603 Oil Guage High after Oil Change - PeachParts Mercedes-Benz Forum

86-300sdl · #1 10-02-2015, 03:22 PM

Normally after I do an oil change my 603 the oil gauge sits around 2 on the gauge at idle and pegs under throttle.

Now it's sitting close to the 3 at idle well after warm up.

Could this be telling me my aftermarket oil filter may be messed up and not allowing pressure to drop at idle? I'm not sure where the filter sits in regards to oil return journals and oil pressure sensor.

Same oil as always, weather the same, etc, etc

mannys9130 · #2 10-02-2015, 06:14 PM

Did you change the two orings at the bottom of the housing cap stem?

97 SL320 · #3 10-02-2015, 07:58 PM

On most cars in general ( every one I've worked, on that is in the thousands ) , the pressure sender is after the filter.

Elevated idle , oil on the thicker side of the scale even though it is the same weight , pressure sender / gauge starting to fail. .

mannys9130 · #4 10-02-2015, 08:22 PM

Right. Since pressure is resistance to flow, something has changed where the flow of oil is less than before. That's why I'm curious about the orings on the cap stem. When old and hard, they leak. The leak allows pressurized oil to escape, which reduces the resistance to flow and therefore oil pressure. New orings will seal correctly and won't allow leakage to reduce oil pressure.

Mxfrank · #5 10-02-2015, 08:38 PM

The oil sender is located on the side of the oil filter housing. This measures the oil pressure after the pump but BEFORE the filter, maybe unique to the diesels. That suggests that either the filter is clogged or otherwise obstructing flow, or the center tube is plugged. Hopefully, nothing fell down into the oil galleries or relief valve. I'm attaching diagrams of the filter housing in my 190DT, all 60x housing are of similar construction. Notice the flow pattern

The logical thing to do is to replace the filter again, inspect the center tube, and replace those o-rings, too. I would use a can of carb spray to clean the inside of the center tube, including the little holes that carry bypass flow. Inspect the inside of the housing for debris. Put it back together and see what you have.

86-300sdl · #6 10-03-2015, 07:45 AM

Thank you for the feed back....In my 50 years of wrenching on my cars I've never said "wow my oil pressure seems kind of high" LOL

its a Purolator filter...could not find anything else on oil change day. Poor planning I know.

Rubber seals are about 15,000 miles old.

I'll head down to the dealer this morning for new filter shaft seals & filter.

No one else I know within 40 miles has the mann filter. It's worth the extra nickel (or ten) for the correct gear.

I've run purolators in the past when in a pinch with no problems.

Thanks for the system flow location of the pressure sensor. That is a big help.

I'll report the back with the results.

Mxfrank · #7 10-03-2015, 09:20 AM

Fwiw, Ive never had a problem with Purolator. My favorite filter for the diesel is Fram, their filter for this application is surprisingly well constructed.

pmckechnie · #8 10-03-2015, 09:46 AM

I have seen this problem many times over the years. Do a simple test, turn the ignition on but don't start the engine. If the gauge reads 3 bar then you have an electrical problem, possibly the sending unit or its connection. If the gauge reads 0 and goes to 3 as soon as the engine is started (after it is warmed up) it still could be the sending unit. My first guess is the wire on the sending unit was bumped and lost its connection when the oil was changed.

PaulM

86-300sdl · #9 10-03-2015, 01:39 PM

Just put a new filter on from the dealer ($4 more than Pep B's Purolator...no biggie).

Replaced the two filter canister shaft rubber seal rings.

Bingo...lol......Oil gauge needle pegs at about 900 rpm and drops to the 2 mark at idle in keeping with all previous change observations.

So maybe there was something with the oil filter? Seal rings seemed fairly fresh...I think I had about 15k miles on them. Swapped them out anyway.

This was about the 95th oil change I've done on the car (416K miles). Run both syn and dino oils and various wt's. Seen some small variances in idle oil pressure due to oil type, oil temperature etc. But never a pegged needle at idle.

As always I appreciate all your input!

P.S. also going to clean the sensor connector (good tip)..thx

86-300sdl · #10 10-03-2015, 01:43 PM

Quote:

Originally Posted by pmckechnie

I have seen this problem many times over the years. Do a simple test, turn the ignition on but don't start the engine. If the gauge reads 3 bar then you have an electrical problem, possibly the sending unit or its connection. If the gauge reads 0 and goes to 3 as soon as the engine is started (after it is warmed up) it still could be the sending unit. My first guess is the wire on the sending unit was bumped and lost its connection when the oil was changed.

PaulM

Thanks Paul

Gauge read 0 with ignition turned on (both position 1 & 2)...Great tip!

babymog · #11 10-03-2015, 09:32 AM

There are threads dedicated to these filters.

I buy mine at O'Rieley, they stock the Wix which has been a good filter, ... from previous threads comparing the country manufactured and the pictures of the filters much has been written about who makes filters for who (especially in the US market for obsolete applications).

As far as higher pressure, you will notice that at idle even with hot oil the gauge seems to stop dropping around 1.5bar, which is where the piston oil squirters close and all oil flow is routed to the bearings. When you first start it takes a while for warm oil to get to the piston squirters and can show elevated pressure for a while on the first run-up.

Every 60x engine I've had pegs the gauge above about 800rpm or so even warm, but pegged at idle isn't normal for warm oil. One caveat though: I've never run regular dino oil so I can't comment on whether it behaves differently (although thicker when cold and thinner when warm).

97 SL320 · #12 10-03-2015, 08:34 PM

Given you have a lot of history with this car, a diagram shows that the sender is pre filter and changing the filter brought readings back to normal, the filter was the problem. ( restrictive media , not enough surface area )

A leaking o ring on the filter would only cause the filter to bypass and not raise pressure.

Having a pressure sender pre filter isn't common. You might use this to your advantage though. Adding a 2nd gauge post filter would give you pressure drop across the filter and indicate when it needs changed. A more direct route would be to install a pressure differential gauge, this would read pre and post filter giving you a direct reading .