Oil Cooler Problems - PeachParts Mercedes-Benz Forum

RUYSENAARS · #1 10-12-2004, 05:06 PM

Ok people, I have a 83 300d, oil cooler is always cold. I have taken out the oil thermostat, still no flow?? Any ideas, I think this is causing my low oil pressure when it's hot. The lines are clean, and flushed out the cooler itself, it did smell like old oil. I have changed my oil pump, installed new rod, and main bearings, still no change. What next?? Thanks ahead of time!

#2 10-12-2004, 06:47 PM

Just have your power steering belt cut through one of your oil lines due to bad motor mounts and you will find out if oil is going through those tubes...
it worked for me

Honestly though, that is quite the pickle. Tried loosening one of the lines while running to see what is going on inside'?

#3 10-13-2004, 03:25 PM

I will be surprised if this has anything to do with your oil pressure problem. You said that you still had no flow with the thermostat out. How did you check for flow?

When you replaced engine bearings did you mic the crankshaft to ensure that you do not have excessive clearance? Are your camshaft bearings tight?

You say you have low oil pressure. What are you calling low?

Good luck,

RUYSENAARS · #4 10-13-2004, 03:48 PM

Ok first of all oil pressure when at normal opperation temp 85c at idle is .3bar. which is below standards. When we changed bearings, no apparent wear in old ones, checked the crank, no wear. The oil pressure doesn't seem to drop substantially until over 80c. On others that we have driven the oil cooler is extremely hot, and the temp gauge reads 80c, with normal oil pressure, above one bar. This is crazy.

By the way, I have asked variations of this question over the past year or so, no the suggestions have been tried to no avail? please brain storm!

Wasuchi · #5 10-13-2004, 04:19 PM

Have you eliminated the gauge as the source of the problem? It may read 3 bars at speed even if it is way off.... just throwing out ideas. I can't figure why your oil cooler wouldn't get hot after driving for a while although I don't see how some blockage there would make your pressure lower.

RUYSENAARS · #6 10-13-2004, 04:32 PM

Well first, I have put another gauge on it, same pressure. Second, I am not looking at it as no flow no pressure, but rather, no flow, no cooling of oil, therefore greater thinning of oil, thus produceing lower pressure. Follow me? I am thinking this because I have a Diesel tractor, and looking at the pressure the hotter the engine oil the lower the oil pressure. What you think?

tomm9298 · #7 10-13-2004, 04:44 PM

I've looked through my parts guide and see no mention of an oil thermostat. Where is this located? My pressure when cold pegs at 3 idle or under load. When at temp it is 1.5 at idle and pegged at 3 under load. I have seen other threads refering to this as normal. Please let me know.

RUYSENAARS · #8 10-13-2004, 05:10 PM

The oil Thermostat is in the oil filter housing. I have taken it completely out, still no flow, HMMM! In your diagram it should have an oil flow throught the oil filter housing, there are a series of pressure "regulators??", springs, but I have no idea how to test them to see if they open, and/or seal the right way. I hope I am describeing this accurately, and some what clearly.

tomm9298 · #9 10-13-2004, 06:07 PM

Does your oil filter stem have the correct washers/seals? Should be 2 of them.

tomm9298 · #10 10-13-2004, 06:26 PM

Here is a link, if you need it. Shows removal/install of oil thermostat. You are correct, when engine is at operating temp, oil cooler should be warm to the touch. If not replace thermostat. However, I cannot find one for sale at any parts supplier on the net. Let me know.

http://skinnerbox.steaky.org/Service/W123/Index/617T/18Lubrication.htm

RUYSENAARS · #11 10-14-2004, 10:47 AM

Yeah, I know where it is, I have a new one. The funny thing is, I took the thermostat OUT all together. So it shouldn't matter what temperature it is it should run through it regardles. That is what I don't understand. So something perhaps in the oil filter housing is preventing the flow into the cooler?
By the way, I went to the dealer to buy one. Not expensive under $10.00
THIS IS GIVING ME A HEADACHE!! HAHA! THANKS FOR THE INPUT!

tomm9298 · #12 10-14-2004, 03:39 PM

Must be dealer item only. Have you cracked open a line to see if there is flow? Should spray out!!

punky · #13 10-14-2004, 04:58 PM

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I'm probably wrong being an amatuer but don't some Euro versions delete the oil cooler, if so, that would rule out your position of no cooler flow at hot temps= low pressure.

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True, so you've cured your pressure problem. Again, cooler out of the picture.

I believe someone posted a couple of weeks ago(maybe it was another forum) that the oil temp needs to get very hot before cooler kicks in, i.e., very long highway drive.

tomm9298 · #14 10-14-2004, 06:53 PM

In the MB manual it shows the thermostat in the oil filter resevoir. Dealer item only!!! It does exist.

TonyFromWestOz · #15 10-15-2004, 10:57 AM

is set at 90'C, so the engine must be above NORMAL operating temperature for it to open.