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Chevy Venture Engine Problems



  • i have a 2000 venture that needs a new thermostat. Wheres is it and is it hard to change?
  • russ23russ23 Posts: 25
    Thermostat is under the throttle body assy (driver side facing the engine). Look for the radiator hose follow it to the block. It is contained in a aluminum housing. To get to it remove air cleaner hose. Book says you should be able to get to it that way, but I doubt it. May have to remove the upper intake manifold. If you want to change thermostat because of an overheating problem, that may not fix it.. Main cause of overheating on this engine is leaking cylinder head and/or intake manifold gaskets. If cylinder head gasket, it is probably cheaper to get another engine from junkyard, that is what I did. To test use a block checker (bulb with colored fluid). Insert in radiator cap opening, with engine running sample air in radiator. If fluid changes color you have a cylinder head gasket leak into the coolant which causes overheating. If no change in color, go for both upper and lower intake manifold gaskets.
  • If I am not mistaken, the thermostat will only fit in one way.
  • russ23russ23 Posts: 25
    Not sure if you can install the thermostat incorrectly. I presume the basis of the question is that you installed it and not sure you did it correctly!!! If so you might be able to remove the radiator hose and maybe look inside. Better not see the thermostat spring!! If engine is still overheating, I would recommend pulling the thermostat entirely and running engine without it. If it overheats then the above problems are the cause.

    Thermostat must always be installed so the spring/capsule is inside the engine.

    MURPHY's LAW is usually in operation and if it can be done wrong it is highly likely you will do it the wrong way!

    It is best to remember how the thermostat works rather than depending on how it looks to install it correctly. Thermostats are always mounted in the water OUTLET end of the engine that moves water to the top of the radiator. The water pump is the INLET/SUCTION side and it draws water from the radiator bottom (cooler water because heat rises). Purpose of thermostat is to restrict water flow in the engine until the engine heats up. When water temp gets hot enough the heat capsule weakens up and allows the spring to open the thermostat valve. IF THE CAPSULE/SPRING IS NOT ON THE ENGINE SIDE THE CAPSULE CANNOT BE HEATED. By the way I have been there and installed the thermostat wrong because I was looking at how it looks rather than how it should work.
  • Hi
    I have a 98 chevy venture. my problem is overheating. I change the thermostat,thermostat sensor & waterpump but she still overheats. I've read everybody commets and answers but i haven't read about the fans.
    My fans don't turn on when the car is hot. I turn on the ac and then it turns on.
    But thay turn off after a while and then she starts to over heat again. only when
    she gets real hot the fans may kick in. Dose anybody out there ever notice this
    and is there a solution for this fix. Can someone help.
    I love my car and i don't want to get rid of her.
    Thanks to all of you.
  • russ23russ23 Posts: 25
    I wished I could make easy for you but it isn't. No silver bullets here. I have a complete set of factory service manuals for my 1998 Venture and troubleshooting this problem is over a dozen pages. You might have to bite the bullet and go to the dealer and at least pay for the diagnosis rather than wasting more money throwing parts at it. The fans are controlled by the engine computer based on input from the engine coolant temp sensor (and probably other sensors as well). All those can cause the problem to include wiring. You did not mention messing with the coolant relays? These are the usual problem.

    Note: fan position is from drivers seat, so it is reversed when looking at them from the front of the van.

    Under the hood over the battery is a fuse box. Fuse #6 (30amp) powers the right/low speed fan you say does not come on (w/o A/c). Check to make sure it is okay. Also check fuse #1, which controls the other left/high speed fan (in case I get this mixed up). Presuming they are both ok relays #9,10 and 12 (gray color?) control both fans. They are all the same but #12 (by itself) controls the right/low speed fan. I am guessing it might be the culprit. Pull #9 and install it into #12 (leave #9 out). Nothing will happen until the engine overheats, so go for a short ride. If the fan then comes on the relay you pulled is the problem. If it still does not come on, (with engine running) pull the relay and use a digital voltmeter on 20 volts dc scale and test cavity #30 (one probe there and one to ground) for power. If you get power that relay is also bad, if no power you might want to call a priest because it gets real tough now. The problem is in the engine computer or another sensor/wiring or what the hell. It could be anything. Good Luck. Don't you just love cars!!!!
  • russ23russ23 Posts: 25
    This is let everyone know that you can pull the engine out the top and do not have to drop it from the bottom. I have pulled my 1998 three times out the top so I know what I am talking about. Too long to tell you but if you email me at, I will be glad to send you might experience. It is pretty straight forward. Key is to just rope up the hood to protect the windshield (do not remore). Remove the windshield wiper assembly as one piece with the arms (6 screws under the plastic apron). Then remove all the junk like cruise control, battery, upper intake manifold, all exhaust manifolds, etc. You will then see there is plenty of room to pull out. I used a cheap cherry picker. The key is to use a chain stretched tight against the block so you have room to lift with the nose of the cherry picker. Anyway, it is not magic. I have pulled a half dozen different chevy engines and this is the easiest. Astro van is the hardest.
  • I had the Intake gasket replaced about 6 months ago. Yesterday i had the water pump,and the Thermostat changed. but still getting high back pressure at the Radiator cap,and a jumpy Temp Gauge.
  • russ23russ23 Posts: 25
    Sounds to me the cylinder head gaskets are gone and allowing combustion gas to heat the coolant. Remotely a clogged radiator. To be sure you need to perform a block test. Sold at most parts houses and definitely NAPA it is turkey baster type tester you stick into the radiator cap opening and watch change of color in test liquid. If it changes from blue to yellow you have blown cylinder head gasket. If you have high miles, I would recommend used engine instead since heads can be warped from heat and bearings could be worn out or getting ready to go.
  • I have a insurance adjuster company we have 6 chevy ventures bought new or with low milage. They are awful each week I am spending 200 to 300 dollars to keep them running. I have overhauled the entire cooling system. Nothing works, Chevrolet should be ashame selling such bogus version of a van. If you have one sell it quick before something else go wrong
  • jeanzjeanz Posts: 1
    Haven't had this issue with Venture but other GM vehicles would overheat then cool down with heater full blast. With these vehicles a thorough radiator flush completely solved the issue, also with these vehicles the flush was an annual event, at 13 months all would over heat again.
  • Just out of curiosity, if you let the engine cool down to the point where you can remove the radiator cap, shouldn't you see fluid moving from the upper radiator hose (furthest from cap on top of the radiator) through the cooling fins back tot he lower hose once the thermostat opens?

    I don't see any fluids moving on mine, my thought is water pump and/or thermostat. The top radiator hose gets warm but not hot, and the lower hose is ice cold. Only takes about 2-3 minutes for the engine to go from zero to 50%, then another minute to get to 75% of the gauge.

  • First,

    IMO, there is no issue with Dexcool and sludge. the "sludge" is an supplement/additative GM added to the coolant as "insurance". it's basically ground walnut shells, and ginger root. Cast aluminum is pourus, and this can seal up any micro leaks. this will easily pass thru any coolant system, and when it does, it'l be ground up by the water pump. when exposed to air, the mixture turns to a jelly like rubber sealant.

    Second, I would suggest anyone that suffers from the cold coolant in the overflow, or temperature fluctuations, cold heet in cabin to have their thermostat changed, but have a 1/8 hole drilled into the outer portion of the t-stat. (between the thermo mechanism, and where the rubber gasket is. seems the 3.4 does indeed suffer from HG issues, but it is made worse by the fact that when the thermostat is closed (on a cold engine), or a running engine that's moving down a cold highway where the thermostat closes for some time. what happens is that tiny amount of air bubbles (less than a cup full) float up to the thermostats thermo sensor, and prevent the thermostat from properly detecting the temp of the coolant!. it varies, because if you make a turn, are on a bouncy road etc, the coolant will splash up & sometimes open the stat enough for you not to overheet, but you will see it on yor gauge as fluctuations. by drilling a hole, your 3.4 will indeed maintain it's 195 degrees, BUT any air trapped under the stat will be forced up to the highest point in the coolant system (luckily the cap), and as the pressure increases, it will be slowly expelled without damage to the overflow tank. Sometimes, small amounts of coolant will be dripped into the tank as well (even happens with a healthy engine), but during normal driving with acceleration, some of you know that the cooling system has a vaccume where it sucks in. - seen by a radiator hose collapsing a little or getting soft on a hot engine. - the good news is that the hose in the overflow tank is submerged in coolant, and it will suck that in, and not the air. as the pressure in the cooling system gets to operating temps, and 15psi, the amount of exhaust gases squeezed into the system diminishes. DO NOT USE HG IN A BOTTLE. you fill screw up the entire cooling system.

    BTW, many cars have self purging systems that resolve this issue unfortunately not the 3.4 we must make it ourslves.

  • Hi, I've recently had the intake gaskets replaced, 200,000 kms/162,000 miles. I was smelling the coolant in the cab and could see some leaking on the engine. Works great, like new except there is a reduction of fuel mileage from 33-34mpg to 29-30. Mechanic does not have any ideas.
    Anyone out there encounter same?
  • neustkgneustkg Posts: 35
    Wow! How were you getting 33-34mpg? At best on the highway we got something like 30-31mpg but that was when we were keeping the speed between 65-70mph. We drive across Wyoming and Idaho once a year and since the speed limit is 75, we keep it between 75-79 and get an average of about 27-28mpg (which makes sense due to the higher speeds) depending on the wind. You pretty much have to drive at least 75 or you get ran over by semis (hypermilers would be in danger on these highways).
  • I have to clarify that I was doing 60 mph most of the time, on repeated long trips and this is in Imperial gallons, which are larger than U.S. Gals., also using nothing but Shell gasoline. Alas I can't seem to recover my former fuel mileage.
  • I might of found a very effective way of ilemminating the air pockets in the cooling system with out opening the bleed off valves all the time. My daughter has a 2002 Venture and has been having problems with over heating and no heat for defrosters or interior of the van. A mechanic changed the thermostat, but problem remand. Everytime we bleed the cooling system, it would go away for short periods and we had heat in the van. I had an idea, thinking of the old cast iron radiators in homes with the pressure relief valves, these are closed loop pressurized systems, and they had automatic bleeders to remove any air pockets, so why wouldn't this work on the van. Well, I found one thru a McMaster catalog for $26.78, Installed it and right away it started working as thew van should of. The valve is made by Maid-0-Mist and is called Auto-Vent No.78. All you have to do is remove the total bleeder assembly on the passenger side of the motor, and screw the automatic bleeder valve with the 1/8" NPT valve body directly into the bleeder port. Done, about three minutes and no more overheating problems and instant heat/defrosters in the van again. Doing research, it looks like you can order these automatic air eliminators right from your friendly Ace Hardware stores for a cost of $10.00 to $15.00 dollars.
  • Does anyone know the true answer to this problem???
  • WOW KellerMeier - that's great you got this going. I am curious how this works out in the long run. I just did a Head gasket job on my Venture, and the gasket was intact, but the head had a small warp that the machine shop milled out. I'm sure your solution will work for many 3.4's that have a very minor amount of air entering the coolant - that reaks havic on the ability of the water pump to move the coolant thru the block. aside from the 1/16 drill hole in the stat, I also thought of using a 180 degree stat to keep the block 15 degrees cooler, and thus reduce the amount of expansion on the aluminum heads. Unfortunately because of emissions standards, it will be hard to find anyone who will match up a 180 to a 195 & sell it to you.
  • russ23russ23 Posts: 25
    What problem?
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