Help!!!!!!!!!

Last August I started having my CHECK GAUGES light coming on occasionally.  The temp gauge would also indicate a higher than normal temperature.  I chemically flushed, power flushed, and backflushed the radiator.  Replaced temp sensor, cat convertor, coils (needed done because they caused the cat to fail), thermostat (1st a replacement 195 then a 180), water pump, and hoses.  Added a 'water wetter' to the new coolant.  The cooling fan works fine.  This was done over a few week period.  I can sometimes run for a few days without my TGP overheating at all!  But sometimes the temp will climb to 220!  Air bleed shows coolant only, no bubbles.  No coolant in oil.  No boil over.  No loss of coolant.  No smoke from exhaust.  Hoses are not collapsing.

This is all normal driving, no racing!  If it happened all the time I would suspect a failed component somewhere, but since it does it when it wants to (and I've replaced almost all the components) I suspect a 'floating' blockage somewhere in the system that should have flushed out.

Any ideas or suggestions????

I've thought about removing the thermostat and backflushing the engine with the radiator disconnected.  Am I 'grabbing at air'  if I try this?

Additional info was posted 26Aug03 under "Help...Check Gauge light".

Did you know there are two temp sensors? Is it possible the
radiator fan isn't moving enough air sometimes, weak motor?
what is ambient air temp, does it run hot even at night with
cooler air?

I didn't know about the second sensor.  Where is it?

Fan seems okay.  The light seems to come on just as it approaches 200.  It'll flicker, then go out, and come on and stay on.  It doesn't seem to matter if ambient temperature is 60 or 90.  With A/C on or off.  No belt squeal.  Sometimes I can drive a day or two with no light.  Yesterday the light came on when I started the car up first thing in the morning and stayed lit anytime I used the car.  Today it would flicker after the engine warmed up and then flash on and off most of the day doing errands.  I'd get back in the car after letting it set for up to 30 minutes and the light would be on for about 15 minutes of driving then start flickering again.

Whassup??? :crazyeyes:   Any ideas FORIDA_TGP or anyone else?

I didn't have much hair when I started, but I have much less now! :?:

the sensor for the actual temperature gauge in the cluster is located in the rear head on the driver's side bottom corner, it should have one green wire(not certain on the color but I've seen a few GP's w/ 3.1's and they all had green wires) coming from it going up towards the firewall...hope that helps!

The part you're talking about is the "Engine Temperature Sensor" and from what I've searched, it is located exactly where mfewtrail says it is but doesn't seem to apply to the 1990 TGP.  My GM manual doesn't list it, AutoZone and GMPartsDirect also don't list it.  I'll look for it anyway.

Anybody else have any other ideas?

Advance Auto Parts lists it. Here it is.

I just logged on to //WWW.ADVANCEAUTOPARTS.COM and they don't list that sensor for a 1990 Pontiac GrandPrix McLaren v6 3.1 Turbo.  

How did you find it?

Thanx for the feedback............. :)

Don't add water wetter to anti-freeze. It will do nothing for you and may possibly cause higher temps. Water wetter should only be used with clean distilled water. What % of mixture are you using water/anti-freeze? Too much anti-freeze and the water will not pull the heat from the mixture... 8)

Could be a problem with the catalogs for the 90. If it shows it for a regular GP then maybe thats how it was located.

How about your radiator. If its partially blocked from mineral growth it couldn't be flowing enough to cool properly.

Honestly, if you dont' have a chip, 220 is not really that hot. Most cars won't even have the cooling fan come on until 220 and the secondary until 230 or more.

It seems the check guages light is what is causing you the greif with the coolant. This is a common problem and is not specific to the coolant temperature. The light should not come on for the coolant till it reaches the red area at the very top of the guage. If it is coming on at any other time then is not operating properly. There is a fix for this.

Thanks for the input Chris and TGPilot.  You're probably right, it's not a real problem, just a 'pain in the a$$'!  Car runs great, city mpg about 18 and highway mpg about 30+, and can still lay rubber and pass about anything I've come across, so there probably isn't anything really wrong with my 'old cash hole'!

BTW I did find that 2nd sensor on the block!!!  It's not listed in my GP Service Manual!

I flushed the system again to remove the 'water wetter'.  Now I'll see if that helps at all (though I think it's just a light problem now!)

Bought the baby brand new off the lot in May 1990 and been using it almost daily since then (a few normal problems such as Xover, trans, and a few sensors, and about 4 sets of tires).

Again thanks for everyone's feedback!!  This forum is the BEST!

Right now I'm unemployed, but when I get a job I WILL donate $omething.

It seems you have covered the majority of possible causes for overheating, but let me add a thought or two.  Assuming that you DO NOT have any sort of head gasket failure, I would check the following...It is possible that over time, part of the radiator core may have become restricted, and not allow full flow of coolant to pass in front of the fan, this is also assuming that the thermostat is opening and closing at the proper times, cooling fan is operating at intended temp, water pump is supplying neccesary pressure, and guage is ACCURATE!  There are a few other factors, but more remote, you seem to have covered almost all of the bases, I just figured I would point out this one other point.  PS, I have another idea, but check this one first.

Wouldn't a head gasket failure have water in the oil or oil in the water and have a tendency to over pressurize the cooling system to where the radiator cap would 'pop off'?

The problem is not constant!  It's intermittant(sp).  I can run days without the gauge light flickering.  Othertimes it comes on when I start the car cold and stays on for a while, then flickers on and off the rest of the day.

Once I found out that there was a second temperature sensor, I replaced it.  With the new sensor installed the 'normal' temperature seemed to be higher.  I tested the sensor (thermistor) and found it running about 100 ohms lower than it should be.  I 'spliced' in a 150 ohm variable resistor and ran the car to operating temperature for 20 minutes.  I then adjusted the gauge to read 180F (the present thermostat setting) and now the 'check gauges' light will only come on when the temp reads 200+.

No water in oil, no oil in water, no 'boil-over', fan kicks in occasionaly usually at idle with air on, radiator has been flushed backwards and forwards at least twice, block has been power flushed in both directions, and the car is running GREAT!  As soon as I get a little extra $, I'll probably add a 'real' temperature gauge to check accuracy, but at this time I tend to agree with Chris A that the gauge cluster is probably showing age (a common problem with these beasties).  Any other comments are suggestions are still appreciated because I'm not 100% sure.

I don't like 'alerts or alarms' to show if there is no real problem!  If you follow the 'thread' you'll see I haven't missed too much.  (Probably over kill!)

the fan between radiator and engine should run 100% of time
when ac is on. the fan in front radiator/intercooler, comes on
only when extreme high presure in ac system detected.

At idle, air off, what temp does guage read when fan comes on?
I think it should be about 220.

My Son is actually having similar problem in 92 GMC Jimmy,
Is it possible to backflush a radiator with it in the truck?
He has a kinked heater hose, but he won't take time to work on
it. If that boy overheats and ruins a head gasket, he will learn a life
lesson!!!!

I haven't seen or heard my secondary fan kick in at all.  I don't know what the set points are for the fan switches.  Since my TGP hasn't really 'overheated'  (gauge has never shown more than 220F) I don't think I've had a head gasket problem.

I hope florida_tgp's son gets smart and takes the time to replace the kinked hose.  It's no biggie and is very cheap compared to the alternative consequences.  An ounce of prevention....  

The longest I've ever gone between cooling system maintenance is 3 years  :oops: .  Usually I do it yearly i.e. normal drain and refill system.  I  usually check for collapsing hose and leaks everytime I pop the hood.  I check my driveway for signs of anything leaking.  I wash the engine and engine compartment every other car wash.

Prestone has simple backflush kits to use your garden hose.  Available just about anywhere including WalMart.  According to my water bill last month, I used about 1000 gallons of water flushing the radiator and engine (or I've a broken water line to the house   :?: ).

"If you don't bleed on it, it won't work right".

Thanks for the feedback.