the stock lower intake gaskets are made of nylon and age poorly, i would go for a set of Fel-Pro aluminum framed gaskets so you don't have to deal with this again, if you tear it down and don't see a spot where the nylon gaskets have failed (which they most likely have) you have a blown head gasket and it's no big deal to pull the heads to replace the gaskets.

also DO NOT DRIVE THE CAR until you get the problem fixed, if you drive it you risk spinning a bearing and these motors cannot be rebuilt properly because of the way the connecting rods were made

if you need access to GM service information just pm me and i'll give you instructions on how to access it

 

I had a car that took me a LONG time to figure out it was a blown head gasket (I had to tag my GM guru to inspect it, once he told me what was wrong, I went to town fixing it).

- Started with the coolant temp getting WAY hot (like into the red). It would go down. I also noticed loss of heat while the temp was getting really hot. Change T-stat, problem continued.
- I was loosing coolant, on this car the loss with via the overflow bottle (on the N-Bodies, the overflow bottle is where the radiator cap is, goofy design). I could see fluid coming out of the cap after a commute to work. I thought the cap was no longer holding pressure, changed cap. No change.
- Pressure tested the cooling system, no problems found (no leaks, no loss of pressure).
- About a week before I tagged my guru, I'd start the car and it ran really rough for just about 2-3 seconds and I had BIG white clouds out the exhaust. I had a feeling I knew what was happening.

End result, the failed head gasket was allowing compression gases into the cooling system (this over pressurized the system, and caused the coolant to come out the radiator cap). As a result, it also blew the gasket on the side tank of the radiator (which, I replaced about 2 years prior and it had a lifetime warranty). Once I changed the head gaskets, I still drive that car today (put about 35K on it since that experience).

It was MONTHS of figuring it out. My guru said for the problem I was having, he was impressed I suffered NO loss of performance once it blew the coolant out the exhaust the seeped into the cylinder. I found a crack in the head gasket for both heads on my 3100.

There is a chance you could inspect the plugs and NOT see one goofed up. But with exhaust smelling sweet, that's the big clue. It's probably early in it's failure. What ever you do, don't put any "head gasket repair" garbage in the oil or coolant.

 

I ALSO OWN A 99 Z34.....MINE STARTED HAVEING A PROBLEM WHEN I TOOK IT TO THE CORNER OIL CHANGE JOINT AND THEY SUGGESTED A FLUSH...SO I LET THEM DO IT...HOWEVER, THEY USED ANOTHER ANTIFREEZE(GRREN) INSTEAD OF DEXCOOL AND MINE TURNED ALL MILK AND GOOPED.....WHICH EVENTUALLY BLEW OUT THE UPPER INTAKE GASKET AND ENDED UP HYDROING THE MOTOR.....SO I DID A COMPLETE FLUSH AND REPLACED THE UPPER INTAKE (SINCE ITS PLASTIC)....CAUSE IT GOT SO HOT IT WARPED IT......I REPLACED IT AND SHOULD HAVE DONE THE LOWER AS WELL (SINCE I ALREADY HAD IT APART).... BUT IT DID CURE THE PROBLEM....

I WOULD RECOMMEND A COMPLETE FLUSHING OF THE SYSTEM AND REPLACE BOTH UPPER AND LOWER MANIFOLDS...AND YOUR PROBLEM WILL BE RESOLVED...BESURE TO WASH OUT THE OVER FLOW (RESEVOIR)..REALLY WELL ALSO....

PS
MINE ALSO HAD 135,000 WHEN I DID MINE.....

ALSO 3800 ARENT KNOW FOR BLOWN HEAD GASKETS...



HOPE THIS HELPS !!!

 

This green vs Dex coolant was not the cause of your failure. THis information is incorrect (and sometimes spread as urban myth). Any GM car the "requires" Dex will run on "green" anti-freeze just fine (but a car that was not designed for Dex should NOT have Dex ever added). Almost, if not all, anti-freeze you buy in a parts store that claims "compatible with any color coolant" is green. Mixing those coolants may just discolor the coolant (not not make it milky). If coolant and oil mix, it will create a milky appearance. Dex can get sludgy if not flushed at regular intervals (but so can the green stuff, you just hear it happening more with Dex).

Odds are your intake gaskets were already on the way out and this was coincidental timing.

What blew your intake gaskets is the fact GM used nylon for a gasket material. It does not mater if you use green or Dex cool, any coolant, will destroy the nylon over time. The answer is to replace the nylon gaskets with the new/revise aluminum ones from Fel Pro.

As for the "warping" of your UIM, you either had another cause for that or someone gave you bad info. I do now the "stove pipe" from the LIM to the UIM in the 3800 is known to damage the nylon the UIM is made of. That damage can cause coolant to enter the UIM (which you don't want).

None of this is related to green vs dex. That is all urban myth (and a false one).

 

Now, I don't know if the gaskets failing on this car here had anything to do with the coolant used from the getgo. But i've seen that brown sludge crap myself firsthand. Its not oil or any other fluid mixing in there, its just flat fluid failure. And damn near impossible to get it all out of there.

My guess is the intake gaskets and possibly some of the other gaskets on this car were just made weak to save money. The california state supreme court agrees the sludge did mess things up though:

General Motors Class Action Lawsuit | GM Lawsuit | Girard Gibbs LLP

Its a good car. Its a shame they put sub quality components in it to save $50. Doesn't make any sense.

 

Old Dex cool (like early to mid-90's Dex) was a bad formula, proven it accelerates failure of nylon gaskets. It took years for those lawsuits to see the light of day and get settled. GM has revised the formula for Dex cool (I believe in the late 90's). Bottom line, a car made '99 and up running Dex is fine.
FYI - I have a friend with a '94 Formula Firebird, he's the only owner of that car, had Dex since the day he bought it, stored winters and it has about 70K on it. No sludge. The key element is flushing the coolant.

I too have seen the brown "sludge" you mentioned (looked kinda clay like sometimes). It's Dex cool that has NOT been flushed regularly like it's supposed to be. I have also seen green coolant get almost black in color and sludgy, again, not properly maintaining of the cooling system.

As for the gaskets made "weak" to save money.... GM has had problems with LIM gaskets in the 3100 (carried into the bigger 3400) since at least '94, if not further back. GM contracted Fel-Pro and Mr. Gasket to make the LIM gaskets, I have NO idea why Nylon was chosen, but it was. I'm not sure who GM chose first to make the gaskets, but when all the failures rolled in, they switched to the other guys (feeling the first company botched it). Well, another company making nylon gaskets (allegedly re-enforcing the gasket) still failed.

I know it's regardless of what coolant you run, as I have seen first hand GM 3100's that NEVER ran Dex have LIM gaskets fail the same way the alleged Dex cool gaskets failed. My Grand Am has had two sets of LIM gaskets since I owned it. I have owned it since '03, it has NEVER had Dex in the system during my ownership. I don't believe it had Dex from the factory either.

Bottom line, Dex is being over blamed for what really was a poor choice in gasket material.

Given the law suits GM has suffered, I don't think they would continue using Dex today if it was truly as acidic as people believe. There would be way too much risk involved.

 

Well thats true. Run a fluid past its recommended service interval at your risk. It seems this particular fluid failed really badly though. Thanks for the info.

 

well tks for the clarification..on dex coolant..........the afore mentioned.. I guess... "WAS" coincidental....go figure.....Just shocked that it all happened with such I'll timeing.....tks again for the clarification! srry for the "mis" information....