mv AC. I just don't know where to go from here. Also we noticed the oil light is still not going out when it cranks. We changed the oil sending unit sensor as well. Any words of wisdom? I am ready to tow this thing to the junk yard. It is probably something so simple that we are overlooking it. I forgot to mention that we changed all the plugs and wires today as well. Help!!!

You've tried everything that comes to mind!

Are the fuel injectors firing prooperly? Could the PCM have a poor ground? Does the PCM come out easily? I wonder if it has any odd smell from the circuit board...?

The wire you replaced on the rear crankshaft sensor is larger in gauge as well as somewhat longer. It would have less resistance than the previous wire as the larger gauge wire will handle more current. It would have to be a lot longer before resistance would go up.

I don't have the schematic in front of me. Does this engine have a mass airflow sensor (MAF)? If so what happens if while cranking you tap gently on the sensor?

Will disconnecting the manifold absolute pressure sensor (MAP) electrically have an affect?

Roger

It does have a MAF and a MAP sensor. The injectors are connected to the MAP sensor so it is possible the MAP sensor could have a problem. I will try tapping on the MAF and also I will disconnect the MAP sensor and see it it makes a difference. I will pull the PCM and see if I can find any broken wires or a bad ground. Do you know if the PCM can be checked by a GM dealer. No parts place can check it. I am about to go to the junk yard and pick one up to see if it is the PCM. All the sensors are giving correct voltages it just is not timing everything together. Acts like it wants to turn the engine the wrong way when it does fire.

No GM Dealer can test the PCM. I retired from a Cadillac dealership service dept. If we could have tested a PCM locally I truely believe that the warranty claims would have been reduced.

Fingers crossed here...so are my eyes.

Roger

Well I noticed when I was trying to start it that every trouble light inside the van goes out when it is cranking even the service engine light. Except the oil pressure light and the battery light. Shouldn't the oil pressure light go out once the engine is cranking? I am going to hook up a pressure gauge to the sending unit and see if it is pumping oil at all. I will let you know what I find.

Ok get this. No oil pressure. Hooked vacuum to line and cannot pull any oil through where the sending unit is. Trying a stronger vacuum. Sending unit was completely dry. No oil at all. What could this mean?

Did you open the case of the new oil pump and pack the gears and case with Vaseline before installation? Has the oil pressure light gone out since reassembly at all?

Roger

I did not open the case. My father n law said to just prime it by pouring oil in the screen and turning the drive shaft until it pulled oil thourgh by itself. I really wish at this point I wouldn't have listened to him and let him prime it for me. I told him about the vaseline but he thought this would work. The oil light seemed to go off when we first put the pump on but since the first time it fired after the pump was put on it has not gone out. We tested the sending unit by blowing air into it and the light does go off when pressure is applied. We also hooked up a small tube to see if we could draw oil up through the pump and could not do it that way either. Would this cause the van to not fire up at all or would it start and then cut out? Is there any way to prime that pump without pulling it off the van again?

We've both changed oil in a vehicle before. And in the first few seconds after restarting the engine the light stays on for a second or the gauge needle doesn't move for a short pause.

I would expect a start and stall scenerio instead of a no start at all to be the norm.

In very rare cases when an oil pump won't prime I have disabled the ignition coils, removed the spark plugs so cranking speed will increase and put too much oil in the engine crankcase. I'd crank it until it primed while ensuring not to overheat the starter.

I've even raised the front end with a twin post lift or a wrecker to submerge the oil pump as well as the pick up screen.

That vaseline pack suggestion is the best advice I could have given you for ensuring the oil pump would prime.

Once the pump primed I'd have to drain the excess oil back out, put things back in order and start the engine.

Roger

I will overfill the oil then and give that method a shot. Sure beats taking the frame and pan off again. Maybe I will get lucky for once with this thing. It might be a blocked passage way from the oil pump as well. I thought it looked clear before I put it back on but there might have been something up higher that I didn't see. I will try the priming method and see what happens then pull the pump.

Thanks again.

Should you want to release the question for others to try and answer I will not take offense. I may have missed something that another provider just might shine the light on the problem after reading our dialog.

I remain committed to trying to help in any way I can.

Roger

Thanks for all the input. You have been a wealth of information. I may just do that to see if anyone else has any ideas. Thank so much!!

Please tell us where the number 1, 2, and 3 cylinders are on your engine-- so we know you have them correct.

Have you checked cylinder compression?

If you still have the old sending unit, you could plug it in and pressurize it (confirming or eliminating any concerns here).

Number one is on the passenger side of the engine in next to the fire wall, #2 is same side by the radiator and number three is in the middle by the firewall.

We have checked both sending units and the old one no longer gives a signal. The new one when pressurized makes the light go out.

Compression was in specs with the Haynes Service manual.

Now try spraying some carburetor cleaner into a vacuum hose and see if the engine will run on this.

Does it matter which vacuum hose? We tried ether through the air intake duct and it seemed to fire spiratically just like it does without it. When we pulled the plugs the number 4 cylinder was flooded, the others looked like they barely had any fuel on them at all. We listened to the injectors and they are all ticking like they are functioning.

Unplug the injector to the number 4 cylinder (after clearing it), attempt to start again and see if this cylinder floods again. Is this cylinder "flooded" or "full of gas flooded", if the latter stop before trying anything. The injector must be stuck open, unless fuel is coming from another source (in the event the vacuum hose for the fuel pressure regulator is near this cylinder).

It is flooded with gas. The vacuum hose for the regulator is next to cylinder 6 at the return side of the fuel rail. I will try unplugging that injector and go from there. Still have to get that oil pump reprimed.

Ok well I removed all the spark plugs to find that all were carbon covered except number 4 cylinder. It looked brand new except for a little carbonation where it should be at the top. All the others were black with carbon all the way down to the threads. Still can't get the oil pumpe primed so I will have to drop the subframe and oil pan and reprime the pump.

Here is the latest, I took the oil pump off and filled it with oil and then packed it with vaseline. Then I put it back on the vehicle and put oil in the pan. With the plugs out and ignition and fuel disable I turned it over to get the oil flowing. Still no oil pressure. I removed the sending unit and the light goes out when it is pressurized. I put it all back together to see if maybe it would start and I could get the rpm's up and the oil would start pumping. Well it did start and ran for about 30 seconds. I was able to step on the gas and get the engine to accelerate. The engine was probably at 2000rpm or more. Squeaked like it had no oil and then shut off. Can't say it ran badly it just squeaked like crazy and then acted like the fuel was shut off. This is the second time I have tried to prime this oil pump. What can I do to get the oil pressure going?

Considering that you found chunks of rubber in the origional pump, have you tried blowing compressed air through the oil system? You could start at the oil pressure sender,Does the oil pressure senser also have a circuit that shuts the fuel pump off if no oil pressure?

When I had the pump off the van I did blow air up through the oil inlet and oil (what very little there was)sprayed out of the oil sending unit hole and other passageways. The PCM does shut off the fuel pump if the sending unit is reporting that there is no oil pressure.

Still sounds like a partial plugged oil gallery, which would be tough to find and clean out.Perhaps a little pressurized solvent introdused in the oil pressure port, might backflush it?
Might it be poss to bypass the oil pressure switch for more than a few seconds running time to build up oil pressure?

Well I took the pump off again last night and noticed that the pump did not spin at all. My vaseline pack job was still completely like it was when I put it on. So we dropped the pump and checked to see if the drive shaft was turning when the engine cranked. It was not. So I am pretty sure that the oil pump drive gear is messed up. Possibly the sheer pin has given way when the silicone fell into the old oil pump. So
I will be dismantling the intake to get down to the cover for that gear and will pull it out and see what the problem is. Hopefully it will be just the gear and not the camshaft.

I have seen (and experienced) broken oil pump driveshafts also.It would take a lot to damage a gear, but if timing chain or belt has a problem and the cam is not turning....

Well I got the oil pump drive out and found the gear on the cam was not turning. I have a two piece camshaft. Broke right in half. I got the camshaft out. One of the bearings was completely destroyed and fell out of the camshaft hole. I have a pushrod that is severely bent as well. Now I just have to fing the removal tool for the bearings and order the new camshaft and bearings and get some lube for them.

That would certainly explain the non turning cam gear!
The cam gear removal/install tool is avail rental if you look hard enough.Kinda expensive to buy.
Good luck!

Tell me about it. Tool costs more than the camshaft at a lot of places. Someone told me the local Autozone has one they loan out so I will talk to them. I have all the parts ordered that I need so now I just have to wait for everything to get in.

yup, Its a special tool that has different sized mandrels.The cam beraings are numbered and different sizes, biggest at rear.Back one goes in first,etc.Ensure that the oil hole lines up too!

Well I finally received all the parts I needed to put the engine back together on Saturday. So we did a valve job, hone the piston cylinders, changed all the bearings on both shafts replaced the rod that had the bad bearing and put it all back together. I am now driving it. It sounds and feels better now than it did when we test drove it at the car dealer. Will take it easy for a few days and then gradually get on it. Sounds great, runs great. Thanks for all the help.