Oil from Raw Water Exhaust 2GM20C

[sailorchic34]

Originally Posted by Lambada30

Hi all,

Thanks very much. Is it hard to replace the head gasket? Is there any damage I can do by trying to do this?

Someone at the club suggested that if it was the head gasket the engine shouldn’t be able to start... or would be hard to start. However, mine starts fine... is this right?

As to starting, it depends. Many times a blown head gasket does not lower compression fast enough to cause hard starting. So easy starting, with no or little blowby (with oil fill off. Trust me if it's high blow by you will know pretty much instantly.

As to ease of replacement, Even some blondes can replace head gaskets. While the head is off, check that valves set well and head is flat (machinists level and feeler gauge). clean the block and head completely, really clean, add a drop or two of oil to each head bolt/nut, install the head gasket, correct side up (will be a mark on the head gasket), install the head with hand tight bolts at first.

Then starting from middle and working to the outsides equally and in a x alternating pattern start tightening the bolts. I do it in 25ft lb segments to 50 ft lbs then 14# and a final 10# to 74 ft lb (if memory serves). Slow and smooth is pro. A good torque wench is a must. Then reinstall the rocker arms / push rods and adjust valves to .008 inch (Again with my memory of it).

Assuming head and block is flat a head gasket and torque wrench should be $200 ish total. The Head bolts can be reused. Newer engines have single use head bolts, but the Yanmar Gm's are old school all the way.

[Cheechako]

I'll third that a head gasket my be the problem.
.. and what SailorChic said, sometimes hard starting, but often not.
It's even possible the head bolts need retightened. But a new head gasket on that little engine shouldn't be too hard to do.
Check out on line videos:

https://www.youtube.com/watch?v=qp056LYvdRc

[Bleemus]

I think sailorchic nailed it. Buy a good torque wrench and pull the head.

[Lambada30]

So We’ve started removing the head. Once we got down to the head bolts we found that they were incredibly tight. Unfortunately the final bolt to come out sheared leaving about 5cm of bolt in the block however the head should still come off around the broken bolt shaft. Despite this we can’t get the head off. We’ve tried putting oil in through the injectors and turning the engine over but compression is escaping somewhere and therefore won’t push the head off. Any ideas how to separate the head?

I guess I’ll also need to remove the sheared bolt once the head is off. Any ideas on the best way to do this?

[sailah]

So you sheared a bolt head off but you still have the stud sticking up (assuming the head comes off)? You are likely dealing with corrosion down in the threads so go find the best thread penetrant you can find. I love Kroil but not sure it's available in Australia. Some people swear by acetone and ATF fluid mixed 50/50.

Then I'd torch the bolt shaft to get it hot, but not red hot. Hot enough to get some serious heat down in those threads. When I see oil smoking off I know it's hot enough. Then get some of your penetrant out while things are hot and soak where it goes into block. Personally I'd do this 4-5 cycles after letting it completely cool. Over a week if you have the time. Soaking it in penetrant every time you walk by.

Then get a pipe wrench and grab onto what is left of shaft. Try "tightening" the bolt every so slightly. Then try to loosen.

It's hard for me to "feel" the bolt from across the planet but if I felt it really was in there, sometimes torque isn't the answer and can make things a LOT worse like if you shear it off flush with the block.

So I may opt to weld a nut on top of the stud and make it a bolt again. Then I'd put my 18V 1/2" Makita impact gun on there and let it rattle away. Often those shocks are what breaks up the rust bond and it's very little sustained torque that breaks things.

A bolt sheared off flush with the block is a pain to deal with, and the repair options get limited and expensive at that point. Try to preserve the stud sticking up at all costs and don't just go reefing on the shaft with a pair of pliers unless you feel lucky.

As far as the head not coming off, doubly and triply check that you have all the bolts out. Consult the service manual. Then do it again. Someone I know was prying on their Westerbeke head and it wasn't coming off after they swore they had removed all bolts. Except they hadn't.

But assuming you have, there are typically pry spots between head and block for this purpose. Don't pry on expensive bits, find solid cast iron and get a good pry bar in there. Also dead blow hammers work well to tap things and won't break things.

[Lambada30]

Hello everyone,

Thought I'd give you an update on the adventure.

Our assumption that the cylinder head would pop off over the broken bolt should have been correct. However, there was far more to the story. The head bolt was virtually chemically welded to the head and block which is why the head wouldn't lift off.

After a day of using wedges, hammers and crowbars to see if we could shear the bolt between the head and block, we drilled the centre of the bolt out of the head. This weakened the bolt (probably the direct heat) enough that we could get a crowbar into part of the head and twist the head around until the bolt sheared off.

With the head off we could see why the bolt had stuck so hard - we are talking REALLY STUCK! We tried removing some left over bolt (just some stuck to the left hand side of the bolt hole) from the head with a chisel and hammer and it still wouldn't move. It turns out that the exhaust outlet on the head had a hole that led into the cylinder head bolt hole. A previous owner had put some sort of exhaust putty into the head to patch it up. This in turn found its way into the cylinder bolt hole and chemically welded everything together! By the way the head was a mess. 85% of all water cooling jackets were blocked, the second cylinder had no access to the exhaust outlet and there was clear head gasket blow by.

A friend reconditioned the head and did an amazing job!

We then had to remove the remaining bolt from the block. After drilling a hole through the bolt we put an ezy out on it. Unfortunately the ezy out snapped off in the hole. Well 5 hours with a dremel and an helicoil later, we are ready to reassemble! Fingers crossed that the original problem is fixed. I'll upload some photos.

[Lambada30]

Here are some photos.

[Cheechako]

You are tenacious! Great job!
Boatwork 101: "Whatever you thought you could do in 3 hours will be at least 3 days, and discover 3 other things to do to complete the task!"

[NorthCoastJoe]

That sounds like a brutal job. Don't forget to clean the block too, check your freeze plugs for corrosion. Good luck should be fine when you are done.