hmm if i were you i would try soaking number 5 with marvel mystery oil for a few days. Over that time continue to fill the cylinder up as it leaks down, keep it full.... Some people have had good luck with this method and some have not. But its worth a shot imo.

You could do that on any engine ever built and pressurise the crankcase.... piston rings make a lousy seal stationary, even on a brand new engine.

You do realise a head gasket blown across to an oil gallery will also pressurise a crank case....

This is why I am anti all these 99 different bull**** tests in a row.

remove the exhaust and intake manifolds, make up blanking plates, then pressurise the tract and that will tell you something, but who cares, you can't fix anything without taking the head off, so take the head off and let the dog see that rabbit.

Then, at least, you have a HOPE IN HELL of doing something none of these endless tests do, and detecting that you actually have two separate problems, fixing them both, and spending the next ten years driving your car without ever stripping the engine again.

Or you can just do a load more tests.... without really understanding what you are doing, and just pick the cheapest problem and go with that.... you never know, you may be lucky.

Hey, that sounds like a good idea, I was thinking of balancing an egg on the camshaft to see if the lobes were worn. :D

Ok, in seriousness, I think I'm done with the improvised diagnostic testing.

The last thing I did before I cleaned up for the week was fill up #5 with some 15W-40 and see how long it takes to drain. It doesn't. I interpret that as an intact piston.

Injectors are going back in for now, and I'm going to keep driving it till I can order parts for a head job and plan out a weekend to pull the head.

Thanks everyone for the help, I'll post pictures of the insides when I get the head off.


..one other thing.. what the heck does "let the dog see the rabbit" mean? I mean.. I had a Labrador, I trained him for birds, and every time he saw a rabbit he'd watch it run away before he got the notion in his head to chase it. Then he'd look at me askance as if to say "I don't think that was a bird, but whatever it was, weren't you supposed to shoot it so I could bring it back?"

Whats the big deal here? You have some kind of agression problem with pretty standard diagnostics. And for the record, the strategy of diagnostics presented by other posters is pretty darn logical, so far consisting of three tests in a page and a half of thread. Compression test, check. Verify valve clearances, check. leakdown test, check. Im looking around for the other 96 tests, but havent found them. :rolleyes:

A leak down test isnt exactly a difficult thing to do, way easier than just pulling the head and rebuilding it. It also has the utility of telling you what might be wrong in the first place, there is plenty of value to knowing that before embarking on a major and costly rebuild of the entire top end just cause "you have to do it anyway to fix anything".

people drive and maintain cars on a budget. Inexpensive easy testing procedures are extremely informative, and most importantly, don't break the bank.

If you go rabbiting with dogs... etc...

Esp a lurcher, so named because while most dogs will follow the rabbit track when chasing it down, a lurcher will always aim straight at the rabbit, "lurching" the corners.

That's why everyone likes them, cos they are easy and cheap to do.... that's it... end of.

An internet forum or a magic 8 ball has the utility of telling you what MIGHT be wrong.

The whole point of a test is it identifies if you have a problem or not, if you do (and it isn't a leaky injector, heater, or tight valve) then it's head off, no other possible way, not in any universe, not on any planet, to fix it, even if the head is perfect and it is a piston / ring problem, it's still head off.

People DO NOT maintain and drive cars on a budget, people trade on the remaining initial quality of a vehicle so that they can continue to cut corners and do shoddy maintenance and get away with it as long as possible.

For expletive deleted's sake, there are whole threads on here, a MERCEDES BENZ forum, about buying crap oil filters and saving a whole 5 bucks.

What do you call a guy who uses generic rubbers?

A cheap ****er.

Too many cheap ****ers buy old MB diesels and proceed to drive perfectly good cars into an early grave.

This isn't aggression Jack, I just hate to see perfectly good equipment trashed and driven into an early grave by cheap ****ers... THAT is aggression.

And I ask again, Mr. know it all, have you pulled the head on a mb diesel?

Yes, but never the same engine twice.... do it right the first time.

So, stating the painfully bloody obvious, that you HAVE to pull a head to do any internal valve / piston work, is all it takes to earn the label Mr Know It All is it?

What does that make your average diesel fitter, Brain of America?

I, for one, am looking forward to seeing what you find when you remove the head. BTW, did you study the valve action on number 5 while you were adjusting the valves?

I'm glad my doctor doesn't take your approach.

Valve action? :confused:
I spend a little time seeing if parts (rockers, valves, etc) have any abnormal play, is there anything else I should do?

Did you ream the glow plug holes before the compression test? What's the chance that debris got in between the valve seats causing the low compression? Could that spec of carbon bend a valve or will it burn off eventually with no remaining symptoms? How likely is debris from reaming causing such issues?

Lol, well, you can't be a guy who works on cars for a living if this is your diagnostic procedure. Also, spare us the "brain of America" BS please.

What do your represent, the "brain of the UK"? :rolleyes: Im not sure basic testing and common sense deserves to become a nationalistic issue.

You are lashing out with a stream of invective and aggression at VERY basic testing procedures which is pretty comical. Ill try your approach on the next possible customer I see.

"I didn't bother to do further tests because its a waste of my time to know anything else about it, and you don't want to be a cheap ****er sir, its not worth testing further because whatever the problem is, it will need 1000+ dollars in work. Also, if you DON'T allow me to pull the head right now at vast expense and time, you ARE a cheap ****er, so get out of my sight and think it over. Remember, here at **** you auto care, the customer is our top priority" :D

I see what you did there.

You had to put a whole string of words that I never said in order to try to make yourself appear to be correct.

What I would actually have said is this;

"I've checked for blowby on the injectors and heaters, and checked valve clearance, and you're 100 psi down on #5."

"There are three possibilities at this point, a valve problem or a bore problem, or a bit of both, though the compression test suggests it's mainly a valve problem, either way, the head has to come off, both for an accurate diagnosis and for repair."

"There is no point me doing any further mickey mouse tests or following any advice you printed out from an internet forum, because time is money, for you and for me, and none of these alleged tests are going to tell us anything useful."

"At this moment in time I know for a fact you'll need to fork out for a top end gasket set. That's it".

"You may need new valve seats cut, or new guides, but these are all fairly cheap jobs individually, the money goes in the labour, so let me work smart and do the job right the first time with minimum hours labour, and that way you both get your car back fastest, and 100% fixed, and the lowest bill in the long run."

Which is what I would actually say.

Which is about a million miles away from what you claim I would say.

And if the punter turned around and said "This guy on the internet reckons that's the wrong way to do it and there are lots of better and cheaper ways of doing it." I'd answer them.

"No problem, go and give your car to the guy on the internet, and when it all goes wrong and you come back here your bill could well be five to ten times as high, because I not only have to fix the existing small problem, but also every problem you create in your tests and attempted cheap repairs, plus the wear and tear of continuing to run an engine with bugger all compression on #5..."

Car owner "So you don't think it is a good idea to listen to the internet guy then?"

"Well, it depends, my bank manager will think it is a great idea..."

There is the right way to do a job, and there is every other way, and the right way is ALWAYS the cheapest way in the long run, even if you value your time at zero.

Those of us who are competent do not value our time at zero.

Daddy?