Got a quick 300SDL oil pressure question. - PeachParts Mercedes-Benz Forum

LUVMBDiesels · #1 03-31-2008, 12:27 PM

In my 'new' '86 SDL, the oil pressure never gets above 3bar. It starts cold at 3, idles warm at around 2+ then when I press the accelerator comes up to around 3, maybe just a hair lower than the number. This happens under load at all RPMs off idle.

I know from experience with my 300SD that the 617 should bring the oil pressure to 3+ at any RPM over 1800. Is it the same on the 603? I just changed the oil from whatever the PO had in it to Rotella synthetic 5w40 but the pressure is the same.

Could it be the sender or gauge reading low? what voltage should the sender be putting out at 2bar, 3bar and over?

Thanks!

#2 03-31-2008, 12:39 PM

Should be the same pressure. Your sender could be faulty or a bad connection between the sender and gauge.

LUVMBDiesels · #3 03-31-2008, 01:06 PM

Quote:

Originally Posted by ForcedInduction

Should be the same pressure. Your sender could be faulty or a bad connection between the sender and gauge.

I am thinking the same thing. I would like to know what voltage the sender is supposed to be putting out so I can test it. I guess the best thing to do is to get a mechanical gauge and connect it to the port the sender goes into. If it reads OK, then I know it is not the engine.

BTW, would the oil pressure, gas, and temp gauges from a 300SD work in a SDL?
I am thinking they should be the same gauges, but you never know...

Diesel911 · #4 03-31-2008, 08:57 PM

Quote:

Originally Posted by LUVMBDiesels

I am thinking the same thing. I would like to know what voltage the sender is supposed to be putting out so I can test it. I guess the best thing to do is to get a mechanical gauge and connect it to the port the sender goes into. If it reads OK, then I know it is not the engine.

BTW, would the oil pressure, gas, and temp gauges from a 300SD work in a SDL?
I am thinking they should be the same gauges, but you never know...

Mechanical gauge check is a better idea since the voltage going through the sending unit varies with the enine oil pressure.

Hatterasguy · #5 03-31-2008, 09:00 PM

Mine and my brokers does the same thing, I think thats just how the guage is set.

bustedbenz · #6 03-31-2008, 01:18 PM

Quote:

Originally Posted by LUVMBDiesels

In my 'new' '86 SDL, the oil pressure never gets above 3bar. It starts cold at 3, idles warm at around 2+ then when I press the accelerator comes up to around 3, maybe just a hair lower than the number. This happens under load at all RPMs off idle.

I know from experience with my 300SD that the 617 should bring the oil pressure to 3+ at any RPM over 1800. Is it the same on the 603? I just changed the oil from whatever the PO had in it to Rotella synthetic 5w40 but the pressure is the same.

Could it be the sender or gauge reading low? what voltage should the sender be putting out at 2bar, 3bar and over?

Thanks!

Come again?

3 bar is the top end of the gauge reading in any case..... you're saying it's essentially maxing out the gauge... what more do you want?

Not trying to sound smart by any means, I just don't quite understand what the problem is here.

LUVMBDiesels · #7 03-31-2008, 01:25 PM

Quote:

Originally Posted by bustedbenz

Come again?

3 bar is the top end of the gauge reading in any case..... you're saying it's essentially maxing out the gauge... what more do you want?

Not trying to sound smart by any means, I just don't quite understand what the problem is here.

On the 300SD, the needle would go past the 3 when the engine went over 1800RPM. From what I read on the forum, that is normal behavior.

On the 300SDL the needle stops just below the 3. I am concerned that the pressure is either too low or the gauge is not working correctly.

I just got the car and have no history in it as to if the needle used to go past the 3 or not...

What I am wondering about is if this is normal SDL behavior or if I need to correct anything.

bustedbenz · #8 03-31-2008, 01:31 PM

Quote:

Originally Posted by LUVMBDiesels

On the 300SD, the needle would go past the 3 when the engine went over 1800RPM. From what I read on the forum, that is normal behavior.

On the 300SDL the needle stops just below the 3. I am concerned that the pressure is either too low or the gauge is not working correctly.

I just got the car and have no history in it as to if the needle used to go past the 3 or not...

What I am wondering about is if this is normal SDL behavior or if I need to correct anything.

Based only on my car, I think it's normal. I think the gauge must have a mechanical stop of some sort to make it look less alarming (There are people who would find a gauge higher than its indicator scale alarming). Mine stops right on the 3.

As long as it jumps up when you leave idle, I think it's fine.

Brian Carlton · #9 03-31-2008, 01:33 PM

Quote:

Originally Posted by LUVMBDiesels

On the 300SDL the needle stops just below the 3. I am concerned that the pressure is either too low or the gauge is not working correctly.

I'm sure it's just the idiosyncrasy of that specific gauge. The hard stop for the gauge is just slightly below the 3 bar setting.

daw_two · #10 03-31-2008, 01:49 PM

Quote:

Originally Posted by LUVMBDiesels

On the 300SD, the needle would go past the 3 when the engine went over 1800RPM. From what I read on the forum, that is normal behavior.

On the 300SDL the needle stops just below the 3. I am concerned that the pressure is either too low or the gauge is not working correctly.

I just got the car and have no history in it as to if the needle used to go past the 3 or not...

What I am wondering about is if this is normal SDL behavior or if I need to correct anything.

Sounds like you have a BAD Engine and ought to get rid of that baby as fast as you can. I have a place to store it while I look for a replacement engine. I'll give you $600 for it.

LUVMBDiesels · #11 04-01-2008, 10:35 AM

Quote:

Originally Posted by daw_two

Sounds like you have a BAD Engine and ought to get rid of that baby as fast as you can. I have a place to store it while I look for a replacement engine. I'll give you $600 for it.

What $600 for the 'bad' engine? I have a 300SD with one I will give you for $500

You pay for the bad engine and the rest of the car is FREE!!!

Sure make fun of me.... I just never had a 603 motor and I worry about Rudy's health...

LUVMBDiesels · #12 04-01-2008, 10:38 AM

BTW...
Thanks for the replies. I will check the gauge closely for the stop and see it the needle is hitting it. I am not too worried since the pressure at idle is 2+ and it does shoot right up to -almost- 3, but being used to the SD, I am used to seeing the gauge way past 3

daw_two · #13 04-01-2008, 05:04 PM

Quote:

Originally Posted by LUVMBDiesels

What $600 for the 'bad' engine? I have a 300SD with one I will give you for $500

You pay for the bad engine and the rest of the car is FREE!!!

Sure make fun of me.... I just never had a 603 motor and I worry about Rudy's health...

Rudy? Is that her name? My "new" 300SDL is named Coda. Undriveable cars have to be in the same city for me to get interested in them. If I am able to save every old Mercedes diesel I see parked......I'll be busy for the next 3-5 years. This town is full of them.

P.E.Haiges · #14 04-01-2008, 11:43 AM

LUVMB,

There is an over-pressure valve in the engine that opens about 3 Bar to relieve the pressure.

Remember the oil pump is a constant flow (gear) pump and pumps oil proportional to its speed. Oil pressure is determined by the viscosity of the oil and resistance of the oil going thru the engine. This why oil pressure is higher in a cold engine (higher oil viscosity) and worn engines have lower oil pressure.

I don't see any problem with your engine.

P E H