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04-25-2016 10:13 AM
Re: Clogged Yanmar mixing elbow?

Hey Daniel.
That's a good theory. It's not possible to see the exhaust port when you take off the "elbow" pipe (or 45 degree pipe in my case). You can only see into the pipe you've just removed. The last time someone possibly looked at this was in the days before smart phones - with cameras - allowed you see around corners and make videos of out-of-the-way places in your engine. This is what I did to discover the ugly truth behind my fading engine!

Thanks for your comments!

04-25-2016 09:51 AM
Re: Clogged Yanmar mixing elbow?

Originally Posted by chrish0001 View Post
Hi Daniel,
In my case it was the exhaust manifold port that was completely blocked. The pipe connecting to it (with the coolant water inlet) was fine. I'm not sure why this was the case.

See photos (1) as it was when I first discovered it and (2) after cleaning out and refinishing the flange.


Wow! that's ugly.
Odd that the pipe was fine, but seeing that the manifold was blocked, maybe the pipe was installed while there was still an opening in the manifold and just not cleaned out by a previous owner.... Just "thinking out loud".

But really good that you fixed that. Could have caused much more problems.

Just shows that engine maintenance goes beyond changing oil and filters.

With all the work I did to my engine, I'm thinking a regular inspection of the head and cooling passages is a good idea too.
Good job, Chris!
04-25-2016 09:11 AM
Re: Clogged Yanmar mixing elbow?

Hi Daniel,
In my case it was the exhaust manifold port that was completely blocked. The pipe connecting to it (with the coolant water inlet) was fine. I'm not sure why this was the case.

See photos (1) as it was when I first discovered it and (2) after cleaning out and refinishing the flange.

04-25-2016 08:24 AM
Re: Clogged Yanmar mixing elbow?

I had a lot of carbon and rust buildup. I recently replaced mine as I think it was still original.

Did a top end rebuild of my 2GM while I was at it.

04-25-2016 08:07 AM
Re: Clogged Yanmar mixing elbow?

Hi All (even though it's 3 years since the last post!).
I have a Yanmar 3GMD and recently noticed a deterioration in engine performance. There was a lot of black smoke and occasionally, a black inky trail in the water. Eventually, it worsened to the point that, 2 weeks ago it would only idle.

It turned out that the outlet from the exhaust manifold was completely clogged to the point that I don't understand how the engine ran at all - let alone how the black smoke even made it out of the exhaust.

It wasn't just blocked with carbon - there was a hard rust formation which had, over time, almost completely clogged it.

I took off the manifold and cleared out the offending port and brought the part to a local machine shop to have the flange face refinished.

In my case the elbow isn't an elbow at all but just a short pipe with a flange which connects to the exhaust manifold block (with gasket in between).

Once all reassembled the engine ran like a dream. It had been slowly choked to death by an ever decreasing means of exhalation. From now on it's now on my list of things to check every 2 years.

BTW the engine is 32 years old and I suspect this had never been looked at previously!

12-06-2013 02:31 PM
Yanmar Mix Elbow

I started to see a lot of black/brown soot when revving by motor so it determined it could be 1 or 2 things:
  1. Injectors were becoming clogged and therefore needed to be pulled and cleaned or
  2. Exhaust elbow was clogged with soot.

At first I was not looking forward to pull the whole exhaust portion of the motor off, but it is super simple and can be done in about 15 min if easy access. Disconnect the cooling water hose from the mixing elbow and then disconnect the whole piece of the exhaust manifold (mixing and exhaust elbows) from the motor by removing the 4 bolts.

I took mine home, separated the exhaust elbow from the mixing elbow, removed as much scale as I could with flat head screw driver, then soaked the both pieces overnight in vinegar.

Thoroughly rinsed and check flow through each with a stream of water. Reassembled, put on a new exhaust gasket and then put everything back together.

Fired up motor and black/brown smoke was gone.

My elbow is original to the motor, 1992, but my motor only has 700 h.
12-06-2013 10:42 AM
Re: Clogged Yanmar mixing elbow?

now thats some smart thinking, fix your current stuff to act as working spares...kind of a sailors motto
12-06-2013 08:39 AM
Re: Clogged Yanmar mixing elbow?

Thanks for the tips everyone. I still plan on replacing the elbow because the welds look a little rusty and it is probably time anyway (2,500 hours). I'll clean up the old elbow and put it in the "spares" kit.
12-05-2013 12:35 PM
Re: Clogged Yanmar mixing elbow?

yup shops "boil them" if its cheap to do won there like here I would do that...however you can do the rest yourself using vinegar...
12-05-2013 12:29 PM
Re: Clogged Yanmar mixing elbow?

Seems cleaning would be a lot cheaper than replacing. I would pull it and if you see any carbon on it, take to a radiator shop and ask them to "boil it out." (not sure what the Portuguese term would be as they don't really boil it) They generally have baths of really strong chemicals that they can dip it into and it will clean it to bare metal. You should be good to go for several more years after that.
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