Exhaust manifold leaking

[jlinder]

After some problems this season got the engine running but now I have a leak from the exhaust manifold. I guess it is time for replacement but I wanted to make sure I have all my ducks in a row before I start the job.

Specifics: 1988 OMC Cobra stern drive w/ 5.0L GM V-8 engine

1. A little unclear on the water path. From what I can see the water runs through the exhaust manifold then through a hose into the engine but I see only one hose. There is a place for a hose on the bottom of the manifold but that is capped off on both manifolds. What am I missing?

2. I guess I should check both sides and maybe replace both sides on the assumption that if one is bad both are worn out/rusted out. Right?

3. Any tricks or gotchas I should be aware of? I would hate to pull the manifold to learn that I am missing a part and have to wait until it comes. For example there is the rubber cap on the bottom of the manifold. Should this be replaced? What about a gasket kit for the elbow? Any gaskets I don't know about, etc.

4. Again, what about tricks or tips? Any tips to make it easier or "whatever you do make sure to...." notes?

Thanks

BTW - it took a while but I found the manifold here at iboats. Good price it appears. Love to support those who provide this forum.

 

[Bondo]

Re: Exhaust manifold leaking

1. A little unclear on the water path. From what I can see the water runs through the exhaust manifold then through a hose into the engine but I see only one hose. There is a place for a hose on the bottom of the manifold but that is capped off on both manifolds. What am I missing?

Ayuh,... The water flows From the motor to the manifolds, into the risers,+ Out with the exhaust flow...
Yes,.. Replace them as a Pair...

 

[Gary H NC]

Re: Exhaust manifold leaking

Best bet is the whole kit...new risers,manifolds,gaskets and all the mounting hardware...
I just put a set of these on a 5.7 Merc and they looked to be very well made kits....had the nice thick gaskets too..

http://bpi.ebasicpower.com/mm5/merc...Store_Code=ebasicpower&Product_Code=HGESBCOMC

 

[jlinder]

Re: Exhaust manifold leaking

Nice kit but unfortunately they only have it for the center riser model. Mine has the riser at the rear and is called the log type.

Thanks

 

[littlebookworm]

Re: Exhaust manifold leaking

You can get a kit to replace the log style with a center riser style exhaust syste, I did that with my 1980 5.7 engine. Straight forward project. Much better cooling than the log style setup. Since you need to replace the manifolds, risers, and hoses anyway, you're better off with the conversion. Hardest part is getting off the old manifolds; the bolts are usually rusted and the manifolds are heavy. Use alot of KD Blaster. One trick in removal and installation is to use one long bolt with the head cut off as an alignment tool/manifold holder as you work on the other bolts. Check previous posts for more details. Good luck. Hy

 

[jlinder]

Re: Exhaust manifold leaking

I will have to look for the conversion kit. Any idea on wher to get it?

I have pulled the risers last year and they looked pretty good. Do they tend to wear out along with the manifolds (around the same time)?

I was thinking that the water sits in the manifold for long times but drains out of the riser fairly quickly.

Thanks for the tip with the long bolts. Would hate to try to align and put bolts on at the same time.

What about KD Blaster? Is that the best you have found for breaking nuts free? Does it help to spray it on and let it sit?

 

[P 0 P E Y E]

Re: Exhaust manifold leaking.....but where and are you sure?

Re: Exhaust manifold leaking.....but where and are you sure?

You said the manifold was leaking. Are these the original manifolds?

I missed the sentence that describes where it is leaking.

I also seem to have missed the sentence that describes how you came to the hypothesis.

Sorry, I am almost 50 and it's close to my bed time.

 

[jlinder]

Re: Exhaust manifold leaking.....but where and are you sure?

Re: Exhaust manifold leaking.....but where and are you sure?

You said the manifold was leaking. Are these the original manifolds?
I missed the sentence that describes where it is leaking.
I also seem to have missed the sentence that describes how you came to the hypothesis.
Sorry, I am almost 50 and it's close to my bed time.

Almost 50? That makes you a youngster.

Water is coming out around the bottom of the manifold. Could not find a definite spot where it is leaking but can't see where else it could be leaking. There is too much do be able to know exactly where it is leaking.

What is the water flow? Does the manifold pump water into the block or does it only go through the manifold to cool it? I ask because if it goes through the block it could be a leak at the manifold gasket. If so that would be a much cheaper (I hope) fix.

Are they original - don't know. Could be.

Happy fathers day

 

[Bondo]

Re: Exhaust manifold leaking.....but where and are you sure?

Re: Exhaust manifold leaking.....but where and are you sure?

What is the water flow? Does the manifold pump water into the block or does it only go through the manifold to cool it?

Jeez,... What am I,..?? Chopped liver,..?? I answered that in post #2.....

Water is coming out around the bottom of the manifold. Could not find a definite spot where it is leaking but can't see where else it could be leaking.

Now it sounds like it Froze,+ Split either the Manifold, or the Block, or Both.....

 

[jlinder]

Re: Exhaust manifold leaking.....but where and are you sure?

Re: Exhaust manifold leaking.....but where and are you sure?

Jeez,... What am I,..?? Chopped liver,..?? I answered that in post #2.....


Now it sounds like it Froze,+ Split either the Manifold, or the Block, or Both.....

Bond-O - Now it's my senior moment - you did answer it.

Could residual water have remained in the manifold/engine and frozen causing it to crack?

I always winterize, remove the little drain plugs, etc. but I wonder if residual water can remain and cause a problem. Is there something I miss when I winterize?

What about the manifold to block seal? Do the gaskets form problems often? I did notice that the water leak got less as the engine warmed up and I searched for the problem.

 

[Bondo]

Re: Exhaust manifold leaking.....but where and are you sure?

Re: Exhaust manifold leaking.....but where and are you sure?

What about the manifold to block seal?

Ayuh,... Only exhaust gases pass there....That's Not the problem....

You've got to run it so it's leaking,+ then LOOK to see Exactly where it's leaking....

 

[jlinder]

Re: Exhaust manifold leaking

I tried but it seems to come from no specific point, just water dripping off the bottom and wet everywhere. Could not find any thing specific.

Guessing my best first move is to pull the manifold and start looking, or is there a better suggestion to finding this

 

[jlinder]

Re: Exhaust manifold leaking

Sorry this is becoming a long thread but went out today to work on it. Ran it up to temp and water leak almost gone.

Let cool down and until the engine was stone cold (outside temp) and started up again and still almost no drip.

Starting to think it is a problem with the gasket seal to the exhaust manifold. The leak opened up over the winter as the engine sat.

Could I be right?
How common is this?
If I am right sounds like replacing the gaskets would be a solution (check the manifolds while I have them off of course)

Thanks to everyone who has stuck with this thread. It really helps.

 

[MERCrazy]

Re: Exhaust manifold leaking

is it that difficult to post a picture????

PICTURES TELL A THOUSAND WORDS ! MAKE that A sticky !

 

[P 0 P E Y E]

Re: Exhaust manifold leaking

Many manifolds have a drain plug, is yours tight? The plug will be a pipe plug toward the back or lowest point.

Mechanics use this plug to drain water out of the manifold at winterizing time.
It sometimes may be left hand tight. It is also subject to corrosion.

(LOL @ Chopped Liver)

Check your hoses for lose or bad clamps.

Good luck and stay with it.

 

[jlinder]

Re: Exhaust manifold leaking

There are drain plugs in the block I always remove and the manifolds have what looks like ait could be a stub on the bottom that you could connect a hose to but that is capped off with a rubber cover that is clamped on.

I checked the rubber cover but water is not coming from there.

I could grab a picture but it would not show anything. The water appears on the bottom and I can't see anything (need a mirror to see it).

Still really confused about how it healed itself.

 

[Bt Doctur]

Re: Exhaust manifold leaking

It`s beginning to rust itself shut. PULL THE MANIFOLD OFF AND LOOK FOR CRACKS.

 

[jlinder]

Re: Exhaust manifold leaking

There are drain plugs in the block I always remove and the manifolds have what looks like ait could be a stub on the bottom that you could connect a hose to but that is capped off with a rubber cover that is clamped on.

I checked the rubber cover but water is not coming from there.

I could grab a picture but it would not show anything. The water appears on the bottom and I can't see anything (need a mirror to see it).

Still really confused about how it healed itself.