Ok... I guess my question is which are the most likely culprits of fluid leaks on a '94 Transport with the 3800 Series I engine.

The one that has me very concerned is a very fast coolant leak. There is obviously a leak on the intake manifold near throttle body, but there's obviously another -much bigger- leak toward the back of the engine. The coolant is dripping from the driver's-side rear cradle mounting area, if that helps. I know the intake manifold gasket (the one between the upper and lower parts of it) fails very often on Series II engines. Are Series I prone to the same thing?

Beside this, the engine leaks oil and transmission fluid. Not too much, but enough to ruin the driveway if you leave the car there. Other than the valve covers, is there any other usual place to check for oil leaks? And for ATF?

Finally, this car has another annoying "detail": under some circumstances, that I have not been able to determine completely, the engine stalls. This happens when the car is still at red lights or intersections, even if I put the transmission in neutral. Any idea what should I look for first?

Thanks!

BTW: I checked the tube nipple on the intake manifold, and it looks like it has been replaced already with the metal one, and I don't think it's leaking. Ideas?

Engine light coming on? Could be an old fuel filter & not sure about your engine but a bad IAC can cause problems and or a coolant temp sensor. Should check out some spark plugs too. Your engine is not known to have intake coolant leaks like the 3.1 or 3.4

LMP: Do you mean the heater hoses for the rear of the car? I thought those were used on Canadian models only. I'll try to check anyway... It's just so difficult to check that area...

'96: The check engine light is on, indeed. My car has the ODB "1.5", though, and the person who tried to pull the codes seemed a little less than competent at that, so I guess I'll have to check that again. I found (and replaced) some cracked vacuum hoses, but I have the alternator out of the car (broke the terminal on the cable that goes to the battery :( ) so I can't check if this made any difference right away.

I know the '94 Series I are not supposed to have intake leaks (these have an aluminum lower intake and plastic upper), but there's coolant collecting on the spaces on the lower intake in front of the throttle body... so I guess the gasket between top and bottom of the intake manifold just failed. I can't believe so much coolant is escaping from there, though.

The arrow point at the source of the visible leak... it's the hidden one that is giving me problems, though :)
http://i35.tinypic.com/aln7zk.jpg

Jarl:
I had a coolant leak in that location by the EGR valve on my 95 TS with 3.8..intake manifiold gasket leak. When I changed mine, it was loosing about a liter a month of antifreeze. A simple pressure test shows that clearly.
As far as the rear heater hoses ( and the associated valves) they are installed on all vehicles with optional rear heaters, not just Canadian cars ( altho all Canadian cars had them)
Jeff

Thank you for confirming this, Jeffry. So the leak was on the gasket between the two components of the intake manifold, right?

If I were to run the car as it is right now, I bet it would leak a liter in one hour, or maybe even less time. My impression is that it is too much for that gasket, but I'll replace it anyway. How hard is it to replace it? Do you have a link to a good thread or site with the information, or you followed the service manual instructions?

I know there was a TSB regarding the intake manifold of several models, but I don't know if this particular model was affected or if the information on the service manual is still valid.

Also: I checked the options list inside the glovebox, and according to it my TS doesn't have the rear heater option.

J

[Edit: I found this: http://www.youtube.com/watch?v=iVdN627dtx0 ... Interesting, but doesn't explain the full thing...]

Jarl:
I had a coolant leak in that location by the EGR valve on my 95 TS with 3.8..intake manifiold gasket leak. When I changed mine, it was loosing about a liter a month of antifreeze. A simple pressure test shows that clearly.
As far as the rear heater hoses ( and the associated valves) they are installed on all vehicles with optional rear heaters, not just Canadian cars ( altho all Canadian cars had them)
Jeff

Yes it was leaking between head and manifold. At 1 liter her hour, that does sound a bit more than just a gasket, but could be possible. Other area would be frost plug/block heaters to look for. I still think having the sysytem pressure tested will pinpoint your problem and possibly save needless work. Pressure testers can be had for the $100 range or perhaps you could borrow one.
Changing the gasket was pretty straightforward, except the manual says not to take the upper plenum off unless you are changing parts. I spent a day and a half trying to get the manifolds off as an assembly before giving up and removing the upper plenum then the lower manifiold..in about a hour and a half. many members have strongly cautioned against using aftermarket gaskets to put the engine back together, they just don't seem to last as well as actual GM parts. Also, while you are there, it would be a great time to change heater hoses, you can actually get at them!
Jeff

I'm sorry I think I missed something :(

On the attached image (from Autozone repair guides), the green color is where the coolant is pooling (above the lower intake manifold), and it's apparent the coolant is leaking between parts 163 and 164 (between the lower and upper parts of the manifold). Are you saying the leak actually comes from the gasket between the lower manifold and the head (#113 on the image)?

I thought the gasket that needs replacement is the one between the two parts of the intake manifold (not shown on the image). It looks like the P/N of that gasket is MS95830 (Felpro).

http://i33.tinypic.com/33urath.jpg

The gasket:
http://info.rockauto.com/Fel-Pro/MS95830_TOP.jpg

Yes, on my 95 it was the failure of the gasket #113 that caused my leak. At first I thought it was the thermostat gasket, and you could see coolant in the nooks and crannies of the lower manifold, but once a pressure test was applied, it was easy to see where the problem was. Wind at road speed blows oil and coolant leaks all over the place, and there really wasn't, in my case, much of a leak at idle, engine needed to be working for it to become apparent.
Jeff

If the gaskets have never been replaced on this motor, you need to go ahead and replace them.. The lower gaskets should run about $20-25, and the upper to lower gasket should be about $15..

Thank you for keeping the thread alive :)
I don't know about the past of this car. It looks like it has been neglected somewhat before the previous owner decided to have some stuff fixed, but I don't know if gasket #113 has been replaced. I agree I should change it, but with my luck I wanted to keep my intervention in the car to an absolute minimum, and taking it to a mechanic is not an option at this time.

Jeffry: I'm afraid I didn't mention something very important: the leak happens even at idle. I'm fixing other things on the car (interior stuff) and I don't drive it much... just a few miles every other week to keep the battery charged. The last time I looked under the car -after being parked a day or two- I saw a large pool of coolant on the floor, and when I started the engine to see where it could be coming from I saw the large amounts of coolant dripping quickly under the car, around the driver side rear cradle mount. The pool of coolant on the lower intake manifold has always been there and the area under the throttle body looks wet, so my assumption was that it came from there. I might be wrong, though...

I think your assumption may be right... If its leaking near or around the throttle body the dribbling coolant would fall on the drivers side of the cradle.. so you may be onto something..

The areas I circled in the pic below is where the upper to lower gasket is prone to leaks.. as well the Throttle body gasket can leak too..
http://img.photobucket.com/albums/v294/Jr3800/1995%20Pontiac%20Transport/Transport18Rockerinstall019-1.jpg

Great... I guess... :D

I already bought the lower intake gaskets this afternoon, but of course there's always the option of returning them. The question is: is it common for '94 3800 Series 1 to require these lower intake gaskets replaced? If we were talking about a newer 3.1 or 3.4 I wouldn't doubt it for a minute, but I have learned the hard way the "if it's not broken, don't fix it" (BTW: What are the chances of screwing up something big time while replacing the lower gaskets? I have been working on cars for years, but I have tried to stay away from the engine's guts from day one :D)

Assuming I decide to change the gaskets: the instructions for the lower gaskets (Felpro) say not to use any kind of adhesive, but all the information I find on the web says otherwise. Should I use RTV when installing the gasket? If so, does it need to be the "high temperature"-"sensor-safe" type? What about the upper gasket (Felpro as well but didn'tcome with instructions)? Should I apply RTV to it as well?

Thanks!

We'll start with the upper to lower gasket first... This gasket will be install dry, use no adhesive at all.. You may consider using Medium grade threadlocker( Blue ) to help keep the bolts from backing out.. When you go to tighten the upper intake I believe it should be 7 Ft lbs, what ever you do try not to exceed 10 ft lbs.. Good and tight with a 1/4 " Ratchet will do the trick..



Onto the lower intake gaskets..

Some will look worse than these, some will look better..
What you will notice is a crack in the gasket as it has degraded to the point of a coolant leak.. Some of the leak made it to the outside of the motor, the other part of the leak was wicking over to cylinder # 5 port front bank.. Look at the pic and you'll see the nasty looking port of the intake gasket..
http://img.photobucket.com/albums/v294/Jr3800/3800%20L27/DSC03539.jpg

The gasket on the rear side doesn't look bad, but it was seeping coolant to the outside..
http://img.photobucket.com/albums/v294/Jr3800/3800%20L27/DSC03544.jpg

No matter what, being that the engine is a 94 I would replace those gaskets.. The front gasket off the motor I was working on crumbled when I took it off... I had a good idea that that would happen so i had the lifter valley covered with towels to catch anything that might fall in..

For the lower gaskets, if they didn't come with a tube of Silicone black( sensor safe ) then I would use Permatex Ultra Black ( High Temp sensor safe )... Once everything is clean and ready for the gasket install, add a good dab of the Ultra Black at each corner of the block and head and set the end seals in place, then add those same dabs on top of the seals, set the gaskets in place( they have set pins ) and add those small dabs again... From there you will be able to install the intake..

Some of the cross brackets for the alternator and power steering pump will have to go.. Under the alternator will be the bypass hose / heater tube.. The metal tube is held in place with a 15mm nut, its location is under the power steering pump( wish I had a pic for you ).. The tube is in the intake with a 10 mm bolt... You may have to fight that one out of the intake, but be careful as you don't want to break it... Your intake kit may include the O ring for the tube...

If I could be there to help you, you'd see how easy it really is compared to other cars/ vans...lol... I'd rather do gaskets on an old 3800 Dustbuster anyday over a 3400 U body van( I still have scars from the 3400's )

If you have any other questions just ask..

Ok... here I am, with my '94 in pieces. Or at least trying to...
How, for Pete's sake... HOW do you disconnect the heater pipe from the left side of the lower intake manifold???:banghead:

Until now everything has been almost smooth, and I think I already identified the source of the leak (pictures later). But the @#$ heater pipe doesn't want to come out. It doesn't even bulge...

What I am missing here? :confused:

BTW: Big thank you for your previous post!

As long as you have made sure you removed the 15mm nut that holds the Pipe to the Tensioner bracket( under the power steering pump, there is a 15mm that holds that tube... Also I am pretty sure you already removed the 10mm bolt from the Tube on the intake manifold... The tube can be a PITA... If you have a skinny flat blade screwdriver you may be able to tap it between the tube face and the manifold and be able to pop it out that way.. Thats usually how I have to remove mine as they want to hang onto the corrosion..

Any other questions, please ask..

If you can't get the pipe off I may be able to snap a few pics for you tomorrow afternoon..

Thank you for all your help...
I was finally able to remove it by prying between the manifold and the bracket on the pipe (the one used to fix it against the manifold).

What I found is that someone had already changed the gaskets, and apparently had overtightened the screws crushing the plastic part around the coolant passages. At least that's what it looks like. The interesting thing is that I found that the right rubber seal had disintegrated, shredded in pieces, and there was a large amount of oily sludge right underneath it, above the transmission. I hope that was the main oil leak. THANK YOU all for talking me into changing the lower intake manifold!

Now I need to clean the mating surfaces, but it looks like it going to take some time... any trick/magical product for doing this?

Also: there's some sort of cover on the right of the lower intake manifold, held in place with three bolts, and it looks like there's a coolant passage behind it. Has anyone had a leak around this cover?

as for cleaning, I like to have some small rags to stuff the ports in the head( intake ports ) to avoid getting anything into the combustion chamber... and I like to have the Lifter valley covered with a towel, again to help avoid any debris... From there I used a scraper first, followed by a cookie( 3M Abrasive pad ) on my air angle grinder.. Followed with Acetone or Brake cleaner to clean the metal of any oils..

The cover that you are referring to does cover a coolant passage... Its not common for that cover to spring a leak... And about the only time you'll ever get a gasket for it is in a head gasket kit.. You might be able to get that from a dealer, but I have yet to see that cover leak on an L27, Thats not to say it could never happen, just simply in all of the years I have messed with 3800's I have never seen one leak..

as for the lower gaskets, yes they can be overtightened and become crushed.. This is the reason you will not want to overtighten the bolts.. Take the time to clean the intake bolts and use some Medium Grade Thread Lock( Blue ) when installing the bolts so that they will not back out..

Being that you have made it this far you must be Mechanically inclined..:) And your saving a good chunk of $$$ too..

Hmmm... Let's assume for a minute I don't have an air angle grinder... :) Would a fine sandpaper (400-600) or a dremel tool with a small wire wheel work? I applied a Permatex chemical gasket remover to one of the surfaces and, while it works wonderfully on the intake passages, there are some areas around the coolant passages that look darker, and are raised a bit. They look different than the residue from the gasket elsewhere...

I was wondering how on earth did GM dealt with the slight corrosion on the mating areas, since they say not to use abrasives or scrapers...

Yeah a wire wheel will work as well.. You might have some pitting on the heads where the coolant ports are... You could hit them with a little sand paper to get a better smoother surface.. I am lazy and use air tools all of the time, thats where the air angle grinder comes in.. I takes a minute to get the head/s good and clean.....LOL... Even a green scotchbrite pad should work..

The corrosion I try to get as smooth as possible.. But if you feel there is a little more pitting than you feel good about, you can smear on a thin layer of RTV near the coolant ports so that the gasket will seal a little better and help reduce the chance of a leak.. This is what I do when I have some pitting..

After a loooong time of not being able to work on the car, yesterday -finally- I managed to tighten the last screws and reinstalling the serpentine belt. I have not refilled/replaced fluids yet, but she's almost ready.

Putting together the things didn't take that long, but the heater pipe gave me problems to insert it again -of course-. I think the o'ring got damaged in the process... but we'll see.

In any case: when I was cleaning the mounting surface for the throttle body, I found an area around the water passages that was very brittle (guess how I found out?). The thin "lip" that holds the gasket from the wet side broke for maybe 1/2". Since it's on the wet side (under pressure) I'm not sure this would be critical, but there's some chance the gasket will not seal correctly. I applied some black silicone in the area as a precaution, but there's some chance I'll need to replace the plenum in the not-so-distant future :(

I'm starting a separate thread about that for clarity. I'll keep you posted :)

Well... I put some coolant and fired her up.
What I got:
- no dripping on the floor -absolutely amazing-
- a belt making ugly noises... or something running from the belt chirping
- white smoke coming out the tailpipe :confused:
- white smoke coming out from underneath the throttle body :mad:

I let the engine to warm up to working temperature, and made a brief tour including a short segment at 45 mph. Now the white smoke is gone, and the belt noise -whatever it was- is gone.

My guess is that coolant was being sucked through the throttle body from somewhere -probably the small part that broke-, and also dripping on top of the exhaust pipe underneath the throttle body. In any case, it looks like temperature stopped the leaks somehow (maybe it allowed the gaskets to conform better to the surfaces... who knows?).

I'm going to wait until the engine cools down and try to fire her up again. Hopefully the smoke and noise are gone for good.

Future viewers might like to know than this other thread
http://www.automotiveforums.com/vbulletin/showthread.php?t=969122
is a follow up to the present one.