Mechanics

CAR RUNNING TEMP VARIES WILDLY.

1998 Chevrolet Lumina • 12,100 miles

In the last year - we figured our 98 Lumina had fallen victim to the dread faulty LIM Gasket issue that a lot of the GM 3.1 V6's have had.

We had the dreaded mud coolant, random lose of coolant and overheating. I got in there, changed ECT before realizing this, installed new gaskets and new thermostat - things were much better for most of the summer, and the temp was solid whenever it got to running temp. Sometimes running temp was a little higher, but no overheating. I had used primarily water until we knew this problem was fixed. We knew this was just part of the problem, as we were also not getting the fan relays to switch on during traffic. For the summer, I just used the A/C On to override, and run the fans constantly (we were getting a low coolant warning, just need to replace sensor, and all that might clear up.)

One of the issues we're experiencing NOW is, regardless of speed, stopped or going - there are random temp variations going all the way to 3/4 the gauge. Stays steady, and then will randomly come down. Coolant is evaporating in the overflow, but not in the radiator itself, it appears. Checked multiple times, during 1-2 week intervals - to only needing less than a cup to top off.

Checked a number of things:
Water pressure seems too light in return hose. When bleeder valve is opened @return, it spurts but not in steady stream, water intake bleed @ transfer case is nothing until fans turn off - water temperature stays constant, but it'll start spitting as if boiling, again not in steady streams, and then reverses if coolant fans are reactivated, until nothing is coming out again.


I'm at a loss. I'm about to just pull off the water pump and replace it - but what else could cause this? Much less fans not switching on, with 3 good relays. The low coolant light couldn't be triggering the PCM for that could it?



Avatar
W_nter
September 14, 2011.




First of all, you said you had a rust issue. Did you remove the rad and have it flow tested? Did you have a leak down test to verify the head gaskets? You have covered all the other basics. I think removing the water pump and checking the impeller is a good idea.

Roy

ASEMaster6371
Sep 14, 2011.
No, not yet on the radiator. This is a new issue that has creeped up since the 1st. And also, unfortunately no - did not perform the leak down, as money was tight - every indication I was receiving from my research pointed to a faulty LIM gasket - and it was absolutely blown.

The way it's behaving now - an I mean at 75mph it's running around the 220 degree mark - and then randomly dropping to 180ish (all completely independent of accel or decel) I'm seriously inclined to think checking the impeller and going ahead and replacing the thermostat that was just put in. I think there MIGHT be a combination now of not enough water flowing/thermostat sticking. I'll probably flat out replace the pump as it's OEM, and I've been experiencing low pressure for the duration of this problem.

They're wouldn't be any other passage ways in the block itself that could still be clogged, could there? I believe we got most with the ILM, but I'm unsure

Tiny
W_nter
Sep 15, 2011.
No, no passages clogged unless you used a lot of sealer which is a system crasher.
Start with the basics and check the water pump.

Roy

ASEMaster6371
Sep 15, 2011.
***Update***

Replaced water pump, hoses, and low coolant sensor over the weekend. Verifying if I still have loss of coolant, but so far just making sure all air is out of the system. Also haven't experienced fans automatically turning on, but that I have a feeling I might need to hard reset the PCM to get the fans back in the picture, but I swear this car is possessed sometimes (an experience I had with the brake lights)

Other than that though - the car is responding fantastically to the new pump - coolant temp is stable. I'm starting to be suspicious that coolant is disappearing, even with the replacement of the LIM gasket - after the last wild fluctuations, opening it up and there being significant loss - although I'm not experiencing puddling anywhere, or white smoke out of the exhaust. I'll post follow up once I isolate it.

What wold help in diagnosing that further?

Tiny
W_nter
Sep 20, 2011.
Definitely have coolant disappearing again. No indication in the drive way of where it's coming out yet. I just refilled 1/3 of a two liter - going to double check I got all the air out from this last weekend as the Low Coolant light is still bouncing back and forth.

Suggestions?
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Tiny
W_nter
Sep 22, 2011.

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