Volvo penta md7b deceased

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mdonnelly

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Engine now out and problems with block and head. Opinion is possibily repairable but don't want to spend £500+ on taking a risk. Had spent almost £1000 18 months ago on repairs! Time to re-engine and considering my options. One train of thought is on a reconditioned engine. So is this feasable, folly or is new the best way to go? Would value opinions, thanks.
 
If you're prepared to fit a reconditioned engine, why not just repair/recondition yours? At least you know something of your engine's history. Might even be cheaper.
 
500 quid is cheap, compared to re-engining.. what EXACTLY is wrong with it ??..

Sorry, OVB, we seem to be following each others posts lol.. but exactly.. recon is recon..
too many rush out and simply buy a new unit imho.. often a total waste of money and time.

Joe.
 
The spares price's for old MD engine's would make any rebuild a foolish and expensive decision!! i.e. Top end gasket set not much change from £200!!!!

Paul.
 
Head gasket blown twice in 2 years. Needed head skimmed last year. Now head and blocked need skimmed as slight distortion on surfaces. Consequently pistons will need altered to accommodate this and have been told this will affect compression ratios. Unfortunately no clear answer as to cause of problems hence liklihood of occurring again.
 
Usual cause is simply overheating. If they chemically clean the block / head and reskim, there shouldnt be anything to worry about.
Get them to do a full strip and inspection and provide a warranty.

It is fairly easy to test for uneven heat distribution using an infrared thermometer gun with laser pointer (about 30 quid).
 
Machining won't be at Volvo prices! Have the work done at an automotive shop and get them to check everything out. This should not be an expensive job.

Sounds like you may have had a coolant problem in the past, distorting the head and maybe the block? Not having sorted the problem last time you are now in the situation that you must do it again (not baming you!) All the coolant passageways in the head need to be cleared, some may be blocked with salt/carbon/rust and will be hard to find.

If the engine is otherwise OK, oil consumption low, starts OK, not too rattly, I would definitely consider an overhaul. It will all be stripped for this work, so you can check bearings and replace if necessary. Seals can be replaced and you will finish up with a nice, reliable engine. But DON'T use a marine yard for the work, have it done by specialists.
 
Vyv, just been off the phone to guy doing the work. He is a relative who is a retired diesel engineer and who is doing the work purely for the enjoyment! He was actually disappointed when I was considering replacing it. Any how, he has basically stated word for word your opinion. So the plan is to get head and block skimmed and dependant on how much is removed whether it is feasable to continue. The car yard doing this is charging £40 for each face so wont be out too much for a possible definitive answer.
 
I can sympathise with your problem but I think you need to be objective. I agree with the comments about keeping your engine. It is unfortunate the head gasket went again. You need to find the cause, suggest you give more information to the forum.

As for a skim affecting the compression you add more shims under the block to get the corect dimension from block face to the top of the piston.

If it is any consolation, I re-engined last winter. After about 20 hours it seized up and bent the pushrods, water in the bores is the main suspect though nothing was proved. Probably my fault, it always is.

Stick with it at least you are not missing the season if you work on it now.
 
Just make SURE you have the block and head passage cleaned out at the same time, which involves a full strip.
Dont just go for a simple head block plane.

To the other poster who mentions shims ??.. can you explain, not the normal practice and cant see how it could work at all.
 
So if you are still sailing and have no time pressures it is another reason to try and sort your existing engine.

Captainslarty - I understood that Volvo engines have shims under the block to get the correct compression. Have not had my block off. You have me wondering now. The injector pump is shimmed as well.
 
With some engines it is possible to put in a thicker gasket to compensate for block/head skimming. No idea if these are available for that engine but definitely worth pursuing to save the trouble and expense of reducing the height of the pistons. Shims under the block sounds logical but I don't know the engine. If that is available it would be a far cheaper way to go.
 
To the other poster who mentions shims ??.. can you explain, not the normal practice and cant see how it could work at all.
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Perfectly normal practice on diesel engines to obtain the correct compression clearance in the cylinders.

Volvo often achieve this by having a shim pack between the cylinder block and crankase. In these cases the block is sandwiched beween the heads and crancase and should seperate quite easily even leaving the pistons in place.

No problem changing the rings or even the pistons and the shim pack should be adjusted during assembly to give the correct compression clearance after the block and head have been machined.

There is a maximum shim thickness recomended by volvo which will be given in the manual

This procedure does not apply to later engines where Volvo have taken someone elses engine and rebadged.
 
I have seen it in the manual. I can only access the forum at lunch time at work so do not have time. Perhaps someone could find a link to a manual for mdonnelly.
 
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