coolant leak around intake manifold?
 

99 Bonneville, 3.8 non supercharged, 55,000 miles.

Took girlfriends car into shop for oil change, coolant flush and tire balance and rotate.

Picked up car, shop said coolant was pretty low, and to watch for leaks.

Drove it home, parked it for 2 days.

Yesterday noticed a small puddle of coolant coming from drivers side of engine. Opposite water pump. ( I had noticed a few occasional drips from that area in the past, but it was only occasionally and nothing that seemed to be getting worse or happen all the time.)

Opened up hood, popped off plastic cover and noticed coolant pooled up on exhaust manifold and all around intake manifold gasket area. Area right where thermostat is located is dry.

Went back to shop to ask if they noticed anything weird and they said no, just that it was low on coolant, told them what I found and they said it was a common problem for the intake manifold gasket to start leaking on the smaller engines and occasionally on the 3.8's. Asked for a quote on what i described and I got $320.

Questions:

1. Has anyone else had a problem like this or heard of it? I've never seen water leaking from around bottom of intake manifold.

2. It looks like a pretty straight forward job to replace myself. Is it fairly simple and is there anything I should be aware of before I start?

Thanks!

it could be one of two things the T/B gasket could have started to leak or the Upper intake has failed.

DO NOT DRIVE THE CAR.

If the upper intake has failed and you try and start the car, and drive it or ever let it idle, it is bad very bad. The T/B gasket change is a rather easy and simple replacement feature. Could you please describe or give any more info that you have to fruther diagnose the loss of coolant issue

does it look like there is coolant dripping down from the throttle body area or does it look like there the coolant is leaking ontop of the block??

Drain the oil immediately. Like right now, even if it's 2am. If the upper intake manifold has failed, and coolant has entered the oil pan, it can rust the bottom internals in the engine.

Does the oil on the dipstick after running look contaminated? Milky? Read the Vin K Techinfo articles.

Those vin k articles are great! thanksonce again

the oil is brand new and looks fine, they just changed it same time as coolant flush about 3 days ago.
I drove the car max 2 miles home from the shop and it has not been started since.
mechanic said nothing about oil looking milky or anything.

I borrowed your engine picture to show where moisture is, just keep in mind, I don't have the turbocharger, just a black plastic cover covering the throttle body that bolts to intake manifold. Most of the coolant is in the back corner nearest drivers seat on the exhaust manifold.

http://www.billrae.com/engine.jpg

that is most likely the T/B gasket leaking. It is a simple fix, If you do a search you should find some good info

Re: coolant leak around intake manifold?
 

Occasionally?? From what I learned on this forum a 3800 might occasionally not leak. That is a pretty common problem from what I have learned. I just did mine a couple of months ago, but I had twice your milage. I replaced the upper plenum and gasket as I assumed the plenum was a victim of the infamous EGR "stove pipe" burn through. As it turned out it was not too bad. I machined a new stove pipe with a .050 clearance so it no longer touches the plenum and sleeve to prevent the problem in the future. The biggest problem I found was the TB gasket that is molded to the plenum was pretty flattend and was leaking much like yours is. The one bit of advice I can give you (if the '99 is like the '96) is don't even bother trying to remove the TB from the plenum til after you remove the plenum. You'll see why.

man the more i read the more i want to puke.......

i see no signs of breakdown on the outside of the plastic, looks strictly gasket to me, but will only know when i get it off.

You won't see any signs externally. I don't think you have enough miles for that though. yours sounds more like a TB gasket. I stopped mine for about 6 months and then slowed it to a trickle with the GM cooling sealer suppliment tabs. 4 tabs in the radiator will buy you time if you need it.

Ok, let's clarify a few points. First of all.....SUPERcharger. :lol:

Second, Bonnevilles aren't prone to leak in general. The 95-98 non-supercharged engines are prone to failure of the upper intake in the EGR inlet port area. It's rumored that 99 had an updated design, but keep an eye on it anyway. Yours does thankfully sound like a TB gasket leak. An hour fix for 10 bucks. Use an inspection mirror to see if it's dripping off the bottom of the plenum/TB union while idling hot.

ok, thanks again and sorry about the turbo charger slip.... :lol:

will let you know what i find.

a little update.

I haven't dug into the engine yet, Everyday I check the oil and I took a sharpie marker and drew a little line on the coolant tank to monitor coolant level.

I have not seen anymore leakage and the car has been driven about 4 miles a day.

The water around the t/b gasket seems to be drying up a bit except there is still a very small puddle on the exhaust manifold, but it seems to be coolant goo that coagulated there.

I plan to go to the car wash today with a can of degreaser and really clean up the top of the engine.

My hope is somehow the guys at the shop got coolant all over the engine somehow during the radiator flush and didn't completely clean it all off.

I check everything before she drives it and after and will continue to monitor this.

Very odd...

awesome, thanks!

Well, not good but not disaster yet either.

GF drove car around today, lost about an inch of coolant in tank.
Got wrenches out and went to work. Got t/b off and gasket looks fine. I also don't see any plastic degradation in the plenum either...

Bad news is the coolant appears to be coming from the gasket between plenum and intake manifold. Look at these pics and let me know what you think. In the last pic, the bottom right corner of the manifold is where i think the leak is the worst, as this is where the coolant was pooling up on the exhaust manifold.

What do you guys think????

http://www.billrae.com/car/car%20011.jpg
http://www.billrae.com/car/car%20012.jpg
http://www.billrae.com/car/leak.JPG

btw, the oil doesn't seem contaminated yet, but i will change it anyway when i am done.

that is what i looked like, the car has 55k miles.

also should i do lowers????

i really dont want to as really need to have it running tomorrow morning..

yes the sticker says delphi E, with a long number next to barcode

if you go to www.billrae.com/car
there are a few more pics of the engine, not much but might help.

I have an hour before advance auto opens, what do you suggest I get while I'm there??

upper and lower gaskets? t/b gasket?

please advise, thanks

I guess i have to remove the upper to replace the manifold gaskets....

can you use mspaint and draw some marks where i need to check for failure (not gasket failure but plastic failure)

thanks

awesome work, thanks.

will look at it in a few minutes as I yank it off

well, not cool, look what i found:

http://www.billrae.com/car/carfail%20001.jpg

the hole where the stove pipe goes thru the plenum is warped out of shape and has a deep gash in the side, it has this weird cardboard kind of coating on it, apparently as a feable attempt to insulate the plastic from the stove pipe heat. I cannot tell if it goes all the way through, as the cardboard coating is in the way. Should this hole be perfectly round?

So, you think that aftermarket plenum is the best answer? What about stove pipe mods.
I've read all the related threads and everyone has their own answer it seems.


Thanks for your help.

nevermind, got it.

everything off, just waiting for lower gasket to come in tomorrow

I broke the lower plastic elbow from the tensioner to the manifold, anyone have part numbers?

commo,now is the perfect time to check torque on the lower intake manifold bolts.I found the 2 "hidden " bolts a bit loose while doing my Dorman install.These are the 2 diagonally opposed bolts in the corners that are only accessible with the upper plenum removed.Also a good time to replace the rubber o-rings that seal around the injectors .I also used locktite blue on all intake and throttle body bolts removed as added insurance ,especially after finding some of the upper plenum bolts a bit loose while removing the factory plenum.Yea, it looks kind of ugly with all of the oily crud inside but I guess that's to be expected when crankcase vapors are being fed in one end and exhaust gas in the other.Good luck with the install.

commo,now is the perfect time to check torque on the lower intake manifold bolts.I found the 2 "hidden " bolts a bit loose while doing my Dorman install.These are the 2 diagonally opposed bolts in the corners that are only accessible with the upper plenum removed.Also a good time to replace the rubber o-rings that seal around the injectors .I also used locktite blue on all intake and throttle body bolts removed as added insurance ,especially after finding some of the upper plenum bolts a bit loose while removing the factory plenum.Yea, it looks kind of ugly with all of the oily crud inside but I guess that's to be expected when crankcase vapors are being fed in one end and exhaust gas in the other.----Oh yea, "HELP" brand(by motormite) plastic elbows should be available at auto parts stores on the racks with the rest of the "HELP" parts.I know my local Pep Boys and Carquest have them for 4 to 5 bux each.Good luck with your install

thanks for the tips.

I went ahead and took manifolds all the way off and decided to check the lower gaskets, well I have no idea what shape they were in as they peeled off with the manifold in pieces............

I got lucky and had every part in stock in this little town in Oklahoma except the lower gaskets which will be here tomorrow. So I spent the time cleaning the throttle body , manifold, and gasket surfaces.
I'm on my 6th can of throttle body cleaner i think....

I dropped 1 manifold bolt somewhere down beside the engine (not inside the engine) and can't find it so i'm going to pick one up at gm dealer and get the elbow, bolt and a thermostat with gasket there.

I'm also in need of a 1/4 inch torque wrench as mine doesn't go under 120 in .lb.

I am thouroughly pleased with my air compressor and air tools I bought only 3 weeks ago. It's so much easier then fighting with those bolts where you can only move the wratchet 1/20th of a turn at a time. I'm having fun with this and hope I get back up and running correctly the first time.

Just to make sure on torque settings, I have lower intake bolts at 11 ft lbs (132 in lbs) and upper intake at 89 in lbs?

Yes...your torque specs are correct. They are what I used in my 99 also!

Gang....Does this mean that the Delphi uppers are not exempt from the failure as we once assumed?? :oops:

plastic elbow was 10 bucks at GM dealer as was a new thermostat

latest info.

Got everything on and running. Had a few codes come up for random misfire but I cleared them and everything seems to be running fine now.

I have a small leak from the rear plastic elbow (one i didn't replace) from the tensioner to the manifold, Looks kind of cockeyed but I went ahead and ordered one to replace it (4 bucks) and it should be in tomorrow.

Changed oil, it looked fine and smelled fine but better safe than sorry.

One question for you, On the bottom front of the maniold, below T/B, is a sensor that was surrounded by heat tape, I had to remove it to unplug the sensor and don't have any to replace it, will this be an issue???

I also want to say Thanks Again for all the help you guys have given me. Truly helpful and much appreciated.

Bill

Thank you
 

I just wanted to say thank you for all the help I received from this thread, article K and jr 3800 thread regarding this repair. I had never attempted a repair of this scale and was able to pull it off and save big bucks due in large part to the help I received in this forum.

Please don't hold it against me that I am a Grand Prix owner ;)

Welcome to the club! We're glad that our vast amounts of information here were able to help you. As you've found, there's tons and tons of info on the L36 UIM issues.

However, in the future, please start a new thread instead of replying to a really old one. ;)