Volvo MD7B

[Cotillion]

Take delivery of boat and all seems well.

Chugged out of harbour en route for home port and approx 2M out I go below for a brew. 'Engine smells hot' thinks I when suddenly without any warnings going off, engine dies.

Open the cover to be greeted by a small amount of smoke and notice oil trickling out from under the filler cap. Sail back to port and drop the hook. Manage to restart the engine but she wont tick over. Inspection reveals a decent quantity of water in the fuel filters. Call engineer who pumps out tank and bleeds system. Once again engine starts but wont tick over and the engine still smokes and oil still leaks from filler cap.

Engineer says there is back pressure from the exhaust and offers an opinion as to what might need to be done and I am now in deep depresion and cannot think straight.

This morning I have given myself an asre kicking and got my brain back into gear and whilst I am no expert by a long way, I have come up with what I think is a plausable reason for my troubles, which is different from what the engineer is telling me.

What might yours be please?

Kim

 

[spottydog]

Same thing happened to me when I bought my present boat. The engine was a Volvo MD6A. After the initial panic I sussed the thermostat wasn't opening, removed it and carried on to home port with no further trouble.

 

[VicS]

In fairly general terms because I have no specific info on that engine. (well there is a w/shop manual for the MD7A on Bluemoment)

If the engineer says there is back pressure from the exhaust then check on the water-cooled exhaust bend for restrictions and on all the hoses for internal collapses. He might not be right but it is silly to ignore the advice of the professional expert and since it does not involve great expense to check out would be sensible to do.

The oil leakage from the filler cap suggest that the crankcase might be pressurising so check on the breathing, but I think that's just a hose from the rocker cover to the air intake silencer. Does the filler cap not have seal on it? Maybe this is not a significant observation.

Engine smoking suggests a problem with the injectors at least if its black smoke. I wonder if there is any connection with the water in fuel problem which may have been what stopped the engine in the first place. I think you have got to look very carefully at the fuel system from tank to injectors.

I think you can ignore the thermostat until you have the engine running properly. It wont have any effect until the engine gets up to working temperature. It'll be closed anyway. Do check that you have a good flow of water out of the exhaust nevertheless.
It is of course possible that the engine did overheat due to lack of coolant be that due to a restriction anywhere from inlet to exhaust bend, worn pump impeller or faulty thermostat. That may have caused some serious damage, expensive to rectify if that was what stopped the engine. Hopefully not.

Best of luck. Keep us informed.

 

[Cotillion]

Thanks Vic

My thoughts were a sticky exhaust valve. The engineer thinks perhaps head gasket or piston rings. As I said, I'm no expert but I dont see a link between exhaust back pressure and the head gasket. There is plenty of water coming out the exhaust. The smoke in the engine compartment was, I'm fairly sure, exhaust smoke. Give the engine some revs and it seem fine but cuts out on tickover.

The engineer's first thoughts were that the engine is knackered and will need rebuilding. He's having the head off on Monday so I'll know my fate then.

Kim

 

[Frankklose]

The MD7 has third lamp the one which is not lit on start up. If this one is lit your engine is too hot.

The MD7 is difficult to bleed.

Start the engine and spray some quick start spray in the air intake and the engine will start. (WD40 will also do as quick start spray. Just do it not too often)

The starter motor must be running when you spry it in the intake, if the engine does not start you have a major problem. The MD7 is known for black smoke.

I think you have trouble with your fuel system. Old boat dirty or even cocked up fuel pipes.

 

[Frankklose]

To take the head of should be the last thing what you should try. The Cylinder head is often badly corroded and can’t be put back. Cylinder heads are no more available from VOLVO since years. Used ones if found are paid in gold….

 

[Abestea]

I had some problems with the 7A. The corrosion within the cylinder head was shocking. It had a lots of mineral deposits blocking the waterways. The water will still bypass the engine and out to the exhaust throught the pipe from the thermostat housing to the exhaust bend.

After a long run, i did have smoke from the engine inside the boat. I could not locate or recreate the condition. I could only assume that it was oil being burned off the engine.

My point? Do i have one The only answer may be what i did and recondition the cylinder head. Certainly drastic but i would take VicS 's advice first check the peripheries before drastic action.

 

[Leighb]

[ QUOTE ]
Thanks Vic

The smoke in the engine compartment was, I'm fairly sure, exhaust smoke.

[/ QUOTE ]

Have you looked at the exhaust injector bend? It is behind the manifold and the exhaust hose is fixed to it.

On my MD7A this was badly corroded, and exhaust gases and water were escaping. The previous owner had bodged it up with silencer bandage and binder twine /forums/images/graemlins/frown.gif

Engine ran fine however. A common fault is the exhaust hose, which may look fine on the outside may be collapsing inside and causing back pressure.

Some MD7As are tricky to bleed the fuel system. I believe all the MD7Bs were fitted with the Bosch injection pump which is easy.