The mercedes diesel oil cap (aka blow-by) test- Fact or fiction?
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- เผยแพร่เมื่อ 26 ส.ค. 2024
- Mercedes source has always told potential classic Mercedes buyers to beware of cars that have a hovering oil cap.
this is bad information....
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good post. lots of blowby by the microphone
yeah...outside...windy day
🤓
LOL
Any real mechanic knows that if you used this method you obviously don’t know what is blow by . The oil pressure can cause oil to fly out and people like woah that’s not good . The timing chain can cause pressure . There’s car with massive blow by that will run like a champ .
Well I’m certainly glad I followed Pierre‘s advice regarding ( or disregarding) the blow by test… I’m the guy he mentioned above, and while the cap was definitely dancing pretty high for me, the car cold starts within one or two revolutions even with minimal glowing - which now I understand is really the true test. Thanks Pierre!
your car needs a valve adjustment. and it IS a great car.
Thanks for the great info! I just acquired a 1982 240D today with 276,000 miles. It has quite a bit of blowby at idle, but runs and drives perfectly fine. I’m excited to do a valve adjustment, a diesel purge, and changing all fluids and filters. The only real issues I’ve found so far is the freon needs recharging and dash lights do not work.
Who is going to drive over and tell Kent?
If you buy his oil it will help !!
Oh boy.
Lmao..... killed me.
Doesn't he make a special kit for testing blowby, with a paper towel to keep your fingers clean, and a ruler for checking how high the oil cap is bouncing?
@@gotham61
He's the only one who is laughing on the way to the bank.
Thank you for shinning light into this topic.
my pleasure
Yes yes yes ! This video couldn't of come sooner ! me and a friend were just debating this ! My grandpa used to say on his old tractors when you start to get blow by it's not broken it is "broke in"
regardless, it is true
Excellent presentation. The fellow in the lab coat will not be happy!
That guy is never happy. You take your car to him and it will cost you a fortune
@@marcelcovaci9922 Kent just posted a new video a few days ago. He’s considering buying a really roached out 300 sd. At about 1 minute into the video he makes a veiled reference to Pierre as one of those folks who thinks every one of these cars should be restored. Kent says he disagrees with that.
Good sound advice from an expert with a passion for the car
Not a passion for selling gadgets kits and info.
I fully agree, I have a modern diesel “4n15” 2.4 DID. It has blow by, runs great, no oil consumption, start immediately, fuel consumption like new. But I see lots of blow by.
Thanks for "hammering home" the more precise tests to know about an engine. If a prospective buyer relies only on "cap dancing"------and sees that the valve cover hasn't been off for decades---obviously no recent valve adjustment
you're most welcome
It’s funny I was thinking the same thing about the valves being out of adjustment or carbon being on the seats potentially causing a lot of blowby and not being serious. I think it’s interesting Pierre has an example that shows no blowby from that test that has done thought. It really matters how much is getting into the crankcase. Also a great point about a weak battery or bad glow plug relay potentially being thought as a worn out engine! Great stuff Pierre these videos are addicting love learning about these amazing vintage Mercedes-Benz
Great info once again. Thank you!
This confirms to me more why my om602 turbo has blow by but starts sound idles and performs perfectly with zero oil consumption , thanks for this valuable advice 🙏🙏🙏🙏💯💯
I've always wondered about the blowby test. It's not a diesel but my W201 190e 2.0 petrol with 180,000 miles has a jumpy cap at idle but between 3,000 to 5,000 mile oil change intervals there is no obvious oil consumption on the dipstick and no requirement for topup. About 10 years ago I started using fully sythetic oil and rather than being black at oil changes...the oil is now a dark amber. In the past the engine used to need topping up with oil regularly but that may have been due to a broken breather hose and oil valve stem seals which were replaced. The idle is not 100% smooth and sometimes it doesn't catch on the first crank, giving it new injectors and regular TLC seemed to bring back some missing power and I'm happy(ish) to live with a jumpy oil cap! Although my 420SE V8 with 150k miles...the oil cap does not jump at all!
nature of the beast.
Wow! I'm glad that I found this channel! Thanks for that!
You're welcome!
Why valve adjustment affects blow-by? Theoretically it should only affect the compression. When valve is not fully closed you cannot compress the mixture but it shouldn't be pushed into crankcase, only into exhaust or intake..
Thanks for the Info
I noticed the blow by test wasn’t reliable when I did that “test” to my W123. If you try to loosen the cap and let it sit over the valve cover, it almost goes flying and oil splashes all over the place, yet the car starts really easy, has lots of power, burns less than a quart of oil every 6k miles (2 oil changes), and doesn’t smoke.
That is not a test, is a waste of time and a mess and you shouldn’t conclude anything from it.
That's what I've learned as well.
Cyl leakage test, then compression test. Then oil consumption. and one you can do when buying is a cold start test. But failing a cold start test could mean only it needs the valves adjusted (OM 61x, OM62x, OM636) I never had much, if any, faith in the oil cap test. Besides, I was trained by the OM621 to NEVER try to run the engine with the oil filler cap off. If you don't believe me, Try it yourself, looking into the oil filler while an accomplice starts the engine. Please also have a second accomplice video the episode and send it to us! I can't wait to see it!
My 240D had blow-by (dancing oil cap) for the last 15 years. Starts every time, uses 0.5ltr oil in 5000 kms, so you're right, this test is not the right indicator how bad the motor is.
Great take on blow by... ❤❤
Very interesting topic. Bought a 370,000 km 97 C250 Turbodiesel that fails the blow-by test but starts at the first revolution of the crank when cold, pulls hard and doesn't smoke at all. So far, no measurable oil consumption either.
Thanks pierre good to know
Just found your channel... I owned a 300CD (Turbo) in the past. Would you say exhaust color/amount is a better indicator of potential issues, including whether it smokes during cold vs warm starts, acceleration, etc?
I agree that it can be a good indicator for an engine when an engine passes but also doesn't mean much when an engine fails. I have a 1980 300SD with 185,000 miles that runs perfectly and has no blow-by at all. I also have an 140,000 mile engine from a 77 240D that has excessive blow-by but it also runs perfectly, idles smoothly, and makes a lot of power (relative to other 616s). Both start cold with the bump of the key which I would agree is a better test of engine health.
exactly/
My 240d has zero blowby on cold startup. But when it reaches operating temps there is quite a bit of blowby cap dance on idle. But it goes away when the rpms are raised. Actually it creates a vaccum on the cap when the rpms are raised. I'm confused, what is my scenario?
I’m planning to do a liqui moly pro line engine flush and use visco plus to improve piston ring/wall seal hopefully as all liqui moly products I used before work like magic
Come on Pierre, don't hold back now. 😁 I'll have to admit that I did in fact use this test on the first few cars I looked at. Of course they had tons of other issues as well so that little so called "test" wasn't really a factor. Ultimately I found a car that was pretty good and just needed some TLC.
I prefer the other method.
Hot engine, remove the oil breather pipe from cambox and block it simultaneously start stop watch....
Time till engine stops.
The crankcase back pressure operates on reverse side of the vacuum stop device.
Mine is currently 34 seconds before stop.
A poor one is about 5 seconds....
Thanks for the video, but do you really "dial in" and alda? Or is it adjusted to compensate for other underlying issues?
Thanks for speaking on this. I recently acquired an 83 240d manual that doesn't pass the blow by test, but fires right up on 20 degree mornings and moves right along with little to no smoke.
haha...because said test is irrelevant
Congrats 👍🥳 !. Congrats again , there so many other little light things , things liked , motor mountain , transmission's mountain , if it a manual transmission and so on !..
Good info, thanks.
There is no PCV valve in these engines since no manifold vacuum to suck thru a valve. Instead, just an open tube from the top of the valve cover to the intake after the air filter. The only pressure drop to suck blow-by gases into the intake is from the drop across the air filter. Thus, if a dirty air filter, you may not see blow-by when you remove the oil fill cap since it is flowing to the lower pressure after the air filter. There is always some blow-by past the piston rings, so if you see it coming out of the valve cover, it might be more due to a new air filter with minimal pressure drop. Conversely, an unscrupulous seller might demonstrate "no blow-by" by wrapping a rag around the air filter to increase the pressure drop. To take the air filter out of the picture, remove the valve vent and plug it so all blow-by must exit the oil fill cap.
Perhaps a better test I read is to leave the oil cap tight, run engine with vent disconnected from the air filter, then plug it with your thumb and see how long before the engine stops. An excellent engine engine should run >10 sec and a worn one die in
my 201 m102 engine has a jumpy cap at idle, a few wisps of smoke from the cap when fully hot. never burns oil, runs super smoothly over 1000rpm, i have put a small inline filter on the breather hose from the air cleaner to the inlet manifold which does catch oil, just to keep the inlet valves clean.
almost all m102 engines do it, too. mostly due to worn valve guides
Fantastic summary.
Nice explanation and advice!
I agree , my om602 turbo has blowby , it starts instantly accelerate amazing sounds amazing and use zero oil , idles like brand new engine , I think the reason for blowby is cos I bought the engine from
Junkyard and probably was sitting for yeaaaaaars ( engine looks like it had very low mileage )
Great advice cheers dude viewing a 300d in the morning.
83 300 sd with over 400,000 mi.
Slight oil cap dance. No oil consumption. Easy starts. Strong performance and great fuel economy. Oil change every 3,000 mi, filter and fuel filters. Valve adjustment every couple years. Liquid Moly German fuel treatment. Tried Kent's diesel purge...and got nothing. Just basic maintenance and care.
Hi buddy is the w124 with a 300D good or a lemon thanks
Some very wise words sir!
Thank you for Great Video. Another topic is white smoke. Where is PCV valve on that car?
Great content! Can you share some info about getting the most power from an OM616. What is your opinion on adding a turbo to a 240D? I dont want to do a swap, love the rattle...
Thanks
Mechanical engineer here...spot on.
Additional point: oil analysis with each oil change until a baseline is established than every six-months. An oil analysis will tell you more about whats happening inside an engine than if you were to shrink yourself down to the size of an atom and get blown out the exhaust pipe!
That said, I hate Kent as the guy is a scam artist with his videos, kits, and instructions. They are nothing more than a rewritten factory service manual!
Thank you for chiming in, Kyle. I tried to tell people, they don't believe me
Would this discussion apply to a m102 engine? 8valve not the 16. I have lots of blowby at oil cap , yet burns no oil, no smoke out tail pipe at all. Starts immediately. I’ll try the 1500 rpm test and see if it abates at that engine speed. Car had been sitting many years. In a garage, but no use at all during that time. A conundrum.
nature of the beast. might be a sign of bad valve guides but certainly not a sign of a worn bottom end .m102 engine bottom end is mostly bullet proof
I wonder if the age and condition of the oil has any effect on blow by. A few years ago, I owned a Corolla station wagon and the owner manual said something about the engine oil level going down after a long drive. It stated that over time the oil absorbs moisture and that after a long drive it would burn or evaporate (don’t remember quite well). Therefore, if that were correct, a car with old engine oil would have some moisture that would evaporate when the engine heats up. Perhaps that’s part of the steam you see coming out of the valve cover.
If you're looking at a used car then I think it absolutely does, especially when it has not been maintained well
I see what you mean, oilcap test is crap. But correct blow by test is OK. Better than compression measerment - becouse it does not depend on valve clearence, strarter motor condition, battery and all of that, but compression is dependable. Measured with domestic gas meter while engine is worm running idle. My OM616 is now 100liters/in 60 sec, so it is dead. Under 25 liters/ in 60s is still OK.
In the grand scheme, blowby is inconsequential. Compression matters.
I suppose that this also applies to gas engines?
What does “i dialed in the elda” mean?
even though you don't have a lab coat i still find you very credible
Great video. Thank you !
is it possible to determine Burning Oil on a om617 with a Veggie Oil two tank system? Mine has blue smoke and i want to chase the source, but it i would guess that running veggie oil fuel would show inacurate indications of burning engine oil
I’ve got a 09 r320 with the on642 engine in it.
It’s consuming about 1L per 1000km of oil
Pcv valve was just replaced but still seems to be burning oil and high crankcase pressure.
Any ideas what it could be.
Please dont say rings, valves and gasket lol
I today passed on a perfect 77 240d with 107k miles because of this. I’ve been looking for awhile. I am so pissed. Now if I go back I’ll look like a retard. Tried on my 2017 and does the same thing!
Adjust the valves, and if it fires up cold, it's got compression. I was told years ago by a very astute MB diesel scholar (whose initials happened to be MB) that compression test results can be erroneous. Cold start is the best test of compression according to him. Cheers!
I had w115 200D with cracs in pistons (I could see the sky looking through them) and it fired up. Motor can be dead long before, it would not fire up. It did take 25l of oil in 100km but it fired up - took long time to crank it, but it fired up.
@@shmeleu I should have said fires up right away. Nearly instantly.
@@Rick_Kn you're absolutely right.
Yes, and CHANGE your FUSES!
love it
Great video,are the 190 d good cars they were made in the late 80s till 1992
yes they are
You're right.
I've had more than 1 person tell me those cars were supposed to burn oil. Even 1 or 2 say that 1 full quart ever 500 is normal. One of them has a 240D w/ stick-shift and about 230K original miles and was adding a quart ever time he filled it with diesel, and said that's normal once broke in. Weird. I kind of knew not to believe that. I already knew someone who had an '80 300D Diesel with 115K on it and was having to add a quart every 1,000 miles, not 500. And he was planning on having it rebuilt in another 30K. And I had a '77 300D that I had overhauled at 190K because it was in its last leg. 90,000 miles later, it started to smoke more than before. Still wasn't consuming any oil. Then it was slow to start until I'd stop and start again. Then it would start right up. My regular mechanic had it sent to an actual German car mechanic who checked and said compression is gone, rings are shot, junk it and get myself another car. Didn't matter if still no oil consumption. Could there have be any worse news? He said to me, "you put 90,000 miles on it". And I'm like "yeah I did and I expected over 3 times that." 5,000 miles later, sure enough, excessive blow by was discovered . Motor was taken out, rings were found to be shrunk. And parts to receive to re-build it included another set of the same exact rings as the ones that didn't hold up. Bearing themselves had minimal wear, no oil consumption for all that time, and I was told that didn't even matter.
This is an interesting story.
Most Mercedesdo tend to run a lot longer. I would say that there was some kind of underlying machining error in the engine work rather than a problem with the engine itself. We see this quite a bit as well. So many of these engines rebuilt and properly. The 77 is particularly sensitive. Did you install new Pistons with your rebuild? Off in this is the secret to longevity. But I digress, you pointed out something very interesting. That the oil scraper rain can still be in perfect working order while the rest of the rings are totally shot.the future, it's prudent to address piston and liner issues rather than just replacing rings
A quart every 250 to 500 miles is really high. 378000 miles, my 300D uses a quart every 2500 miled
@@thisisnightshop2037 Well, all that was over 20 years ago now. My dad did suggest that there was definitely some machine or engineering error involved. The place was an independent Mercedes garage with a mess of stuff lying around (inside and outside) including a half dozen different Mercedes gas engines sitting out side. It was a $4,000 plus a few $ job. And he thinks the factory swap right at the dealership would've been much better. But He's always been thinking that some wrong materials were used. But the story had a very disturbing ending.
@@thisisnightshop2037 I agree. 1 quart of oil every 500 to 1,000 miles on a gas engine very much indicates it's in its last leg. I cannot possibly see how it could a whole lot different with a diesel engine. They can't be that radically different.
"Blowby" is used by buyers of crappy cars to tell the sellers "blow" me and good "bye".
I thought the recommended oil change interval for a 617 was 5K. I'm pretty sure I read that in a manual somewhere.
Sure, when they were still young. As they rack up a lot of miles, I change them every 3000. Better too often than not often enough is the way I figure it.
@@gravytrain416 Too much detergent might not be the greatest either, though. With a full synthetic (rated for 7500 miles), I don't worry that much about letting it get between 4 and 5.
...but I haven't put that many miles on it in a few years since I don't drive it much and the yearly change happens according to the calendar.
But the oil change question interests me. I wonder if you can change it too often, considering the additives.
@@Greg042869 Fresh oil will always have more protection than an older oil. I also try to change every 3000 miles because its got 180,000 miles on it.
@@tyd2281 I'm concerned about the detergent element of the additive package.
@@Greg042869 , I don't use synthetic oil in the older cars myself. I had a 1984 300SD which I finally stopped driving at 752K miles. Original engine lasted 703K before anything major was done to it. Always did oil changes at 3K miles with Castrol 15W40. Never had an oil usage problem. Did good for me. Good question though.
still worth a few extra $$ off the sellers asking price :)
Great information! I enjoy watching and learning from you. Hopefully I’m going to be picking up a ‘69 280SE soon!! Opinions on that?
Sorry for the late response period with those cards you should be checking for worn valve guides , blue smoke on deceleration
Good video. having only owned gas engine mercedes I had just assumed that Mercedessouce was correct on this.
I like kent and think he's good but not as good as our friend here!
Say, did you say in one of your replies to me that you have noticed some engines not rebuilt properly? The '77 300D must be sensitive.
rebuilding one of these engines is difficult. the biggest mistake most machinists make is that they don't replace the cylinder Liners and pistons .you have to do that to get the best results
I'm an absolute fan of mobil 1 oil in all mbs. Within 20,000 miles many issues start to disappear. Also, an Italian tune up does wonders. But yea, the so called blow by test isnt really a valid test.
Isn’t the definitive test a compression check ?
yes and leak down
I had that same car for 200k miles. if your air filter is oiling up, then remove it. clean out the housing perfectly. get a washable cone air filter and attach it to the air intake hose. you will see a huge improvement. I was changing my oil every 1000 miles because oil was free to me when working at the dealership. for most of those miles i ran 75%used atf to 25% diesel. the 617 runs better on atf than diesel. I wish I had installed a charge air cooler and modern turbo. i would prefer a w201 with a diesel. can't find them.
ATF causes excessive carbon build-up in the motor. Just because it runs more quietly doesn't mean it's better . a good diesel has loud combustion knock at idle.
@@thisisnightshop2037 bs. i know because I did it and there was no carbon build up
also, no modern turbo lasts for the as many miles as the garret or kkk used on these cars. Longevity is rule number one.
@@thisisnightshop2037 i could care less what you do. I know it works very well. also I am a Mercedes Mechanic. atf runs very smooth in the om617.
@@narcissistinjurygiver2932 why are you so angry? I just asked for proof.
Why not just use a glove??
Good thing you're a car mechanic and not an audio engineer. Can't anyone hear the crazy amount of distortion in the music during the end credits?
gotham61 jump on Patreon and help make the quality of the videos better.
Quality has improved along the way.
it was a windy day. focus on the information.
Disliked. Vales have no affect on blow by. Blow by is caused by compressed gasses leaking through the piston rings.
how do you dial in the Alda??
You turn the screw out slowly until you feel you reached the best acceleration from 0
@@thisisnightshop2037 if I turn the screw the opposite way will MPG go up because less fuel?