Remnik

I have a 2005 Freightliner M2 with a C-9 that has been having unusually high oil pressure when first started in the mornings. The truck is fairly new to me but I don't remember ever seeing more than 50-55 psi on start up but recently it has been at about 75-80. If I rev it up a little I can peg the gauge at 100. Once it's fully warmed up it's normal at about 40 psi when running down the highway.

I took it into a Cat dealer and they checked the oil pressure sensor and it was ok, the laptop hooked up to the truck was reading 112psi at about 1600 rpm. The service manager said they would have to replace the oil pump. So, 1200 plus dollars later and the pressure is still the same. They wrote on the repair ticket that it was at 76psi at 1200 rpm all ok.

In the Cat manual it says the pressure should be 30-70 at rated speed (which is 2100rpm I think) so 76 at only 1200 is way too high right?

I've called a couple other places that work on Cats and they say not to worry about high oil pressure that cats run kinda high. But, I'm not always going to be able to warm the truck up before driving and when the weather is colder it's only going to be worse.

So, what do you all think?

BTW, the mechanic said that he couldn't get the oil pan all the way off and had to replace the pump with it hanging there. Is this even possible?

Tedonlin150

I rebulilt a C9 at school last spring. There is no way anyone could replace the oil pump without dropping th oil pan all the way

Hvytrkmech

Please tell me the tech verified the electronic readings with a manual test gauge????

Remnik

This is what I thought, it seems like this would be impossible, but I've also heard from a pretty good truck mechanic that it can be done. So, I'm not sure what to think.

Remnik

I wish I could say yes but all I saw him do was hook up a laptop under the dash and read the pressure from there.

I may try to hook up a manual pressure gauge this weekend.

PoorMansCat

do as others have suggested, hook up a manual gauge and verify your dash gauge. Remember that at different points on the engine, the pressure will vary... if possible, purchase a STOR "T" and take the reading from where the engine oil pressure is located. (apples to apples)
Not sure about OTR, but I would speculate that your gauges are simply reading off the CAN bus, so in essence, they are reading from the CAT OP Sensor.
If the oil pressure is truly high, then yse, drop the pan and replace the engine oil pump.. If not, replace the oil pressure sensor.
Sometimes the OP sensor can get out of calibration so a tech not paying attention may just look for fault codes and not actually look at the status screen and verify the sensor reading.. there is no way to calibrate a faulty sensor, just replace it.

Remnik

I never got to hook up a manual gauge but I ended up taking the truck to another Cat service center because Cat was footing the bill to replace the oil filter housing. After replacing it, the oil pressure is still high so we're back to square one I guess.

I'll have to wait to hear what Cat corporate is willing to do now on this.

pokapotato

Can you tell me the serial number prefix?