overheated but fans didn't turn on

[lectron44]

96 Lumina 3.1 (I had neglected checking coolant-no former problem)engine overheated while using AC on humid day/ no visible coolant loss/ no smoke at exaust, fans didn't kick on.

I immediately shut down, added coolant (it was really low), bled system, added aluma seal, replaced radiator cap, removed cover on one fan (relay-looked good.) I was told temp sensor might not have functioned since coolant was low, so I didn't replace - still have never seen fans run.

Neither my "low coolant light" or fans kicked on though the temp approached 260deg on dash. System seems to be cooling ok now, not overheating at all, but I am concerned about my fans not working.

Does anybody have the diagnostic map, electrical diagram, experience or info on tracing this? - thanks

[cadgear]

Because the PCM controls the fans, you should check all inputs that would require the fans to run. The AC request should almost always kick on the secondary fan just to keep the condenser at a decent temp. The ECT has three wires, two for the PCM's purposes and one that goes to the dash guage. Its possible that the PCM didn't see the correct temperature and therefore didn't kick on the fans. Try running fused +12v to each fan to verify it does indeed work.

As far as the low coolant light, that sensor might be stuck. The amount of crud that builds up in a cooling system could potentially stick the sensor in the 'full' situation. My personal experience with these luminas is that the dash is somewhat wildly inaccurate; wheras midway would be 180 degrees, I note that most run about 1/3 to midway. Normal operating is roughly 200 on these, not via specs but real-world.

Although my personal preference is to verify, repair, or replace every component involved in an accident of any sort, most of the time verification is all that's needed. Ensure the tstat didn't stick closed, isn't restricted, the ECT reports to the PCM *and* dash correctly, the level sensor is clean and tests out good, etc. Overlooking or thinking something is unrelated usually means that the component in question is the culprit. Murphy's law of automechanics.

Some unrelated questions, are you the original owner? Ever flush the cooling system/have it done? Might wanna do that about now. If you haven't had the lower intake done already, definitely get it done now or shortly.

[cadgear]

Just thought of one more thing. Bulb check on the dash? Make sure that you've got everybody reporting for duty before you jump into the engine bay.

[lectron44]

Cadgear,
Thanks for the help. I am not the original owner, I bought it about 2 years ago with 140k long distance miles. It had been well maintained. You are right I haven't been a coolant flusher.

The "lower intake done?" - I don't (though I should) know what that means. Do you mind expanding on that.

Is there a low budget way of getting the wiring diagram (is it available on the web?). If not I have a mechanic friend/customer I can go and photograph from the big manuals. I have a small manual for this car but got a taste of the big manuals last week (had two borrowed trying to trace out a cruise problem) and got spoiled. They didn't happen to be the right ones for electrical diagnosis on this problem, and I have already returned them.

I can of course test the fans themselves, just not sure I can find those other components and proceed with conviction without a good guide.

Thanks

[cadgear]

The lower intake gasket failure is a common (if not guarenteed) problem on the later 3100 V6 engines. What happens is the gasket breaks down around the coolant passages in the lower intake manifold, which will let coolant out one of three ways: a) Outside of the engine, not always visible on the ground; b) Into the crankcase, obvious signs like oil sludging would be present; c) into the intake path, where it gets burned in the cylinders. The last might not *always* produce white smoke, especially if it is a slow leak over a long time. However, as in my case, it would pool in a crevice in the block and evaporate without a trace but with a strong smell of coolant.

I hear alldata.com has things like that, but I've never checked it out; I have access to shop manuals and GM Service Information so I never really bothered. Though the first thing I do when I get a new/used car is go out and spend $15 on a Haynes (or chiltons) manual for the car. Great low-end approach at fixin' stuff. I took it a step further and bought a set of 99 shop manuals for my Lumina, just in case. Not a bad investment, though definitely not for everyone. I'll help out where I can; I had a headache of a time tracking down wiring when my dash guage was inop while the PCM read correctly.

[lectron44]

Cadgear,

Well, I thought I had a little time but I noticed the temp gage was fairly erratic and my friend looked at it tonight - coolant in the crankcase. I'm planning on calling the mechanic tomorrow.

Thanks for your help

[jeffcoslacker]

Originally Posted by cadgear

. My personal experience with these luminas is that the dash is somewhat wildly inaccurate; wheras midway would be 180 degrees, I note that most run about 1/3 to midway. Normal operating is roughly 200 on these, not via specs but real-world. .

I can verify this

Overlooking or thinking something is unrelated usually means that the component in question is the culprit. Murphy's law of automechanics.

.

So true.....And like I always say, when the customer says "It can't be ______ , because I just had it fixed", they usually just told you what the problem IS.

[lectron44]

My friend referred me to a mechanic about 2 miles from here. He had me change the oil and filter and drive there with the radiator cap loose.
It seemed to do ok that dx - no overheating or noise. He's supposed to do it tomorrow. I like the looks of this guy - neat shop. He said this is pretty common.

I'm pretty sure the engine didn't ever get too hot, but I hope the bearings are ok. Time will tell.

Thanks for the counsel.

[lectron44]

My wife picked up my car at the mechanic's yesterday, and actually the bill wasn't as much as I thought - 4 hours. The "check engine soon" light is even out!

Today I stopped by to ask a question about the cruise and the guy pulled out the gasket they replaced - it wasn't a very big break, but enough.

Thanks again for your wisdom in this. I'm going to post a thread now and try to get my cruise fixed. Thanks again

[chris8727]

Sorry for my ignorance but what does PCM stand for ?

What about ECT ?

My sisters 95' Lumina had 2 fans not working. Her A/C compressor is fried but bothe fans come on if they are jumped.

Should I check the Fan Sensor / Temp Sensor near the rear of the engine by the EGR Pipe ?

Could it be the Electronic Control Module ?

Any suggestions are greatly appreciated...

[dwalmop]

(PCM) = powertrain control module