Coolant System Problems

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i'm having a problem with my 95' pontiac grand am, and was wondering if you could help. i've never had a problem with this car over-heating (or anything else, for that matter).
i was driving down the highway and all of the sudden the temp gauge went way up and my car overheated. i let the engine cool, added coolant since some had boiled out, and went to the nearest gas station. the next day i took it in and got the thermostat replaced, after having found out that the coolant system was holding pressure and because of this and the fact that there was no steam in the exhaust or milky color to the oil decided that it wasn't a head gasket problem. on my way home from having the thermostat replaced, the temp gauge went way up again, so i took the car back in. they found that the fan was kicking on when it should, and when the car was just sitting there, it has no problems cooling down when it should. in any case, the temp gauge inside fluctuates quite a bit, whereas the computer temp sensor gives the right temperature, and the fan kicks on at 226 degrees when it should. so my question is, if i haven't flushed the coolant system for a long time, could some line be clogged or something, causing the coolant not to flow when it should?? any ideas on what could be wrong given that
(1) the thermostat was just replaced
(2) the fan kicks on when it should at 226 deg.
(3) the coolant boils over at highway speeds and sometimes in the city,
but when it's idle, no apparent problems
(4) the system's been bled so there should be no gas in it (until it freaking

thanks a lot for your help.


posted by  ASBk

Checked the water-pump?

posted by  88GrandPrixSE

Seems like you might have some clogged tubes in your radiator. Warm the engine up all the way and physically put your hand on the fins of the rad, being careful not to burn yourself, see if there is a differnce in temp between the top tubes and the bottom tubes. If there is then you need a radiator. The water pump would show up at idle as well as at high speeds and might be but probably not your problem right now. :2cents:

posted by  srober32

Thanks for your :2cents:
I'm getting a hi-pressure flush tomorrow w/ new thermostat. Hopefully that will take care of any clogs. It's cheaper than getting a new radiator, anyway. ~$120 (w/ labor) compared with ~$220 (w/out labor).
Will let you know what happens.

posted by  ASBk

If the radiator is clogged badly enough to prevent water flow, the only recourse if it cant be cut open and rodded (the radiator shell being made of plastic as most new ones are is) to replace it.

Warm up the car hot enough to get the thermostat open. feel the upper radiator hose. If you dont feel pressure your water pump is probably in need of replacement.

posted by  tbaxleyjr

i'll check the pressure like you said on the water pump.
the guy who was going to flush the system didn't, because now he suspects it's a head gasket problem (and he doesn't do head gasket work - does that mean he's more trustworthy, or less?). he found a stain on the water pump, meaning it had leaked before. and he found an intake leak (what's that?). he noticed, and i've lately noticed, that when he started it up it shakes a bit until it warms up...especially if it overheated just before the engine was turned off last... which he said probably means there's an external leak (where the engine gases leak into the coolant, and then when you shut the engine down the coolant leaks back into the engine).
how does this sound, other than it's the last thing i wanted to hear? :doh:
any other ideas?


btw, the full specs: 95' Grand Am V6, 3.1L, with 160,000mi.

posted by  ASBk

3.1 motor.. most likely a head gasket. It doesn't mean he's not trustworthy if he doesn't do heads, it means he's a crap mechanic if he even is one. Just because there's something on the water pump doesn't mean it leaks, it could be anything on there. Most vehicles leak a certain amount of something over-time.

Intake? Intake manifold? Or the Plenum (the part of the motor that has 3.1 Multi-Port FI embossed in it)? Intake manifold is a severe fix, plenum isn't. That's what transfers the air to the cylinders. If it's a head gasket, all that will be fixed at the same time anyway.

If it studders when re-starting, that's not an external leak, that's in internal leak. That could be due to a blown head-gasket leaking coolant into the cylinders so it won't fire at the start until it gets it all out.

Have you noticed any coolant loss? Have you noticed any oil in the coolant or vica-versa? Any exhaust fumes in the engine oil dipstick? Sweet smelling exhaust? Those are all signs of a blown head gasket. The 2.8 and 3.1's are very famous for head-gasket problems so that's probably what it is. Lots of money to repair, just hope it's the front head.

posted by  88GrandPrixSE

This has been a problem for a while, because you have tried things like thermostats. The rapid rise in temp is steam caused more than likely a leak between the water jacket and cylinder.

Replace gasket and remember Hylomar is your friend.

posted by  Wally

really, it's only been a week as of today (since I began this post).
i work fast.

today i'm having a chemical diagnostic on the coolant (far as i know, turns blue if engine gases leaking into coolant) to see for sure if it's a head gasket prob.

posted by  ASBk

I know those 3.1's are famous for plenum/intake water jacket leaks. Don't jump on the head gaskets if your coolant does turn blue, check out the intake first, you might save yourself some trouble.

Good luck. at least you don't have the quad 4. :)

posted by  carls47807

That isnt true. Not always anyway.

posted by  DodgeRida67

is that similar to permatex aviation form-a-gasket?

posted by  BanffAutoSpa_ap

[QUOTE=88GrandPrixSE] Most vehicles leak a certain amount of something over-time. [QUOTE]

like over 10-20 years or?....... cuz besides natural oil burning(which could be fixed with CSRV) my car doesn't leak anything ever period, unless a gasket just happens to blow out or weep, in which case i replace it then and there.

posted by  BanffAutoSpa_ap

I mean there's always oil or coolant on the block (which means it leaks) on especially older cars, may it be past a gasket or past the frost plugs, that's all i'm saying.

Well.. To take out the head it's only another 8 bolts (for the front, you can easily sneak it out)... so... why would you just replace the intake gasket and hope it works and pray you don't have to put another 5 or 6 hours of labour into it and have to take it apart again. Replace the head gasket, or both of them. They're more known for their head problem anyway, rarely have to replace an intake gasket on them, I'd say a good 85-90% of the time it's the head gasket over the intake gasket.

posted by  88GrandPrixSE

It was the head gasket. I had it replaced and it works better than ever. Thanks for your help.

One symptom that I didn't realize was probably related is, ever since I got the car (2000), when I drove up hills it sort of shook and didn't seem to burn the gas that I gave it. I assume this was because coolant was getting into the cylinders. That's a long time to have head gasket problems though, isn't it (5 years without any overheating)? I thought they went out all at once.

Anyway, the rear head gasket was totally blown and now it's fixed.

Thanks again everyone -
ASBk :clap:

posted by  ASBk

Permatex Hylomar HPF or their copper coat spray. Not a gasket in a can, but a dressing compound.

posted by  Wally

depending where the head gasket is cracked,it could cause a coolant or compression problem.

posted by  the lobster

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