Retorquing After Rebuild - Volvo Penta MD2040

[cainiao]

We had our engine rebuilt in Feb and the mechanic told us to retorque the head bolts at 50 hours. We just hit that and unfortunately there aren't really any mechanics handy. I'm not squeamish about getting my hands dirty, but I'm not very experienced with diesel engines yet. I have a torque wrench and a workshop manual, but the manual isn't super helpful. It describes how to strip and rebuild the engine, but there aren't instructions for what to take apart to retorque the head bolts.

My question is two-fold I guess:

First, how important is this? Can it be postponed until we get somewhere with someone who knows what they're doing?

Second, what really needs to be taken off to do it? Is it just the valve cover, or do I need to take off the heat exchanger/alternator/injectors/oil pressure pipe/etc as described in the teardown in the manual?

[Lepke]

It can wait. You only take off the valve cover. You may need a new gasket.
I don't know your engine, but all the other engines I have rebuilt have the head bolts on the top of the head. You remove the valve cover. Some bolt heads could be outside the valve cover, but some are under neath the cover, too.
The bolts usually are in each corner of the cylinder. If you look from the end of the engine you should see two rows of bolt heads once the valve cover is removed.
Most engines have a sequence for tightening the bolts. Usually starting from the center bolts and work out toward the ends.

[cainiao]

Thanks. I'll get out the part diagrams and have another look at it. Good to know things won't explode if I don't do it right this instant.

[NoTies]

Retorquing bolts is pretty much a thing of the past with modern engines but if you go ahead you may well need to remove the rockers as well to access all the bolts. Either way, you will need to readjust all valve clearances once done,

[a64pilot]

Originally Posted by NoTies

Retorquing bolts is pretty much a thing of the past with modern engines but if you go ahead you may well need to remove the rockers as well to access all the bolts. Either way, you will need to readjust all valve clearances once done,

This, I can't think of any engines that removing the rocker arms wasn't required, maybe a GM small block?
Anyway retorque requirement is I believe based on the type of head gasket, old school gaskets yes, at least since the 1970's Fel-Pro blue head gaskets don't.
Not retorqueing may result in a blown gasket, but my experience is head gaskets have only blown from engine being overheated, and often head warped too.


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[Xthewater]

Being from old school and long time mechanic I would say retorque head bolts, particularly on a diesel.
Diesels run on compression ignition so there's about twice the compression pressure than a petrol engine.
The heat cold cycling tends to stretch the head bolts until normalizing, bolt stretch which can lead to head gasket leakage. If that happens then you're up for at least upper disassembly to replace gasket, not fun and expensive. Then you're up for another 50 hr and retorque or if not.......start at beginning and reread.

Torquing must be done in a cross hatch pattern to ensure even crush pressure over cylinders and no head distortion which can lead to cylinder leakage.

Likely have to remove rocker assembly to get to some of the bolts which means re adjusting the valve lash but even if not you'll have to re adjust. It's a good learning experience.

[a64pilot]

Read, and follow both torque sequence and torque procedure, it differs a little from one engine to another.
Being not so smart, I mark the bolt head with a piece of chalk to show me where I am on the torque sequence, wipes off easily of course

[JTHAW]

Originally Posted by Xthewater

Being from old school and long time mechanic I would say retorque head bolts, particularly on a diesel.
Diesels run on compression ignition so there's about twice the compression pressure than a petrol engine.
The heat cold cycling tends to stretch the head bolts until normalizing, bolt stretch which can lead to head gasket leakage. If that happens then you're up for at least upper disassembly to replace gasket, not fun and expensive. Then you're up for another 50 hr and retorque or if not.......start at beginning and reread.

Torquing must be done in a cross hatch pattern to ensure even crush pressure over cylinders and no head distortion which can lead to cylinder leakage.

Likely have to remove rocker assembly to get to some of the bolts which means re adjusting the valve lash but even if not you'll have to re adjust. It's a good learning experience.

This is your answer!

[seabreez]

My question is two-fold I guess:

First, how important is this? Can it be postponed until we get somewhere with someone who knows what they're doing?

I have rebuilt many marine engines from Volvo gas to diesel to GM, Cat etc. The re-torqueing is a thing that I never did, even when recommended I never did it. When an engine is rebuilt with quality parts or original equipment parts, you should never have to go over this again. if the rebuilder is meticulous about doing his or her work. The head bolts threads are sealed when installing and therefor you would be disturbing that seal and the re-torqueing would not be accurate in any case. Then if you need more torque to break the seal you risk over tightening. Leave it alone if it is running properly. It's me...

[Horus]

I'm with Seabreez; don't touch it! (On a good running engine) Re-Torqueing is indeed not for these 'modern' (VP/MD2040) engines.

[deblen]

Page 32 in this manual shows the sequence of bolt torquing.

http://www.bluemoment.com/manuals/Vo...0-20-30-40.pdf

Your engine is an Ishibaura. Forget Ish. model # but it was posted on here within last month or so.

Perkins sold same engine as a Perama M40

These engines were used in many land based tractors,mowers,etc. & parts are available from land eqpt dealers much cheaper than VP or Perkins.

A real good engine series!

[a64pilot]

Originally Posted by seabreez

My question is two-fold I guess:

First, how important is this? Can it be postponed until we get somewhere with someone who knows what they're doing?

It's not important at all, until you blow a head gasket.
How likely are you to? In my opinion the overwhelming majority of engines don't get their heads re-torqued, and yet head gasket failure is pretty rare.

Not trying to be smart, but I guess it depends on how lucky you feel, for example I can't think of a single new Diesel engine I have bought in the last 20 years, Volkswagen, Duramax, John Deere etc., that required the head to be re-torqued.

But, I re-torqued the head on my 29 yr old Yanmar a few months ago, cause I don't know if it ever has been, and it can't hurt, took maybe an hour, a two beer job, but I've re-torqued a few heads.

[Barney21]

As previously stated modern head gaskets dont need re-torque Felpro dont stipulate it . The proceedure I used to take with old copper and composite gasket was take each bolt out completely clean and wash the treads put a small amount of sealant on each thread and reinstall , obviously do it one bolt at a time engine cold.
If you just re-torque with bolt in place you will have to "crack" the thread in the block and this by itself will give you an incorrect reading. All that said if the engine rebuild was done in the last 10 years it is more likely to be a modern gasket. That being said the mechanic told you to do it ,so maybe he used the old style gasket.

[seabreez]

Not trying to be smart, but I guess it depends on how lucky you feel, for example I can't think of a single new Diesel engine I have bought in the last 20 years, Volkswagen, Duramax, John Deere etc., that required the head to be re-torqued.

But, I re-torqued the head on my 29 yr old Yanmar a few months ago, cause I don't know if it ever has been, and it can't hurt, took maybe an hour, a two beer job, but I've re-torqued a few heads. [/QUOTE]

You just gave me a "second the motion". After 29 years you re-torqued the heads and two beers. Thanks for supporting my thoughts on re-torqueing. If you would not have re-torqued the heads you would have had time for more beer... Cheers...

[tinkrman69]

Originally Posted by Xthewater

Being from old school and long time mechanic I would say retorque head bolts, particularly on a diesel.
Diesels run on compression ignition so there's about twice the compression pressure than a petrol engine.
The heat cold cycling tends to stretch the head bolts until normalizing, bolt stretch which can lead to head gasket leakage. If that happens then you're up for at least upper disassembly to replace gasket, not fun and expensive. Then you're up for another 50 hr and retorque or if not.......start at beginning and reread.

Torquing must be done in a cross hatch pattern to ensure even crush pressure over cylinders and no head distortion which can lead to cylinder leakage.

Likely have to remove rocker assembly to get to some of the bolts which means re adjusting the valve lash but even if not you'll have to re adjust. It's a good learning experience.

i'll second this.

With your statement of "no experience" maybe you should wait but not long,,,at the very next opportunity, even if your schedule is delayed. Find a mechanic or better a cruiser/machanic that will show you how. these are things a cruiser should know. I know women cruisers that have learned to do these things. You can learn this if you're willing. It's all really simple. intimidation is the only thing that makes it scary and that is self imposed.