4.3 merc water in #5 cylinder

[Clarko1988]

Took heads off to check gaskets and for cracks cant seem to find anything this motor was rebuilt last summer including heads i overheated once and instantly shut the motor down.

 

[Scott Danforth]

Look at the manifolds

 

[Clarko1988]

Look at the manifolds

Can it leak in just one cylinder?

 

[achris]

Can it leak in just one cylinder?

@Scott Danforth is referring to the exhaust manifolds, and yes....

 

[Lou C]

In the pix it’s hard to say where the water could be coming in but when I had the same problem it was the 2 front cyls, #s 1&2. The Head gaskets looked ok when I took the heads off but when I removed the gaskets the fire rings on those cyls were slit around the circumference. My thought was this was letting water in after running as it cooled off. The thing that looks suspicious is the intake gasket, that water port on the left rear side looks like it may have been leaking but that would put water into the cam valley & motor oil.
If you have the older style wet joint exhaust (before 2002) the gasket between the manifold & elbow is a likely cause, not so much with the later wet joint system. Look inside the exhaust ports of the manifolds for clues.

 

[Bondo]

Can it leak in just one cylinder?

Ayuh,..... If the manifold/ riser joint gasket fails, in leaks into the downhill cylinder,......

 

[j cat]

Took heads off to check gaskets and for cracks cant seem to find anything this motor was rebuilt last summer including heads i overheated once and instantly shut the motor down.

engine over heats and many have the head gasket damage ... looks like engine water ports dirty ..

 

[Clarko1988]

engine over heats and many have the head gasket damage ... looks like engine water ports dirty ..

Ive check head gasket and didint see any thing no cracked nothing

 

[achris]

Ive check head gasket and didint see any thing no cracked nothing

I agree. For the photos it looks more like an exhaust manifold water intrusion... Seen it many many times unfortunately..

Chris...

 

[Clarko1988]

Not sure this is my problem but how would i find out if this is cracked? There was no water in the other cylinder just number 5.

 

[Clarko1988]

Not sure this is my problem but how would i find out if this is cracked? There was no water in the other cylinder just number 5.
View attachment 358690

I made a mistake it is cylinder 6 that has the water

 

[Lou C]

#6 is the rear one on the starboard (drivers) side.
do you have wet joint or dry joint exhaust?
if wet joint what do the sealing surfaces of the manifolds/elbows look like?
salt or fresh water?
the best thing to do would have been to air pressure test the cooling system passages before removing the cyl heads.
that and taking the manifolds & elbows apart, and propping up the manifolds level and filling (careful flammable) with acetone. Acetone has less surface tension than water and will find leaks in a manifold that won't show with water till it warms up
when I had water in a cyl I first tested my old manifolds (both passed) then rigged up a way to test the head gaskets with the engine running. What I found was that exhaust gas was getting in to the cooling water. That confirmed either a blown HG or cracked head. Dis-assembly revealed both.
But I ruled out the manifolds first.
Where u are at now, you can:
test the manifolds
take the heads off to get magnafluxed and gone over at a machine shop
check the deck of the block very carefully
report back what you find.

 

[Clarko1988]

Things i have done so far. Cleaned/filled exhaust manifold with acetone did not detect a leak. Also when i installed riser gaskets i never used a sealant like i should have. I have checked over heads with small mirror and the exhaust port and did not see any cracks or anything.

 

[QBhoy]

let her sit for a while after she has had a supply of water to her and ran...then take the plugs out and watch for water coming out number 6. odds on that the water is from the manifold or riser, you would think.

 

[Clarko1988]

So installed new head gaskets. Followed book by a T still not sure how to test my exhaust manifolds and risers. Also is it possible that intake manifold leaks into only cylinder number 6?

 

[Clarko1988]

#6 is the rear one on the starboard (drivers) side.
do you have wet joint or dry joint exhaust?
if wet joint what do the sealing surfaces of the manifolds/elbows look like?
salt or fresh water?
the best thing to do would have been to air pressure test the cooling system passages before removing the cyl heads.
that and taking the manifolds & elbows apart, and propping up the manifolds level and filling (careful flammable) with acetone. Acetone has less surface tension than water and will find leaks in a manifold that won't show with water till it warms up
when I had water in a cyl I first tested my old manifolds (both passed) then rigged up a way to test the head gaskets with the engine running. What I found was that exhaust gas was getting in to the cooling water. That confirmed either a blown HG or cracked head. Dis-assembly revealed both.
But I ruled out the manifolds first.
Where u are at now, you can:
test the manifolds
take the heads off to get magnafluxed and gone over at a machine shop
check the deck of the block very carefully
report back what you find.

Had the heads tested and the checked out fine. Did the head gaskets today. Still trying to figure it out. Is it possible that intake manifold leaks just in cylinder 5?

 

[Lou C]

Go back to your pic of the engine with the intake removed. As I pointed out earlier there is suspicious rust deposits on the cyl head near the intake port for that rear cyl and the rear water passage in the cyl head. The intake gaskets on the Vortec engines were more failure prone than the Pre Vortec probably due to some poor quality gaskets and confusion about proper torque specs. The torque spec for the Vortec is like 1/2 of the Pre Vortec. If the mechanic is not aware of this you will have leaks. On the Pre Vortec the intake gaskets rarely if ever leak. Honestly I think the old style was a better design; 12 bolts instead of 8.

 

[dubs283]

....The torque spec for the Vortec is like 1/2 of the Pre Vortec. If the mechanic is not aware of this you will have leaks. On the Pre Vortec the intake gaskets rarely if ever leak.....

Even less than half, is around 12 lb/ft iirc. With a proper sequence and multiple passes with slightly increasing torque. Also, even though not recommended I use a gasket sealant around the water passages on both the heads and intake manifold

 

[Lou C]

The sealant is a good idea if either the cyl head or the manifold is pitted on the sealing surfaces. I recall when the Vortec engines were introduced on both the V8s and V6s in GM vehicles there were a LOT of failures resulting in antifreeze getting into the cam valley & motor oil. Eventually the gaskets were changed & improved but I think eliminating 4 bolts (2 on each side) was a mistake. With the pre Vortec engines intake gasket failures were very rare.

 

[Clarko1988]

Well i clean it up well and installed gaskets yesterday before seeing this reply but i did not use any sealer just on the ends of manifold. I torqued doen to 12