my buddy came over and we changed oil in our cars. i told him to turn his engine on and see how much blowby he had. he was confused and started his car. the oil cap seemed heavier than my 300D cap, and it was almost dancing off the engine block. this is with the plastic cover on the engine, with the cap being lower and in a type of groove. i was very supprised at this and showed him my car. my 85 300D has 173k on it, and the cap would not move when i loosened it.

so my question is this, is blowby a universal phenomenon for diesels? he has been telling me how his jetta has been hard to start and very cranky on cold mornings. this would agree with the blowby test, as he should have lower compression. his 98 jetta has 160k on it.

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Grey '91 350SDL 214k Dad's car
Beige '81 240D 4 Speed 254k SOLD
Blue '82 300D 225k SOLD
White '95 E300D 46k SOLD
Blue '87 190D 2.5 Turbo 315k SOLD
Brown '80 240D 4 Speed 716k SOLD
Beige '80 300D N/A 119k SOLD
Blue '85 300D Model 186k T-Boned

blowby test is reliable indicator of motor wear on any internal combustion motor.

tom w

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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.

I think it would also depend on how the crankcase is vented. I had a Nissan diesel pick up and all it had was a vent pipe on the side of the engine pointing down, something very similar to what was on pre-1955 gasoline powered cars and trucks (for those of you old enough to remember those). You could take the oil cap off and it had no blow by but you could see it puffing out the pipe a little. That pipe did make one heck of a mess on the suspension components it was draining on though.

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DJ


84 300D Turbodiesel 190K with 4 speed manual sold in 03/2012

That's right, venting is everything. I used to make blow-by measurement systems (NTK's M100 et al). You could measure the flow through the road draft tube on a diesel by putting a flowmeter inline with it. But if the tube recirculated back into the intake (like on a OM61X) then the flow would be the blowby + the intake vacuum. To complicate matters further, the diameter of the road draft tube/recirculation tube would cause more or less flow restriction...thus making it futile to compare actual liters/min of flow between different crankcase vent setups. In fact, if you used the flow meter with 6' of road draft hose or 2' you'd get different answers because you were changing backpressure. I got a lot of tech support calls on this.

He may have worn rings. But if the car doesn't smoke and makes good power, don't sweat it. The key is to check it against a new 98 jetta...not a MBZ.

I'm not sure about a 98 jetta, but my Rabbit vented to the intake. Tell your pal to check his crankcase ventilation system and PCV (if it has one).

Good luck,
Yoko

funny how you said smoke, because he smokes a lot. it is blue also. in addition, when we changed his oil, he said it was low on oil and we were only able to get 2 quarts out of it. it takes 4.5 quarts to fill up. this was on a 5k miles interval.

it sounds more and more like a worn out engine to me.

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Grey '91 350SDL 214k Dad's car
Beige '81 240D 4 Speed 254k SOLD
Blue '82 300D 225k SOLD
White '95 E300D 46k SOLD
Blue '87 190D 2.5 Turbo 315k SOLD
Brown '80 240D 4 Speed 716k SOLD
Beige '80 300D N/A 119k SOLD
Blue '85 300D Model 186k T-Boned

Every internal combustion engine has blow by. For diesels it is just death because they need compression to ignite the fuel. A low compression gas engine will run for a very very long time.

I am not sure how to measure it on our cars. I think on the larger diesels they measure crank case pressure. I saw someone do it once on a 6v92TIB but I am not sure of the specs or procedure.


If it runs good ignore it, the only fix is a rebuild.

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1999 SL500
1969 280SE
2023 Ram 1500
2007 Tiara 3200

Raise the RPM a bit while watching the loosened oil cap to eliminate engine vibration as a factor.

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2004 VW Jetta TDI (manual)

Past MB's: '96 E300D, '83 240D, '82 300D, '87 300D, '87 420SEL

It would depend I'm sure on the crankcase ventilation system, and whether it is operating correctly.

In the 6V92 Detroit it is a 2-stroke, supercharged & turbocharged, crankcase pressure is dependent on the blower to feed the air to the cylinders.



- Jeff Miller
M-B 190DT "Ruby II"
Audi 4KQ ("Audri" bought new, 200k miles all original)
Vanagon Syncro VR6 (shop truck, needs a TD)
VW Cabriolet (Daughter's)
Econoline Conversion (Wife's)

his engine was not shaking the cap off, the plastic surrounding the oil cap was keeping it from falling off the top of his engine, and since it had no where to go, it was dancing around.

that is a bummer. he bought the car thinking it would last him a long time, but i dont know how i want to tell him. sorry dude your car is going down...?

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Grey '91 350SDL 214k Dad's car
Beige '81 240D 4 Speed 254k SOLD
Blue '82 300D 225k SOLD
White '95 E300D 46k SOLD
Blue '87 190D 2.5 Turbo 315k SOLD
Brown '80 240D 4 Speed 716k SOLD
Beige '80 300D N/A 119k SOLD
Blue '85 300D Model 186k T-Boned

Does he even bother to check the oil? You should never let it get that low.

It just sounds like an abused engine, drive it till it won't start or sell it and let the next person deal with it.

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1999 SL500
1969 280SE
2023 Ram 1500
2007 Tiara 3200

Could be several things:

TDI's are notorious for clogging up the EGR, intake manifold and breather system especially if regular oil was used instead of synthetic. It is possible that his breather system is partially plugged up. That would certainly explain the excess blowby. A little exploratory surgery is in order to make sure the breather breathes....

Has he checked the glowplugs? Diesels don't like to start without them.... Poor glowplug performance or a weak battery can make starting difficult. Check it out.

Its pretty normal to use a quart or two in 5000miles in a higher mileage engine. I suggest he check his oil a little more regularly. Being two quarts down is a bad thing. I check my oil weekly at a minimum.

A compression/leakdown test is the only definitive test that will tell for sure that the engine is toast. Even if the compression is marginal, this will make it more difficult to start but it will run just fine once started. This is where the strong battery and good glowplugs come into play. My wifes old Jetta with 300+K on it would start at 10*F after sitting 12hrs. in the Amtrak parking lot. Big battery, upgraded battery cables and good glowplugs are the answer.
RT

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When all else fails, vote from the rooftops!
84' Mercedes Benz 300D Anthracite/black, 171K
03' Volkswagen Jetta TDI blue/black, 93K
93' Chevrolet C2500HD ExCab 6.5TD, Two-tone blue, 252K

he just replaced all of his glowplugs, so that is not he issue. i will tell him to research the EGR and breather system, that will teach him to learn some stuff on his own.

and the oil well he said he checked it and he knew it was low. but when we pulled only 2 quarts out of it was a little stunned. he will check it more from now on. also he just switched to sythentic. he was running rotellaT 15-40 in it before, and yesterday he wanted to run synthetic rotella in it.

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Grey '91 350SDL 214k Dad's car
Beige '81 240D 4 Speed 254k SOLD
Blue '82 300D 225k SOLD
White '95 E300D 46k SOLD
Blue '87 190D 2.5 Turbo 315k SOLD
Brown '80 240D 4 Speed 716k SOLD
Beige '80 300D N/A 119k SOLD
Blue '85 300D Model 186k T-Boned

I'd still try raising the RPM. I had this experience with my 240D when it was warmed up and I was doing this test. At normal idle my cap was dancing violently and it fell off a couple times even though the engine didn't look like it was shaking. But when I raised the RPM just a little bit, the cap was rock steady.

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2004 VW Jetta TDI (manual)

Past MB's: '96 E300D, '83 240D, '82 300D, '87 300D, '87 420SEL

What kind of oil does he use? I know back on the TDIclub everyone has been saying that if you have the wrong oil in the car the engine will get alot more wear and will eventaully die. Ask him if he has used oil that was 505.00 or 505.01 approved.

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Current:
05 E320 CDI
07 GL320 CDI
08 Sprinter
05 Dodge Cummins
01 Dodge Cummins

Previous
2004 E55 AMG
2002 C32 AMG (#2)
1995 E300
1978 300D
1987 300D
2002 C32 AMG(blown motor :[
1981 300SD
1983 300SD
1987 300SDL
2002 Jetta TDI
1996 S420
1995 S500
1993 190E 2.6
1992 190E 2.3
1985 190E 2.3 5-Speed

FYI. . .synthetic 5W40 is what should be used in a TDI, year round, according to VW.

rwthomas1: Thanks for the tip on the battery/updated cables/glow plugs.

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1983 300SD - OLLIE
1985 300D-HILDA (SOLD)
2002 VW Jetta TDI - Puddles
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Diesel passt mir leid!