2000 Olds Mini Van Overheating

[LateApexer]

Hello everyone - this is my first post on the forum, thank you in advance for your collective knowledge and insight.

I have a 2000 Olds Minivan that is overheating. The shop has replaced the thermostat which seemed to be the cure initially. Now 4 weeks later, it's overheating again.

When I am in motion, the temp goes back down. In stop and go traffic, it heats up to the red.

My new mechanic thinks the water pump is going and the head gasket was probably burnt when it overheated 4 weeks ago.

If air passing through the radiator (while driving "fast") cools the engine, it means water is circulating, correct? Would that indicate the water pump is working right?

Any ideas what is causing it to overheat?

I did a quick search and am not sure what the answer was. I am happy to try to trouble shoot or answer any questions I did not cover in the post.

Again, many thanks for any help.

 

[Drew99GT]

Are the radiator fans turning on? What engine? Many older GMs have fairly severe cooling system problems. Is it losing coolant?

 

[sciphi]

3400 V6. If it has had Dex-Cool, it's likely Dex-sludged the radiator. Probably replacing the radiator will help.

IIRC, 3400 head gasket problems are rare. Intake manifold gaskets they eat like candy.

 

[The_Eric]

Lets start by turning on the A/C. When you do that, the cooling fan(s) should come on. This will let you know if the fan motor or it's wiring is bad. If it passes the first test, move to the second. If not, check the fan, relay and wiring.

Second Test: Let the engine warm up. Somewhere around 220-230*, the fan should kick on. If not, it could be a relay (likely) or a sensor.

It's less likely that the water pump is going south, because if that were the case, it would get hot under more conditions. It is entirely possible your new mech is right, but check these things out first. I think you'd kick yourself if it was something as cheap and easy as a relay and you had the mech replace the head gaskets and water pump.

 

[LateApexer]

The fans only come on when the temp gauge hits the red.

I'll have to double check which engine it has. I was not aware there were optional engines. It's actually my parent's car.

It was low on antifreeze. All the new mechanic did was top it up and he thought it helped. He thinks it will need a new water pump soon. I have not seen any smoke (white or otherwise) out the tail pipe.

 

[LateApexer]

Thanks for your feedback.

I THINK the fans come on when the AC is turned on. I'll have to double check. I only checked before with the AC off (and the fans only came on when very hot on the gauge) Will confirm to the board tomorrow.

Thanks again for the ideas.

 

[crazyoildude]

check to see the fans are working if they are not turn the a/c on max and see if they work then.. If so its the sensor

 

[Brons2]

Low on coolant? DANGER WILL ROBINSON!

Your lower intake manifold probably needs to be replaced.

 

[oilmaven]

Yep...sounds like the intake manifold gaskets have bit the dust. Although it'll cost a few bucks for the labor, I'd replace both the upper and lower gaskets with Fel Pro gaskets (the "improved" GM designs can still fail down the road). The good news is once they're replaced (followed by a thorough flush of the cooling system), the engine will probably run forever. If you delay the repair you run the risk of damaging the engine.

 

[LateApexer]

I just tested the AC, and the fans did NOT come on. They DO come on when the temp gauge hits the red. Does that indicate a relay or sensor should be changed?

How do we diagnose the manifold gaskets?

Do I monitor the coolent level? I have not seen any smoke and the engine remains cool when driven in highway conditions (40+ MPH consistent airflow)

 

[IndyIan]

Your cooling fan should come on when the needle goes just over "half". 212F in my Neon and it stays on until temps drop to 204F, in the red is something like 230F or more... Something is messed up that controls the fans, relay or sensor, as the temp should never budge over half driving in traffic.

 

[Trav]

Quote:
(the "improved" GM designs can still fail down the road).


What makes the Fel Pro better?
Since the newest soft aluminum frame GM gaskets have only been in production for about a year and a half it's a little early to make that statement isn't it?
As a matter of fact Fel Pro uses the GM aluminum frame design for their high end 3800 Gen II LIM gasket.

OP I go along with the LIM gasket problem and also possibly a sludged radiator. Both are very common on these 3.4 engines. AFAIK there was no 3800 offered in 2000 in these vans. The 3.4 replaced the 3.1 with a 3.8 option.
I have done a few head gaskets on these when the engine had overheated a few times and the heads warped.

Doing the LIM gaskets is normally not a problem until you put the engine in this van body, it is a semi difficult PITA.The head gaskets are a bloody nightmare even after doing a few of them. The labor to do the head gasket and possibly heads maybe more than you want to put into a vehicle this age.

It is very rare to see a water pump fail this way on these.

 

[onion]

Has GM come out with a metal-framed LIM gasket for the 3100/3400 engines? Last I knew, their 'improved' gasket included some metal spacers to prevent over-tightening, but it was still a plastic-framed gasket. And while this was an improvement, they still failed in much the same way as the old style gaskets. Has this changed?

Fel-Pro came out with the metal-framed lower intake manifold gaskets around 2005-2006. At the time, they were better than anything available from GM.

 

[Trav]

I have been using Fel Pro permadry on the 3.4 and GM aluminum frame on the 3800.The GM parts guy at the local dealer offered metal core gaskets for the 3.4 but i haven't used them.
Only the Permadry is metal the cheaper Fel Pro is second rev with metal spacers IIRC.

You are right about the second revision using metal spacers and was just as bad as the original but AFAIK GM had a new revision of all their problematic V6 gaskets early last year.

 

[LateApexer]

How do I tell if it's the intake manifold gaskets?

Also, if it cools down when driving, wouldn't that indicate the radiator is not slugged up?

 

[onion]

If the lower intake gaskets are leaking, you will generally see coolant in the oil and/or external leakage.

Lots of people replace head gaskets when the see coolant in the oil in these engines. But 90+% of the time, it's just the lower intake gaskets that are leaking.

If the LIM gaskets have never been replaced, then there's a very good chance that that's your problem. They ALL fail in the 3400 and 3100 engines... it's a matter of 'when', not 'if'.

Quote:
Also, if it cools down when driving, wouldn't that indicate the radiator is not slugged up?


That doesn't necessarily tell you a whole lot.

Your best bet is to confirm whether or not the vehicle is low on or losing coolant. If so, find out why (probably intake gaskets). And inspect the cooling system upon teardown.

And if the vehicle has been driven for an extended time with low coolant... odds are that it's sludged.

 

[mechtech2]

Are you losing coolant?
This would show if the manifold and /or head gasket are compromised.
Water pumps with bad impellers are TOUGH to diagnose, but they do go bad. The drive belt may be slipping, as well.
Bad radiator? Sure could be! Plugged to some degree is my guess.

 

[crazyoildude]

its not the intake manifold gaskets if it was it would get hot when driving and the fans should go on at about 3/4 or so the guages are just guides they are not exact

 

[crazyoildude]

if it stays cool at 50 mph and gets hot when you stop for a while or when you are in traffic its the fan!
if you dont fix it soon it will then be gaskets and heads and transmission etc
If you want jump thje relay and have the fan going all day while driving if it dont overheat then again its the fan!
Everyone is quick to say its the intake gaskets when in fact most of them are ok believe me we see engines all day long and those gm engines are pretty strong