Has anyone come across this problem where the coolant is leaking from the exhaust manifold gasket ? 96 4.3 V-8 200,000 miles - reversed cooled cylinder heads. At 170,000 miles I performed a complete tune-up. New distributor cap and rotor, spark plugs and wires. So 30,000 miles later, it started out with rough idle but would run fine under a load. The rough idle turned into a multiple engine misfire according to the OBD II scanner. I checked all spark plugs for fire and they all checked good. After erasing the codes the check engine light would come back on and the scanner said that cylinder #1 has a misfire. I pulled #1 spark plug and it was shinny clean compared to the other plugs. I performed a compression test on all cylinders , #1 cylinder 150psi , #3 cylinder 145 psi . All cylinders checked out with in 10% of each other. I pulled the dipstick no water, looked under oil fill cap and it's clean. No white smoke from the exhaust pipe. After scratching my head for a couple of days I noticed some water on the exhaust manifold at the#1 cylinder. I wiped it off and started the engine which was cold and there it was, within 10 seconds small drops of water would leak out of the exhaust manifold gasket. So I know that either the head is cracked or the head gasket has failed. Can someone explain why compression is still good at #1 cylinder? Are these heads known to crack ? I've owned the car for the last 15 years and has never run hot or over heated. I'm the only driver. Thanks for reading this !! ( Tried to load a picture but I'm doing something wrong. ) Where else on this site can I post my question ?

 

May be a direct leak from water jacket to exhaust port,
which is not "in the hole" for a compression check to
"see".

Or from water jacket to intake port, which would
"steam clean" the plug, and blow high water vapor
out to the exhaust.

The GM V6es are pretty reliable but "stuff happens".
Casting flaw or overheating episode, loose intake gasket,
etc.

Might look at whether the 4.3 is using a "wet" intake
in this model year, or has moved to a "dry" intake that
doesn't see water at all (like the LSx generations).
Could give the intake manifold bolts a "snug-up"
just for luck if the intake has coolant running through it.

 

Thanks for your help Jimmy blue - the intake is dry and is off the engine. I'll pull the head one of these days I've been busy with other projects. Yeah that makes sense on the compression test , a tiny crack in the water jacket your right. I'll post the official diagnosis when I get the head checked out !!

 

There are so many ways to test for a blown head gasket on your 4.3L, 5.0L, 5.7L GM van (or mini-van, pick up, SUV) that it can get confusing. Well, I'm going to show you three different ways to test for a blown head gasket. These are step-by-step tests that will help you to get to the bottom of the problem.

 

Thanks for your help Chevyboy@22 but the 3 steps didn't come through on your reply ! So to get the head ( pressure test and magnafluxed ) is $200. A rebuilt head from Clearwater FL is $225 .l wish I could have found out if the head was cracked. The head gasket had some erroded areas around cylinder one . My gut tells me that the head was cracked. But yeah I would like to read your 3 steps when it comes through - Thanks for your time !!

 

Your welcome!

 

Question is (if it's cracked at all) "from where to where?".
You can have crack from cylinder to water jacket,
cylinder to intake port, cylinder to exhaust port, water
jacket to either port and so on - at least 4 "domains"
which could communicate in any permutation. Leaving
aside the oil return, since oil is not the problem under
consideration.

Cylinder-to can use a leakdown test with a spark plug
hole adaptor to air fitting (common auto parts store tool),
or you can make your own with a spark plug anti-fouling
adaptor, an air connector and suitable bushing between).
A proper leakdown tester will include a check valve
and pressure gauge, but you can shade-tree it.

Pressurize the hole (bearing in mind the engine may
make an abrupt turn up to 1/2 revolution, watch the
fingers) and watch for coolant activity at the radiator
cap, listen to the oil fill hole, intake and exhaust ports.
Leakdown-rate match between cylinders will say if
you've got one hole different than the rest, which
is your pony.

Pressurize radiator to see if there's coolant weeping
to intake or cylinder, whether it ends up in the runner
or in the hole. Since you mentioned steam cleaned plug
this is where I'd start. You could put a "T" in the heater
hose easily, be sure not to start with full compressor
air pressure as this is likely to explode a 50-year-old
brass radiator or heater core. Maybe 10PSI (or
whatever barely doesn't crack the radiator cap pressure
relief).

 

Jimmyblue - thanks for the info and I will definitely refer back to this on the next time I trouble shoot a cylinder head problem. So I wish I could have found out exactly whether the head was cracked or not but getting it magnafluxed and pressure tested was almost the same money as a rebuilt cylinder head. Thanks again and I appreciate your help !!