Thread: 2001 Grand Prix GT: possible multiple issues...

My stepson has a 2001 GP GT, 3800 Series II...first, two days ago, heading for the house, car overheats, find crack in radiator on passenger side of the car, near where hose attaches.

Replace radiator today, car initially overheats, replace thermostat, temp holds to about 185F, after idling for about 20 minutes. Take the car out of the driveway, drive no more than 1/4 mile, radiator has crack in same place.
Where's the pressure coming from to cause the cracked radiator?

Second: Car is running poorly. Rough idle, will not rev in park past 3500 rpm.

Suggestions?

Wow. My radiator never cracked but, my car would stay good on the temp 4 a while then start 2 spike up and down, coolant kept coming out of my radiator cap even tho i replaced it a few times, i replaced the radiator, hoses, stat, water pump and still the same thing. After i replace my lim gaskets, i never had a prob since.

Well i dont know if its all gp or just the supercharged 1 that wont rev up past a certain rpm on park or nuetral to avoid damage 2 the motor. My gtp wont rev past 4k rpm on park or nuetral.

Originally Posted by a98gtp4u

Wow. My radiator never cracked but, my car would stay good on the temp 4 a while then start 2 spike up and down, coolant kept coming out of my radiator cap even tho i replaced it a few times, i replaced the radiator, hoses, stat, water pump and still the same thing. After i replace my lim gaskets, i never had a prob since.

LIM=Lower Intake Manifold? What's that cost, and what' the time involved?

the gaskets 4 mine were like 50 bucks, its an improved design, better that oem. since i have a gtp, i had 2 remove the fuel rails, supercharger and the the lim, and what ever other little stuff that was in the way. since yours is just a gt it mite be easier. get a haynes manual from auto parts store, comes in handy. since it was the 1st time i ever did anything like that it took me like 3-4 hrs to take everything apart. like 1.5 hrs to put it back 2gether.

Originally Posted by Liquifire

Yes, you will not be able to rev the car in park or neutral past somewhere in the 3500-4k range due to the rev limiter on all Grand Prixs of this era. I am stumped on why the radiator cracks but I would get a new radiator cap and double check the hose that goes to the coolant overflow tank for obstruction. What type of coolant are you using now? Did you purge the system of air first before driving it after replacing the radiator and the thermostat?

I understand the rev limiter, which is what I expected. As for the radiator, we did not replace the cap, but will the second time around. Not 100% sure if there are any obstructions, and I don't know if we bled the system correctly. I can tell you that the hoses pressurized, and I noticed that the bottom part of the upper hose was hotter than the rest...did open the bleeder on the thermostat housing when we were filling it with 50/50 mix from Prestone....

Originally Posted by Liquifire

when you fill the radiator up leave the cap up and let the system circulate. keep filling it up as it circulates and this will allow the air in the system to leave through the open radiator cap. Do you have dexcool in there?(original orangeish gm coolant) or do you have yellow stuff or green stuff? The waterneck bleeder is there to help the system clear out any air bubbles in the system as well. Do this a couple of times. Get the motor completely up to temp while doing this procedure. Make sure that it gets up to temp, the thermostat gets up to temp and it all circulates properly. After all of this happens top off the fluids in both the radiator, and the overflow tank. Seal it all back up and run it. Did the fluid look normal when you did it last?

We will do that when we get another radiator...I know that my stepson had been adding water, but I don't know if he did it at the overflow tank (probably the right way) or at the radiator cap (which probably allowed air into the system)...does the pressure build to a point that it could crack the radiator if the cooling system is not bled properly?

Originally Posted by Liquifire

Which type of fluid are you using?????? green yellow or orange dex cool? If the cap does not allow the pressure bleed off or it is plugged to the overflow I would think it could build too much pressure, but I would think that a hose would blow off or something before the radiator gave out but I dont know. So both of these blew out in the exact same place? If you have some air in at the top of the radiator from removing the cap, that will not hurt anything. You could fill it in either spot and be OK(unless the overflow was plugged and could not allow coolant to get into the radiator thereby allowing the radiator to go low on coolant, overheat and crack. This is possible but I dont know how likely. But which coolant are you using or did you combine them? this is important to know...if you know what you are using, I can give more advice in addition to this.

We're using the yellow-green stuff...tell me what the difference is? I'm most curious...and yes, the radiators cracked in the almost identical places, next to the upper hose connection...

Originally Posted by Liquifire

green stuff is only to be used with green stuff and the yellow. The yellow is supposedly able to be mixed with any type and be OK. The dexcool is only to be used with dexcool. This is stuff that gm used from the factory. It is known to be corrosive if used with other coolants, or if air is in the system, or if it is not changed out at proper interval levels. The stuff will sludge up easy and make scum in your coolant system and eventually eat up your gaskets if not taken care of properly. I personally did a thorough flush, got rid of all coolant, and started over fresh with the green. It is up to you what you would like to do though.

I didn't understand your original question...so we're using the green stuff. I still really haven't seen an answer to the question about the radiator...how would I check for a leak? The only thing we've noticed is that there is steam coming out of the exhaust when the car is first started, but it doesn't smell sweet (of anti-freeze)...what about the LIM gasket replacement? Would that help?

If 2 radiators cracked in the same place I would look at the subframe flexing....the car will overheat and go into limp mode well before the radiator crackes for being overtemp. I think the subframe is flexing and exerting pressure on the radiator mounting points and causing it to crack. No coincidence that it idled fine in the driveway for 20 mins and then cracked in the same place 1/4 mile down the road. can you post pics?

Originally Posted by Liquifire

the only way to see if the radiator is leaking is to get it up to temp fully with the coolant level all the way up...you will see the leak if it is leaking, or at least evidence of the leak. It is normal for the exhaust to have steam come out of it for a little bit on start up. It is condensation built up in the exhaust which heats up and turns to steam. If it continues to steam while up to temp or running during the day or it smells sweet, then that is a problem. I still dont understand how you could have a radiator that went bad in the same spot twice. Are you positive there was a leak in both of them in the same area? I dont know how much the LIM replacement would help. Do you have any coolant which puddles on the intake on top of the motor while it is running? Does your oil look normal and is at proper levels? I would be more concerned about the radiator and what is damaging it. Please answer these questions and we will go from there.

Ok...the oil from the dipstick looked fine...no water droplets, no coffee w/creamer looking stuff...I have not noticed coolant puddling on top of the intake, but it;s worth looking at. I am positive that the crack/leak is in the same area on the driver's side of the car.

Originally Posted by Burbman

If 2 radiators cracked in the same place I would look at the subframe flexing....the car will overheat and go into limp mode well before the radiator crackes for being overtemp. I think the subframe is flexing and exerting pressure on the radiator mounting points and causing it to crack. No coincidence that it idled fine in the driveway for 20 mins and then cracked in the same place 1/4 mile down the road. can you post pics?

What subframe? When we replaced the radiator, we didn't miss anything, and didn't notice anything that would cause a flex...it seemed to be pretty solid once we put it all back together. What, on this car, is 'limp home' mode? I will get some shots as soon as the weather clears around here...rain right now...

Gentlemen, thanks so much for the help!!

Is there any possibility that a cracked intake manifold might be the problem, consider the pressure issues?

Here is that photo that was requested...

http://www.thepostnewspaper.net/radiator.jpg