x2 leak down test first

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Thanks,
Mark in NC

"Spark plugs?...We don't need no stinking spark plugs!"
1985 300SD "Der Silberne Schlitten" 420,000 mi


Wish these were diesel:
2003 Ford Club Wagon 130,000 mi

Lacking a real leakdown tester, I rigged up a 20 psi regulated source to the compression test fitting (See picture, sorry about the quality)



It's pressurizing the crankcase.. If I hold my hand over the crank breather, I can feel the pressure. If I hold it over the compressor inlet, nothing. Sounds like it's blowing into the crank, can't hear anything in the exhaust.

Hole in the piston?

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'82 300SD 351k

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.

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?"

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'82 300SD 351k

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.

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?

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

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'82 300SD 351k

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.

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.

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This post brought to you by Carl's Jr.

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?

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

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"? 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"

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This post brought to you by Carl's Jr.

Daddy?

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CC: NSA

All things are burning, know this and be released.

82 Benz 240 D, Kuan Yin
12 Ford Escape 4wd

You're four times

It's hard to

more likely to

concentrate on

have an accident

two things

when you're on

at the same time.

a cell phone.

www.kiva.org It's not like there's anything wrong with feeling good, is there?

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.

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1985 300TD Turbo Euro-wagon
1979 280CE 225,200 miles
1985 300D Turbo 264,000 miles
1976 240D 190,000 miles
1979 300TD 220,000

GONE but not forgotten
1976 300D 195,300 miles
1983 300D Turbo 175,000 miles

http://i42.photobucket.com/albums/e3...e485-1-2-1.jpg

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?

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85 300D turbo pristine w 157k when purchased 167,870 July 2025
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

Here's my take on the situation. I'm in the US but I am a UK citizen. It appears that such things are relevant to this problem somehow.
At 304k miles, the engine is reaching the limits of it's serviceable life. So in my mind, the question is whether it is worth doing anything more than just a head job on it. If you can confirm via a leakdown test that the valve is the culprit, you face a simpler decision. Is the car and engine worth the cost of a head job? The cost of a complete engine rebuild is far higher and involves much more work. If the valves are seating well and the leakdown test points to a ring problem, it might be better to simply continue driving the car while looking for a low mileage replacement engine which would be much cheaper than rebuilding the existing one.

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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13