114k miles on my 97 Bon....best car I ever owned...until now. Service engine soon light started flashing yesterday, engine stumbling, missing, code 300-random misfire, checked the pcv valve and its soaked with what looks to be antifreeze. also after clearing code, I got a code for MAP which Im assuming is because the PCV is so wet. And yes antifreeze is dissappearing but not leaking outside.

So I take it its the upper intake??? Just a gasket or the manifold itself. If someone can please let me know what they think, I would greatly appreciate it. I'm pretty good with tools plus I have the GM manuals.

I plan on trading it in , in a few months.So I hope I can get it going for a littel while but dont want to spend a fortune..

ANy suggestions...thanks in advance!!!!

I wish I would have found this forum sooner!!!!

Forgot.SSE .. not supercharged

Yes, likely UIM failure, possible LIM gasket failure also. Sorry to say.... :( No cheap way to fix, but least expensive quality fix is to try and get a rebuilt one from Bob Dillon here on the forum, if he has one ready.

Best overall fix, IMO, is the APN replacement UIM kit. very reasonable for what you get, IMO.

Also, don't forget to get that new aluminum-framed LIM gasket and replace it while you are at it.

Here'* the best link I can give you for all the info you could need:
'95-03 Upper Intake Failure Info

That doesn't mean you can't ask more questions, lol.

I just did this with the APN intake. Check "All 3 ignition coils died at the same time" thread for pictures shortly.

Not actually that bad of a job, if you've got a 2nd person to help, and you are both mechanically inclined...

Most importantly, quit driving the car, and drain the oil as soon as possible. When coolant mixes with oil and circulates through your engine, it attacks the bearings and can cause premature failure of rod bearings, main bearings, etc. The longer the coolant is in contact with the bearings, the bigger problem this will be. .

There is a cheap way to get a quality fix for a failed upper, but it will require that you repair the upper yourself and that you are willing to wait a few days to get the parts you need in the mail. The parts will cost you about $15 plus $5 for some JB weld. Also, the sealing surfaces on your UIM must not be badly warped, so that it will seal properly when you are done. You must also replace the lower intake manifold gasket. From your description of coolant in the pcv valve, I would guess that it is the LIM gaskets that have failed. If you purchase the old, plastic frame gaskets from any parts house for the LIM instead of the better aluminum frame gaskets from a GM dealer, you can save another $20.

To do the job with a new APN upper, aluminum frame LIM gaskets and a new coolant elbow, you will spend about $200 in parts and supplies. To repair the old upper yourself, use plastic-frame LIM gaskets, and a new coolant elbow, you will spend about $100.

I am reluctant, however, to recommend you go the $100 route, because the difference between this cheapest fix and the best fix you can get is only $100. I understand how $100 can be a lot of money, but, if you consider that a shop might charge $200 for the labor, you are really looking at the difference between a $400 job and a $300 job. Even if you are selling the car, if you do the APN/Al LIM fix, you can honestly tell the buyer that he will not likely ever suffer from this common failure as long as he owns the car. That should be worth another $100 in the sale price.

I agree with Bill and donot cut cost with the LIM gaskets and the UIM replacement. I just did this job myself about two weeks ago. I bought a Bob Dillon replacement with a permanent fix for $62 delivered. The GM LIM aluminum gaskets were $56 and the elbow about $7. The UIM gasket was $30 from GM. Don't forget the loctite for the LIM bolts and get some black RTV sealant. For just a hundred more bucks you get a quality job and a permanent repair to a reocurring problem. Piece of mind should be worth a hundred dollars!

I had to get the car up and running as quick as I could so I went to local auto parts store for the UIM Kit. $140 which wasn't too bad. Unfortunatley they didnt have any LIM gaskets and I was pressed for time. Everything went fairly well following instructions and advice on here...When I lifted the manifold up there was coolant everywhere inside. A good 1/8' hole/crack in coolant passage under throttle body!
After done, very hard starting....got a bit nervous....but it started......ran rough while white smoke poured out of exhaust for a bit....but then cleared.

I changed the oil and antifreeze and also the spark plugs....they were really bad.


Starts fine now... mayby a little rough idle... but seems to be getting better...but....

Shifting hard when i first go...1 to 2.... and I think its running hot according to temp guage... but really havent had a chance to drive it too much....The hard shift bugs me.??? has me nervous.

When I recently had muffler chaged, I was told I should change the cat. conv. Short on cash at that time i Opted not too. Is it possible that is causing the shift. When the UIM failed, the check engine was blinking away while I limped it home so I thinking now may be the time for the new conveter??? Would it cause it to run hot and shift hard??
Any way to check it or should I just bite the bullet and get a new one?

I will change the LIM gaskets this weekend when I have time providing I can find them here...would that cause the hard shifting and hot running??
Any other suggestions????

How long did white smoke pour from the exhaust?

Oh, and get the aluminum LIM gaskets as soon as you can. They are really a lot better.

White smoke came out for about a minute,,,heavy...by the time I went around the block it stopped...
Someone had suggested that since I lost alot of coolant and which I added back, that there may be air in the system whuch is causing it to run hot... possible?? if so, how do i take care of that?

any suggestions on the hard shift?
thanks!

Here, read this Coolant Fill Procedure from TECHINFO above. Believe me, It makes a difference.