Not sure how long you've been plagued with temp problems, but make sure the cap is screwed on properly. There are notches along the bottom of the cap and around the reservoir spout...I have at least once, put the cap back on and not screwed it tightly beyond the first set of notches. The result was higher than expected temps and boiling over after driving.

Go ahead and replace the cap first...cheap insurance.

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2009 ML350 (106K) - Family vehicle
2001 CLK430 Cabriolet (80K) - Wife's car
2005 BMW 645CI (138K) - My daily driver
2016 Mustang (32K) - Daughter's car

I had the same problem. New thermostat and two the expansion tank caps later, the operating temperature is much more consistent.

I bought the 1.2 bar cap first but it did not seem to work well - thus switching to 1.4 bar one (superceded replacement part)

Frank.

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'86 560SEL | Silver Ext. / Blue Int. | 201K miles (Apr. 05) | 204K miles (Feb. 06)

Replace the cap and flush the fluid.

I have the perfect oil for you! Castrol High mileage 20w-50. I am pretty sure I just saw this stuff at Autozone. I used the 10w30 in my Toyota for a few years and it works as advertised it softens old seals and makes them seal better.


Also this time around use a better quality filter it will probably bump your oil pressure up a bit. Head for the dealer and spring for an OE filter.

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2016 Corvette Stingray 2LT
1969 280SE
2023 Ram 1500
2007 Tiara 3200

you said the pressure drops when you stop. is your oil level correct. the oil pressure dropping to a very low reading and coming right back up could be from the oil rushing away from the pickup if it is low. and if you are stopping very hard.

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.

Yeah - I checked it and it is full. The PO had let the oil go well beyond the time to change. The filter was so old it had a big hole in it that was not supposed to be there. I put on a cheap filter- which may be the problem. Perhaps like Hattaras said, if I use a genuine MB filter it will improve? Maybe I should also go with the high mileage 20W-50 oil on the next change....

Thanks again.

about the filter affecting oil pr. i dont understand how unless it actually presented too much resistance to flow.

the heavier oil is a good idea. it should bring it up a little. i would also prob avoid the synthetic in this case since it tends to be thinner.

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.