Volvo penta MD22 complete overhaul

Posted on 07/05/10 02:20:11 by cyclonite

Untitled document The motor of our boat broke down and a few weeks till our vacation we needed to do something to get the thing working again.
As there was little time we decided to overhaul the engine ourselves.

After googling some information about the engine I came to realise this is about the worst engine ever built in history by perkins.
But the problem we encountered was yet not documented on the Internet.

The problem with the engine was water on the head of the engine, so at first we expected the head gasket to be the culprit.
We started by removing the head of the engine to look at the extend of the damage.

All valves were luckily undamaged but as this is a complete overhaul we adjusted the tolerances aswell.

Next to be removed was the oil and the carter.
The engine can be handled best when it is rolled on its back.
The carter can be removed quite easy then.

Motor head has been removed to realign the valves

The carter has been removed so we can extract the cylinders

You can see a little bit of rust already on the cylinders because the came in contact with water.

This shows the motor with its pistons

You can see the carter also contained water because of the rust.
This rust needed to be removed.

It is easy to spot the carter contained water because of the rust

Another problem: the starter engine broke because there was water on the engine head.

When starting there was so much torque, the aluminium broke.
I rejoined the broken pieces together and welded it back to one piece.

The startmotor broke, so this had to be repaired

You can see the weld clearly here.

Now it is reenforced

And now with the complete engine restored.

And once again it is a working part

After failing to find leaks in the head gasket we investigated further, next suspect was the heat exchanger.
Somehow this part leaked all its contents in the exhaust so we had to investigate what exactly failed.

This is why I took my axial grinder to open up the top of the heat exchanger.

(NOTE volvo penta thinks this part is worth 3250 euro's ex V.A.T. I personally think they are totally crazy to charge such amount for a piece is (badly designed) aluminium)

Now removing the labels of the culprit

Now grinding the top of the exchanger.

Grinding the top open for inspection

The inner cooling system is clearly visible now, the water is contained above the exhaust and intake tubes.

damn, no cracks to see in here!

After pouring some water in the exchanger the exact problem came to light.

You can clearly see the aluminium corroded ( you would expect a sea worthy engine to outlive more then 15 years) but because this part is so badly designed salt water can sit between the gasket and the heat exchanger.
and corrode the aluminium.

(I Really don't know why any sane person would design anything like this (any other then reducing the life expectancy of an engine!))

Ahhhh found it... after cleaning the exhaust I spotted a small hole

I tried to restore the aluminium with my tig welder but the aluminium is so polluted by corrosion I was unable to establish a good weld.

after some cleaning it became apparent the aluminium was to contaminated to weld properly

Next thing I did was just grinding off the flange to look at the extend of the corrosion, as you can see we now have clear shiny aluminium.

I remove the complete flange

This is the sawed of flange, as you can see it has holes where the leakage originated, this is aluminium which is designed in such a way this reduced the life expectancy of the engine.
Again this is to my knowledge completely unnecessary and only introduced by designers to have you buy parts when the aluminium is gone due to corrosion (extremely expensive parts 3250 euro's ex V.A.T.)

It is easy to see WHY the part failed, an enormous design flaw!