MDC11

[petersto]

Just bought a Centaur looking for help, one cylinder jacket/head warm the other hot. Decompressors altered while engine running show both cylinders working. Temperature guage showing normal. Also rev counter not working is it the guage or sensor, is it possible to check with a multimeter.

 

[VicS]

We've had cooling problems with a MD11C in a Berwick. It sounds as though one of the water passages in the exhaust manifold is nearly blocked. Water enters about half way along underneath the manifold an then flows via two fairly small passages to the cylinder heads. Clean out these and hopefully all will be well.

 

[petersto]

Thanks for that Vic I will bear it in mind. I bet the various bolts havent been out for a while.

 

[chrisD]

The rev counter on my MD11C packed up suddenly and its quite difficult to determine whether its the sensor or the gauge. First check all the wiring. The gauge itself should have a 12V supply as well as the supply to its light. Then the sensor should have two leads to the gauge, also to be checked.

Assuming all the wiring is OK, its a bit of a gamble which item to change. I was advised that a DC current should pass through the sensor from one terminal to the other (when its working the sensor puts out an induction AC which is decoded by the gauge). As I couldn't get a current through it, and it had a slight rattle when removed from the block (dead easy, just unscrew it) I replaced it and the problem was solved. The downside is the cost: £94 + VAT. Apparently the gauge costs even more.

 

[airbubble]

these engine series are prone to cooling channel blocks, especially after the winter lay-up when the deposits had the chance to dry and settle. Check it out, your head gasket of that cilinder will go sooner rather than later if it runs too warm.
There is also a small sort of bleeder /overflow channel in the cilinder head towards the exhaust manifold if i recall correctly, that is likely to be blocked. Can't recall exactly as it has been quite a few years ago when i used to work with these engines.
Rev counter sender /gauge issue has always been an impossible fault. The sender indeed gives a puls it picks up from the flywheel. The pulse rate should match the one for the gauge, there are different types that look alike. The number is imprinted in the side of the gaugehousing.
My normal first assumption was indeed that if the sender did not rattle and looked intact it was mostly the gauge, but i have been wrong there.

 

[drawp]

As VicS suggested, remove the exhaust manifold and clean out/flush through the circulating ports in the engine block. A good way to then clean the exhaust manifold waterways is to soak the manifold in an oxalic acid solution. Boots or any other chemist should be able to sell or order some oxalic acid powder for you.

 

[VicS]

The trouble with this is that in order for a chemical cleaning solution to work it has to come in contact with what it has to remove and if several cm. of narrow passage is blocked solid then it will take forever so the only way is with a piece of stiff wire perhaps followed by the acid. One of the two passages is fairly short and easy to unblock the other is longer and more difficult (this is the one more likely to be blocked).
I dont recall anything that may be what Airbubble is refering to but while the manifold is off a good look around would make sense. Sometimes its difficult to see where the holes should be when they get totally bunged up.

 

[drawp]

VicS. You're right about needing a good dig around in the water ports first with a piece of way. About 2 year ago I experienced problems with my MD11C not running at a consistent temperature. By clearing out the engine block and exhaust manifold with a piece of wire then soaking the manifold in oxalic acid solution, I cured the problem. It was surprising how much scale actually came out of the engine. The engine now runs at an even temperature.

 

[VicS]

Yes. Cleaning out the water channels in the blocks is a big problem. If all else fails I understand that it is possile to get the liners pressed out. The indication that the blocks are bunged up is a constanty rising and falling of the temperature although not going permanenty to a high reading.