OM617 leak down test + valve spring removal question
 

Dear All,

I've had problems with oil ending up in my inlet / exhaust manifold =>

http://www.peachparts.com/shopforum/diesel-discussion/276144-om617-manifold-oil-%3D-broken-valve-guide.html

(1981 W123 300D => OM617)

Unfortunately cleaning it up and tightening stuff hasn't worked so I'm now on a mission to check some things before I strip and rebuild the cylinder head.

I'd like to do a leak down test before I take it all apart (I hope it is just the head!). Does any one have any tips for this? Good / reliable tools? Cheap but effective DIY alternatives? Time saving advice? Links to good threads?

I expect I will have to check the valve guides, which will mean I'll have to dismantle the valve springs etc etc. Do I need to buy one of those expensive SIR tools valve compressors?

Any help you can give will be greatly appreciated.

On a OM617 you will not need a Valve Spring Compressor. However the Piston will need to be at Top dead center or very close to that so that the Valves will not drop inside of the Cylinder.
The Service Manual will tell you what you need to do to. Look in the section that has replacing the Valve Stem Seals.
I cannot remember exactly but I believe the manual also has the Leak Back Test in it.

For those in the USA:
Harbor Freight sells a Leak Back Tester. But, since it is made for Gas Engines it only has Spark Plug Adapters.(You need a source of filtered compressed Air.)

If you have the Harbor Freight Compression Tester one of those adapters might be able to be used.

If all you want to do is listen to where the Air is leaking from you would only need one of the Compression Tester Adapters connected to the filtered compressed air.

On the Harbor Freight site if you click on the item often you have access to the instructions in PDF form.

ditto on all of the above.

use compressed air in an injector hole with a rubber grommet.

I have the HF set. It is low quality but works (I've only used it on gassers) if all you need is a tube between your air compressor & engine hole.

Right thanks folks - great help as usual!

(Some times thinking about doing a job is worse than actually getting your hands dirty)

I'll just do it.

The attachment is from the service manual.

Thank you very much kind Sir.

^ You're welcome, good luck and keep us posted.
They also provide a way to test the head once removed from the engine, but I think you need seriously specialized equipment, a pressure plate designed specifically for that purpose, a suspension device as well.

You want:
HF leakdown tester
Injector adpater from HF diesel compression tester w/ schrader check valve removed.

You want to read the instructions from the leakdown tester before attempting to use it.

Wow I just searched for "cylinder pressure tester" and came up with this:-

http://www.amsequipmentsales.com/Pressure_Tester.html

(Slightly out of the average home mechanic's reach)

Here's a link for a cylinder leak down test procedure (I case anyone else needs some more information)

http://www.carcraft.com/techarticles/116_0406_cylinder_leakdown_tester/index.html

Right here's an update:-

I bought a pressure leak test gauge but it came without instructions. I don't think they would have helped anyway as most of the instruction booklets I've received with Chinese made tools are virtually incomprehensible... So I did the next best thing and found a film on You Tube with a similar looking bit of kit:-

http://www.youtube.com/watch?v=UOHYrf4dJzM

So I've got a pressure tester that you wind up to a "set" pressure on the % gauge and then connect it to the cylinder you are testing. The pressure drops and you read the output on the gauge.

Whilst using this bit of kit I noticed that if you don't have the same input pressure (shown on the input gauge) then you can get a false comparison between the cylinders you are measuring.

To find TDC for each cylinder I unscrewed the injector and fitted the pressure leak attachment. I then rotated the engine until air started to come out of the engine - so the compression stroke. I then stopped turning the engine when the air stopped.

I got the following results on a COLD engine:-

Cylinder #1 60%
Cylinder #2 65%
Cylinder #3 55%
Cylinder #4 55%
Cylinder #5 55%

The input pressure for all of these measurements was 7.5 PSI according to the inlet pressure gauge. Not a lot eh?

All of the escaping gas seems to be coming out of the oil filler cap.

There are no bubbles in the coolant. No sound at the exhaust. Hardly any sound at the oil filler pipe. Hardly any sound at the air intake.

So I guess the valve seals need to be replaced at the very least.

Does any one have any comments?

QUESTION:-

Is it likely that the pressure drop would be greater on a warm engine?