Exhaust manifold leak

[treilley]

We ran our first race of the season tonight. I have not run the results yet but it appears as though we placed second out of about 10 boats behind a Sabre 38,

When I first started the motor, Kathy smelled something burning. It was actually antifreeze. I checked the engine and there was a small amount of steam coming up from around the rear end of the manifold where it connects to the exhaust riser. It was also wet underneath that section. Is this common on a 20 year old M25? Does anyone know where the leak is likely coming from? I was pressed for time to make the start of the race so I did not have a chance to really get into finding the leak. We did motor for about 10 minutes with no problems in the cooling system.

 

[Loren Beach]

Corrosion takes it's toll

If this is your first mixing elbow replacement, your boat did better than our boat. When we bought our '88 model in 1994, the mechanic that did the engine survey pushed a screwdriver right through the nice-appearing paint on the elbow. The inside had corroded away with about 900 hours on the meter.
The seller was not pleased, but from my viewoint the whole engine survey paid for itself in that instant.

So, perhaps you need to do some.... poking around....
and get ready to replace that part soon. Unless it's the manifold -- after re-reading your description of the symptoms.

My .01 worth, with Wednesday discount.

Loren in PDX
1988 M25XP

 

[EGregerson]

leak

the burning smell might have been coolant on the exhaust manifold. Don't take too long to lock this down. You can always get home under sail, but you don't want to risk a cracked head or block. Hopefully it's just a loose hose connection, but.... they make stuff to spray on to help detect the source of the leak. good luck

 

[wurzner]

I'm with Loren...mixing elbow is where I'd start if I were you. Had to change one on my E32 with fwc A4 after I sold it to the new owner. He bought the part and I installed it for him since it is a pain in the @#$ to get to most of the time. The combination of hot exhaust gas and water, especially salt water does a nice job etching the metals away over time.

Good luck
shaun

 

[Shadowfax]

Yeah, it's the riser. Replaced mine 4 or 5 years ago. It's a stock part. If you have a mechanic you trust let them do it. The whole thing was under $500

 

[treilley]

PO indicated the riser was new. Surveyor agreed. It looks pretty new to me as does the iron pipe between it and the manifold. I will find out this weekend and let you guys know. Here are some photos from last season:

 

[Shadowfax]

I agree the riser looks new. I suspect that the problem is the iron nipple that connects the exhaust manifold to the riser. This should cost about $10.00 for the part. I'd still have your trusted mechanic do the job, unless you are a plumber or a talented shade tree mechanic.

 

[JMCronan]

From what you described the leak could be a bad seal between the OD tube and the maniford exit. When I replaced my riser, tubing and exit fitting I used a product called "ultra copper." A friend who rebuilds classic cars turned my onto this product. It can be purched at any automotive parts store. It is of tooth paste consistancy and when dry its a flexible, caulk like material. In cars engines it is used in high temp exhaust areas. Perfect for the exhaust riser. Works very well.
Also it could be the gasket was not replaced when your riser, OD tube and exit fitting were replaced.
Seems those would be the easiest solutions. Hope it turns out to be something simple.

 

[treilley]

It looks like the leak is coming from under the manifold flange gasket. I went out the the boat today and dried out the area and started the engine. Coolant started to ooze out from the bottom of the flange gasket. I tried tightening the bottom bolt but I only got about 1/2 turn and it still leaked. Ordered a new gasket from Hansen today and should be in by Tuesday. I will drain the system and replace the gasket using a little Copper Permatex to ensure a tight seal. Wait 24 hours and start the engine on Wed. when heading out for my weekly race.