Losing oil pressure when running hot

Gunnar A while back I was considering buying a 92 300E that would lose oil pressure as soon as it got warm. I had mechanic confirm that it was a faulty sending unit by removing it and installing a mechanical test guage. That cost me $50.00 but I didn't buy the car becasue the price was too high. You may have a bad sending unit.

I have w140 with almost the same behavior. I haven't worried too much yet, but should I?

Jens

You've done all the right things - but one.

engine has an unknown mileage - probably around 300-400 kkm (yet you're) doing some kick downs on a hot engine on my way home.

That's like asking your grandmother to play rugby or soccer, not age appropriate.

This is an old engine whose best days are long gone, its low oil pressure at idle isn't good but it's OK if you don't idle it for long periods. Yes, the bearings are worn, the oil pump is worn etc. and you could use even thicker oil (20 - 50) the next time. Drive it conservatively and the engine will be OK.

You can easily check the oil cooler by driving the car for some time and feeling if the oil cooler is hot (OK) or not (not working).

I believe there's a thermostat for the oil cooler - about 200 degrees F.

- that's probably located below the oil filter.

Thanks for your excellent answers.

I don't kickdown much, but did it to see what would happen. I'll be nice to it. (Is kickdown worse on a hot engine or a cold engine?) Maybe I'll even get around to mount the calix engine heater I've acquired before the winter sets in... :-)

About the oil cooler - I'll check it the next time I have a longer trip.

Best Gunnar

T.G. Lambach wrote:

e oil pump is worn etc. and you

Cold.

Being hard on a cold motor is never a good idea, do you not think?

DAS

For direct contact replace nospam with schmetterling

These are both the same viscosity when hot. Try running something thicker.

Like Mobil 1 15/50 or good old 20/50

Probably a main bearing is worn and losing some oil pressure.

Marty

I do! I just got confused.

Gunnar

Oh, good... after all, we wouldn't want to hammer a cold engine in a Frederikssund winter... :-)

DAS

For direct contact replace nospam with schmetterling

I'm with T.G. You're asking a lot from a tired engine. I like the 15-40 oil since it is rated for diesel service limits. I use it in my tractor, pickup truck and two MB diesels. The 20-50 might be okay and you could add something like the old STP or something of the same caliber to increase viscosity. I would also do like a previous posted suggested and check the oil pressure with a separate gauge of known quality. I had low oil pressure on my Ford pickup with only 70k on a complete rebuild. Put in a new oil pump and things came right back to normal. Don't know how hard it is to replace the oil pump on your engine but if it can be done without too much trouble I'd try that before getting too far into the problem. That move never seems to hurt a tired engine.