Work starting on my MD11C this weekend - nervous

S

Swanrad2

Well-Known Member
Joined
16 Aug 2005
Messages
974
Location
Cheshire
Visit site
Three years ago my Centaur started overheating above 3000 revs with lots of steam in the exhaust and very little water. Replaced the impeller etc without effect, the natural conclusion I think is Head Gasket. The boat was pulled out of the water and work (land based) got in the way, but, I am starting this weekend to renovate the engine starting with the gasket. I was also thinking of adding one of the new fangled water filter traps with the transparent top and widening the intake from the current feeble effort. All of this assuming the thing isn't damaged enough to form my next mooring sinker instead.

Firstly any suggestions for what else would be a sensible addition/improvement to the EXISTING engine as I quite like not spending £5k on a new engine? Secondly are there any other obvious culprits for the fault (it was a suddenly developed fault after overheating when an impeller failed so, although the water ways aren't great they are unlikely to of caused the problem).

Cheer

Tony
 
The fact that you have already observed a lack of water flow points to blocked galleries. Don't take things to bits until it's necessary. Flush it first. A weak solution of patio cleaner may work, or I'm sure the chemists in the audience will have alternatives.
 
Sounds like head gasket to me, you could always try a liquid gasket repair product as an alternative. I've just used "Seal-Up" by CarGo (find it on Amazon) to repair blown head gasket on the car and so far so good! Also plenty of vids on u-tube for head gasket fails and repair solutions.
Good luck
 
Swanrad2 said:
Three years ago my Centaur started overheating above 3000 revs with lots of steam in the exhaust and very little water. Replaced the impeller etc without effect, the natural conclusion I think is Head Gasket.
Click to expand...

This doesn't make a lot of sense. It overheated, there wasn't much water coming out of the exhaust, so you assume it's a head gasket problem? Why??
 
I did complete rebuild of the earlier MD2B (very similar engine to MD1C) and I found that when I removed the heads, I could see that the water jackets were cruded up. I poked about with welding rods and screwdrivers and loosened the rust but not easy to get out.

Once I removed the blocks from the crankcase, the task was very much easier. However, if you have to remove the blocks you will need to take some careful measurements prior to rebuild to set up the compression.

If you remove the blocks, you will need to measure with a micrometer, the thickness of the crankcase shim/gasket.

Going back your question about making an improvement, you could look at a closed loop system using a heat exchanger from Bowman but you will need to find some form of fresh water circulator. I had thought about this and looked at using a central heating pump and a 300W invertors but did not take it any further.
 
Last edited:
You may well have blocked passageways in either the heads or block . The drilled passages in the block appear when the heads are removed. There will be lots of rust as well as other things and mechanical cleaning may succeed where brick cleaner fails

A lot of the crud can be removed by taking off the drain cocks and then clearing the passageways while squirting water into the various passageways.

You may have to examine the gasket face on the block carefully to find some passageways if completely blocked but do no go random drilling unless
absolutely sure is is a genuine passage you are working on. Also clean the cooling passages in the exhaust manifold.

You should take the opportunity of servicing the head while it is off and I do not mean a boy racer job grinding the valves into the seats. These diesels
have a differential angle between the valve and seat and this can be lost by excessive grinding in. Take the head to somewhere who has the machinery to
do a proper job and preferably a company without "marine" in the title as they can grind the valves and do the seats to the correct angles at a reasonable price.

There are some machine shops which cater for motor cycles of uncertain age and usually these charge a realistic price. Check your Yellow Pages.
 
Swanrad2 said:
Three years ago my Centaur started overheating above 3000 revs with lots of steam in the exhaust and very little water. Replaced the impeller etc without effect, the natural conclusion I think is Head Gasket. The boat was pulled out of the water and work (land based) got in the way, but, I am starting this weekend to renovate the engine starting with the gasket. I was also thinking of adding one of the new fangled water filter traps with the transparent top and widening the intake from the current feeble effort. All of this assuming the thing isn't damaged enough to form my next mooring sinker instead.

Firstly any suggestions for what else would be a sensible addition/improvement to the EXISTING engine as I quite like not spending £5k on a new engine? Secondly are there any other obvious culprits for the fault (it was a suddenly developed fault after overheating when an impeller failed so, although the water ways aren't great they are unlikely to of caused the problem).

Cheer

Tony
Click to expand...

Injection point into the exhaust first thing to look at if low flow despite new impeller.

If overall flow is good but overheat check thermostat

but if that's Ok

The water passages in the exhaust manifold from the T piece ( inlet) on the underside to each of the heads is the next thing to look at.

Blocks get their water jackets crudded up too .


Check availability and prices of parts before tearing into it.........do easy and inexpensive things first


Workshop manual if needed on Bluemoment
 
The water circulation wasn't great anyway, I had the exhaust elbow off to help - it did. We had to run the engine for 5 minutes with very little or no water circulating and overheated it for the sake of safety, replacing the impeller soon after. After this event the amount of water decreased and when at temperature and higher than 3000 revs this turned to steam - I thought head gasket most likely under those circumstances.

The process I am contemplating is therefore take the head off and clean up where possible and replace the gaskets (mechanic friend willing to work for beer makes this doable). The boat has been sitting for nearly four years now so a coupe of bits need freeing off and cleaning up, do this. Service the engine. Start it and run acidic central heating solution through it for a few hours.

I am the definition of 'not an expert' but this seemed like a sensible order to work in?
 
sailorman said:
Brick cleaner
Click to expand...

Billjratt said:
The fact that you have already observed a lack of water flow points to blocked galleries. Don't take things to bits until it's necessary. Flush it first. A weak solution of patio cleaner may work, or I'm sure the chemists in the audience will have alternatives.
Click to expand...

I'd try to avoid strong acid ....... My preference would be for weaker acids. Sulphamic acid perhaps or weak organic acids such as citric acid.

Trouble with trying to acid clean anyway is that if its blocked the acid doesn't get to where its needed.
 
My MD11C won't do 3000 revs, the max in the handbook is 2500 and I don't take it there either.

I had a problem with overheating earlier this year and found a worn impeller with one missing lobe.

Replacing the impeller helped but I still have problems @ 2200 rpm so I run at 2000 rpm which it will do for hours.

My exhaust injection point is clear, checked that for zero cost.

I have replaced the thermostat which was failed open (£50), but have been running without all season at 2000rpm or less.

The next thing is to try flushing the block with oxalic acid solution but if there are blocked passages it won't find it's way to where it's needed. I have had some oxalic acid in the exhaust manifold via the temp sender but I wasn't satisfied that it did much, I did see some bubbling which could have been CO2 but it could have been air.

Be carefull with the cooling water gallery drain plugs, I managed to break one off when draining the engine down to winterise it the first year I had it. I can open the other two and clear water comes out, not fast but there is a way through.

I suggest that you try much harder to solve your overheating problems without dismantiling your engine, but I would say that because it's what I'm doing.

If you want to swap notes or chat about it drop me a message.
 
Tam Lin said:
PM sent - reason - don't want to bore everyone else again!
Click to expand...

Now that's the mark of a gentleman!

As you have the opportunity to get cheap, skilled labour I'd go for a cylinder head service, even if it doesn't cure the problem, it's another job done and out the way. It is also an opportunity to view the cooling jacket waterways and maybe get some of the more difficult crud dug out. Unless you know that you recovered all the failed impeller, then a lost vane may be blocking the system. With the advantage of having cleared some of the crud out manually during the cyl hd service, a soak in your choice of acid and reverse flushing with as much pressure as you can achieve should push any significant bits out. Don't flush until the head is back on or you'll have fountains gushing forth - perhaps obvious, but worth a mention.

Best of luck,
Rob.
 
Swanrad2 said:
Three years ago my Centaur started overheating above 3000 revs with lots of steam in the exhaust and very little water.
Tony
Click to expand...

3,000 rpm !!!???? I don't rev my MD11C more than 2,000 rpm and this is if I am in a hurry. This may be the reason why is overheating. Raw water engines will eventually have their water jackets reduced due to accumulation of salts and rust, therefore they will overheat easier.
 
CAPTAIN FANTASTIC said:
3,000 rpm !!!???? I don't rev my MD11C more than 2,000 rpm and this is if I am in a hurry. This may be the reason why is overheating. Raw water engines will eventually have their water jackets reduced due to accumulation of salts and rust, therefore they will overheat easier.
Click to expand...
As I recall the md11C was 24-2500 and the 11D was increased to 3000 and labeled as 3000 series
The cyl base shims are metal and reusable with the same pistons so if removing blocks take note!
 
You must log in or register to reply here.

Share this page

Top