99 LeSabre 3800 3.8 coolant leak? Head gasket? Lower intake gasket is leaking.HELP!!

[chubbygoatboy]

I am working on a 99 LeSabre with the 3800. It has NEVER been overheated. But has started loosing coolant. I pump up the cooling system, and I find that the lower intake is leaking around one of the bolts. OK, so I need the lower gasket set, no problem I have done a few of these. BUT, if I start the car while the radiator is pressurized to about 10 psi, and I rev the engine, the pressure goes up slightly during the high RPMS, but as it comes back down to idle, the pressure goes up quickly on the gauge. Is this normal, or do I have a bad head gasket, or cracked head? I have been told by several people that the head gasket rarely goes on these. Is that true?? Any help is greatly appreciated!! THANKS

PS Yes, it still has Death COOL in it, but it won't after I am done with it!!

[LeSabre97mint]

Hello

I would get the coolant tested for Hydrocarbons. If Hg's are in your coolant, most likely, your headgasket(s) (or other gaskets that have Hg's in their passages) are bad because of the increased psi in the coolant system.

[chubbygoatboy]

Thanks for the info. I do not have the kit to check for hydrocarbons, but I think I can borrow one. I was hoping for a definitive answer concerning the pressure buildup. Is it normal for this pressure to build up as I described in the first post?? Any other answers are welcomed!!

[maxwedge]

Originally Posted by chubbygoatboy

Thanks for the info. I do not have the kit to check for hydrocarbons, but I think I can borrow one. I was hoping for a definitive answer concerning the pressure buildup. Is it normal for this pressure to build up as I described in the first post?? Any other answers are welcomed!!

More commonly here is the upper intake failure with the egr burning thru to the coolant passage in the manifold, pull the throttle body and look at those 2 passages, the exhaust crossover may affect the pressure but normally there is no egr under the circumstances you are checking this.

[chubbygoatboy]

Thanks for the info!! I have decided to go ahead and replace the plastic plenum anyway. It looks kind of warped up inside, and it is not worth it to mess around.

[animekenji]

Common defect in the Series II 3800. They mounted the hot EGR valve on a piece of plastic not designed for extended periods of extreme heat. It usually starts as a slow coolant leak but can end up with large volumes of coolant being dumped into the engine. This can really suck if you're tooling down the highway and get a hydrolock. Internal engine parts can break and if the coolant gets down into the oil pan, it's all over. The highly polished and finely fitted crank and bearings will corrode and eventually sieze, even if you change out the contaminated oil and replace it with fresh. You are catching the problem early, so find out what you need to know to replace the intake before this gets worse. I am not certain if the GM part from the dealership has been redesigned or not. I know a company called Dorman makes a part without the coolant passage, but I think you need to replace the lower intake as well (that coolant has to be re-routed someplace, right?). The series III engines use an aluminum upper intake, so GM has acknowledged the problem, in their own way, even though they won't fix it under warranty, like they should.

[maxwedge]

Originally Posted by animekenji

Common defect in the Series II 3800. They mounted the hot EGR valve on a piece of plastic not designed for extended periods of extreme heat. It usually starts as a slow coolant leak but can end up with large volumes of coolant being dumped into the engine. This can really suck if you're tooling down the highway and get a hydrolock. Internal engine parts can break and if the coolant gets down into the oil pan, it's all over. The highly polished and finely fitted crank and bearings will corrode and eventually sieze, even if you change out the contaminated oil and replace it with fresh. You are catching the problem early, so find out what you need to know to replace the intake before this gets worse. I am not certain if the GM part from the dealership has been redesigned or not. I know a company called Dorman makes a part without the coolant passage, but I think you need to replace the lower intake as well (that coolant has to be re-routed someplace, right?). The series III engines use an aluminum upper intake, so GM has acknowledged the problem, in their own way, even though they won't fix it under warranty, like they should.

Actually Dorman's manifold is reinforced in the problem area, not eliminated.

[happydog500]

I don't know if it's true or not, but I was told from one mechanic that the new ones (for the older) you get from GM are reinforced also.

In fact, he said he's done a lot of these and the GM ones are now better then most aftermarket ones.

With GM knowing of the problem and not fixing peoples cars, I don't know what to do on mine. Get an aftermarket or a "new" GM intake.

[maxwedge]

Originally Posted by happydog500

I don't know if it's true or not, but I was told from one mechanic that the new ones (for the older) you get from GM are reinforced also.

In fact, he said he's done a lot of these and the GM ones are now better then most aftermarket ones.

With GM knowing of the problem and not fixing peoples cars, I don't know what to do on mine. Get an aftermarket or a "new" GM intake.

Talk to someone in the dealership, ask them if the manifold is updated or improved in some way, they should know.

[RDizzle109]

On a cold day I would go out start the car hold your foot on the brake and put it in drive, next rev the car up to about 2k RPM's for about 30 seconds (wont hurt the torque converter), then shut the car off. Open up the radiator cap if you got pressure blowing out most likely the head is cracked should be any pressure in the system on a cold start. Also check for oil on the rad cap. Beside the crappy plastic plenum on these 3800's that engine is pretty indestructible I'd be surprised if the heads were cracked or leaking.

[maxwedge]

Welcome to AF, please check the dates before posting this is a dead 3.5 year old thread, thanks.