Öldruck

[Gregorix]

Beim Diesel von meinem Cousin, baut sich beim Starten der Öldruck manchmal sehr spät auf.
Das Problem tritt nur gelegentlich auf.
Nach bisherigen Beobachtungen besonders, wenn das Auto bergauf steht.
Erst ist lange kein Druck da, dann baut er sich normal auf.
Öl wurde gegen ein dünnflüssigeres getauscht, hat das Problem aber nicht behoben.
Öldruck im Betrieb ist ganz normal.

Was könnte die Ursache sein?
LG, Gregor

[Profpinz]

Everything I've ever read on the various VW, diesel or D24T Forums suggest that this is a common problem with this motor.
Their have been various ideas put forward as to the cause, but it seems that long, large diameter pickup tube may be part of the problem.

Here is an extract from the UK Volvo Forum
https://www.volvoclub.org.uk/faq/EngineDiesel.html

"Synthetic Highly Recommended. [Warren Erickson] While many people use normal 15W-40 dino oil in their D24 engines, you might consider a synthetic oil due to a design flaw leading to low startup oil pressure. I just finished a rebuild on a spare D24T that I intend to use as a backup for my 760. After finishing the rebuild, I did a compression check. I previously screwed a gauge in place of the switch to monitor oil pressure. During the compression procedure I was monitoring the gauge, NO oil pressure. I then decided to bench run this engine. I made it a point to monitor oil pressure. It came up after a delay and was where it should be.

But the delay, and a previous note from a friend that showed no oil pressure for over three minutes if the engine is standing on an incline, pointed out that the D24 has a rather strange oiling system. It has an oil pump with a long suction tube. The pump is mounted in front of #1 main bearing and the oil pickup screen is way down in the sump by #5 main bearing. This suction tube is close to 36" long and has an inside diameter of approx. 3/4". I'm not a mathematician, but it's obvious there's a lot of volume to be filled before the pump ever gets primed. And you'd better have a good pump to pull a suction. To make matters worse there is approx. 6" between the level of the pump and the oil level. That's a considerable suction head for a heavy liquid. Most engines that I have rebuilt have the pump located close to oil level or submerged.

Now when the engine was new and pump clearances were tight, oil delivery was probably was not a problem. After thousands of miles, clearances increase and pickup time increases. Multiply these dry starts by thousands during the engine's life and you get reduced engine life - one of the complaints of this engine - despite its robust construction.

I could never figure out why synthetic oil worked so well on these engines. After all truck drivers were using the likes of Rotella Dino 15W-40, and getting 500,000 miles without a rebuild. Well it all makes sense now: synthetic oil's superior film strength and lower viscosity when cold. It's able to handle dry starts better. Hence, longer engine life in our D24's when using synthetic oil.

Now this does not correct the original problem; it's only a good a work around. Probably the best thing one could do is replace the pump during a rebuild and switch to synthetic. I'm afraid even a new pump will not completely alleviate what is in essence a design flaw and that only using a synthetic will keep your problems at a minimum ".

[Gregorix]

Hi Peter,
Tank you for this excursion to the volvo forum.
I knew about this speciality in the oiling System of this engine, therefore we changed the oil to synthetic 10w40.
But the symthom occures again today morning. The car was inclined, but the weather is relatively Hot, soI was very curious if ther coul be som other problems.
Surprisingly I had never any such problems with my own 718.
Which is a P90 compared to the P80 from my Cousin. Did they make any changes in the oilimgsystem during the production?
My P90 was running about 170000 km, the P80 has only ca.60000 km, so the wear cannot be the only reason I guess?
Kind regards, Gregor

[Profpinz]

G'Day Gregor, Their is an updated/new oil pump shown for the P93, but I'm not sure what the difference is to the P80-P90 unit, or whether it can be retrofitted to earlier version motors.
http://www.puch.at/en/spare-parts/pinzg ... /oil-pump/
As there are so few TD's in Australia, I haven't had the option to strip down and investigate the differences between the P93, P90 and P80 units......I daresay someone like Wolfgang F would be able to tell you.
Regards from Australia.