Yachting and Boating World forums: 1GM10 exhaust weld broken

I wrote this in reply to another thread, but think it may be worth it's own as it could save someone's engine

Here is where I am at...

My port 1GM10 has been getting progressively more difficult to start since around September last year. It has 472 hours and is 5 years old. I had been through the fuel system and had run out of ideas. I contacted Rob Walker, who over the telephone diagnosed the fault and is now a bit of a hero!

After speaking to the Engineer, Rob Walker at HMES Pwllheli he immediately suspected the exhaust, oh the Achilles heel of the 1GM10.

He suggested from what I had tried and the fact the engine felt like it had compression, though when I thought about this, my swmbo was the one who turned it over.. I forgot to take into account that she is a girlie. I can turn a 9hp diesel over just, I doubt she could.

So low compression. Rob suggested that the 1GM10 is renowned for taking a gulp from the exhaust when you shut down, if your levels are bad and no water lock fitted this can mean any water left sat in the down pipe gets sucked back up. I was confident that my installation should have meant this can't happen, steep down hill to the water lock and then up and out.

But..

If the exhaust elbow breaks, things are not so rosy. Inside the 1GM10 pipe is a sleeve to direct the water away from the manifold joint and thus the cylinder head.

Here is what I found.

As you see the sleeve which is meant to be welded to the manifold has broken away. Here is is alongside the down pipe.

Here we see the water inlet from the outlet of the anti-syphon valve. Note the proximity to the manifold, I found the sleeve inside the rubber pipe near to the water-lock. This meant water was pretty much gushing into the exhaust valve guide.

So I took the head off, and sure enough the exhaust valve was ruined (corroded), the pre-combustion chamber had rust all over it, the top of the cylinder was pitted with rust. Rob is now reworking the head, at least when it comes back from the shop, new guides and a good clean, new valves, new gaskets, exhaust to be welded.

Oh joy. Well, he thinks I may have it back by this weekend, so there is the silver lining.

I was surprised how easy the engine is to strip, this is a 5 year old motor, I am more used to this intensity with old high mileage cars, it was rather nice that bolts just undid without hassle.

Why am I writing this, well, if you start to have starting problems, or maybe even as part of routine maintenance, I would now suggest, inspect that weld on the exhaust, don't leave it like I did, it could mean a new head, mine has not corroded past the surface, but it could have done.

Hope this helps.