Diesel compression tester

[spock500]

Ok, despite various attempts to her to start, gear oil, new battery, heat engine ect..it's a no go so have to consider the options and would like some advice on what to do -

Last time the head was off I noticed several score marks on one of the bores, at this point I did the leak down test with diesel with this cylinder comparable to the others.

I am going to pop the head drop the sump to release the pistons out the top, question is can this be honed or is this a re-bore jobbie?

Someone mentioned replacing the liners but this was in respect to another non merc engine?

 

[yachtman]

Ok, despite various attempts to her to start, gear oil, new battery, heat engine ect..it's a no go so have to consider the options and would like some advice on what to do -

Last time the head was off I noticed several score marks on one of the bores, at this point I did the leak down test with diesel with this cylinder comparable to the others.

I am going to pop the head drop the sump to release the pistons out the top, question is can this be honed or is this a re-bore jobbie?

Someone mentioned replacing the liners but this was in respect to another non merc engine?

how deep are the scores, equally how deep is the lip at the top.

rather looks as if you might have failed /broken ring or rings, unlikely to be able to hone out a deep groove, as normally honing is a finishing process for the rentention of oil I believe.

 

[Dieselman]

My guess says it's stuck rings due to caramalisation of the engine oil.

Pull the pistons out and check the rings, then run your finger nail round the bores.
That will probably hone out, even with hand rubbed wet 'n dry.
The rings may not even be toast if just stuck. If they are just stuck drop the pistons in a bucket of diesel for a week to see if they free off.

It will be interesting to see.

 

[lynall]

Shagged is the technical term

Wouldnt it be cheaper to get another engine that runs?



Lynall

 

[spock500]

Thanks for the replies chaps,

What's the best tool for removing the carbon (now that I have them all

Dremel with wire rotor brush?

It's got to be the only engine that's had three oil changes and never put a mile on the clock

 

[Dieselman]

shagged is the technical term:d

lol...

 

[Dieselman]

What's the best tool for removing the carbon (now that I have them all

No mechanical devices, they will knacker the piston.

just leave it to soak and see. The rings will probably come free then just scrape off the carbon.

An old broken ring is a good scraper for in the ring groves.

What you have there is what's known as 'bore polishing' and scuffing. I think it will rub out.
No harm in trying, it's free.

 

[spock500]

No mechanical devices, they will knacker the piston.

just leave it to soak and see. The rings will probably come free then just scrape off the carbon.

An old broken ring is a good scraper for in the ring groves.

Sorry bud, its was the carbon lip at the top of the bore - cant see 'em coming out with that still there?

 

[yachtman]

Sorry bud, its was the carbon lip at the top of the bore - cant see 'em coming out with that still there?

personally use a thick feeler gauge for cylinder edge carbon. followed by nylon scour pad.

 

[lynall]

Look in the for sale section member breaking 250 diesel w124.



Lynall

 

[spock500]

Cheers all,

I don't want to give up on the engine as it's a good lump, also like to try and keep things as original as possible.

Going to go with DM's advice and pop the pistons out which wont cost anything and can be done fairly easily.

Honing kit is about £20, new rings not sure (if needed) lets pull it aaprt and get some better detail

 

[Uberwagon]

For 20 quid i'd expect it to be a deglazing kit.

For removing the carbon, scotchbrite and diesel.

For cleaning the ring grooves, get a long roll of emery tape and using a long length in both hands clean most of the crap out. Afterwards try and find some pipe cleaners thin enough to get inside.

Dave!

 

[spock500]

For 20 quid i'd expect it to be a deglazing kit.

For removing the carbon, scotchbrite and diesel.

For cleaning the ring grooves, get a long roll of emery tape and using a long length in both hands clean most of the crap out. Afterwards try and find some pipe cleaners thin enough to get inside.

Dave!

Cheers bud, all advice greatly appreciated -

This is the three legged honing tool

http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&ssPageName=STRK:MEWAX:IT&item=300291438130

Is that about the right grit for the stones? I spoke to engine centre last week who have been very helpful, their advice was to pop it down the bores power on up and down 3/4 times then out - just enough to remove the glaze and no metal.

 

[Uberwagon]

I've only done honing on large liners and that experience tells me that getting a linear finish on used liners can be a pain in the butt.

It all depends on the speed of your drill.

Before honing there must be no carbon at all in the liner, lubricate it with diesel, as much as is practical and afterwards you want to see some good cross hatching. So imagine an X but flatter.

I couldn't say what kind of pressure the stones need to exert on the liner but you should feel them rubbing, but not feel like they are cutting.

You will know as it will feel right.

Dave!

 

[spock500]

Cheers for that,

Go the first one out, looks ok, perhaps even keep the rings -

Fingers crossed, lets hope they are all this good

 

[lynall]

Are you sure that engine was rebuilt? or have i read it wrong somewhere?



Lynall

 

[spock500]

I was trying to catch DM out but i guess he wasn't biting

That's not (thankfully) my piston, all five of mine are still in the block.

Stripped her down again and pleased to report that no perceptible ridge on the bores although some of the carbon is proving tough to get rid of.

just came in for a cuppa before doing the big heave ho to get the front end jacked up on ramps.

 

[spock500]

Ok, first piston is out - needed a small tap from underneath to get past carbon residue - as I did this and the piston released I felt something drop on my head, it looks like a piece of the oil scraper?

It was quite a gentle tap and unless these rings are very fragile its been like it for some time, I suspect this is what has caused the scoring on number two cylinder (this is number four).

Ignore the scoring on the middle of the crown, this is very light and my last attempt at jiggling the piston back and forth to free the rings.

Bore looks good;

Here's the main problem (apart from the above) the top two rings are completely flush with the side of the piston, no wonder she wouldn't start!

This looks to be where the ring joins, as can be seen it's fully compressed;

Ok, chaps what now? send the pistons away for reconditioning or are they ok as is?

If anyone has a OM605/6 and needs a bit of help I have done a 'how to' set of pics which I can post later.

 

[spock500]

In case anyone is following this it continues on here;

http://www.mercedesshop.com/shopforum/showthread.php?p=2155669#post2155669