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  #1  
Old 11-17-2006, 06:19 PM
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low oil pressure question

I recently bought a 85 300 TDT (california version.) When I bought it the oil pressure guage line was cut but it wasn't making any terrible noises so I assumed the pressure was ok. When I replaced it this week I noticed after the engine got to operating temp. (about 90F) the pressure would sometimes drop to "0" at idle and "1-2" at low rpms but go back up to 3 bar at higher rpms. Is there a pressure sensor on this version that might be bad?

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Old 11-17-2006, 06:53 PM
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The problem is that it's a mechanical gauge. There is no sending unit. The oil is sent directly to the instrument cluster.

You mentioned that the line was cut. How did you operate the vehicle under this condition? Oil would normally be everywhere.

What viscosity and type of oil are you running in it?
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Old 11-17-2006, 07:00 PM
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Thanks for the response, Brian.

There was a plug in the filter housing and I am using Rotella 15/40.
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Old 11-17-2006, 07:01 PM
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Quote:
Originally Posted by bottom feeder View Post
Thanks for the response, Brian.

There was a plug in the filter housing and I am using Rotella 15/40.
Your only hope is that the gauge is in error..........but........it's a longshot.

How's the blowby?
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  #5  
Old 11-17-2006, 07:08 PM
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There's no blowby at all. If not the gauge what do you think it might be?
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Old 11-17-2006, 07:10 PM
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Quote:
Originally Posted by bottom feeder View Post
There's no blowby at all. If not the gauge what do you think it might be?
If the engine is in good shape, it's the gauge.

If the engine is not in good shape, the oil pressure at idle can get below 7 psi. This is not the best of circumstances.

Without any blowby, I'd be more inclined to disbelieve the gauge. See if you can hook up a standard oil pressure gauge outside the vehicle and get a good number from it.
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Old 11-17-2006, 07:16 PM
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OK, thanks very much. I will try that.
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  #8  
Old 11-17-2006, 07:41 PM
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the cut line is a bad thing in two ways.

one they may have cut it to disguise the low oil pressure.

two if the line failed for some obscure reason, it could have run it dry causing the low oil pressure from bad bearings.

hope brian is right.

tom w
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Old 11-17-2006, 08:12 PM
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Tom,

Thanks for the reply. I must admit that I'm afraid it might be something serious like the bearings. What would be the signs of bad bearings?

Last edited by bottom feeder; 11-17-2006 at 08:28 PM.
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Old 11-17-2006, 08:23 PM
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Tom,

Thanks for the reply. What would be the signs of bad bearings?
Low oil pressure is the first possible indication.

If the clearance gets larger, you'll hear them knock. Sounds like a dull hammer tapping on the bottom end of the engine.

Get a proper reading for oil pressure first, before worrying about the problem that may not exist.
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  #11  
Old 11-17-2006, 08:33 PM
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There is a sound similar to that at idle sometimes, but is not heard at RPMs higher than idle. But first I'll do the oil pressure check. But I have a sinking feeling on this Friday night. I think it's time for a beer.
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  #12  
Old 11-17-2006, 09:40 PM
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from the manual on my 93 300D:
"The oil pressure at idle speed may drop to 4.4 psi (0.3 bar) if the engine is at operating temperature. This will not jeopardize operational reliability"

"Pressure must, however, rise immedlately upon acceleration"

p67.

If you can't stand low pressure, run 30 weight year round. that'll peg the needle...
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  #13  
Old 11-18-2006, 12:37 AM
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Get another guage on there and either confirm or disprove the reading. Min spec at hot idle is .3 bar.

If the guage is accurite don't worry you can ebay it!
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  #14  
Old 11-18-2006, 01:36 AM
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oil pressure

at risk of being banned by the purists let me state that all of my diesel engines have a quart or more of lucas oil treatment in them and straight 40 weight oil
The boat engine (Volvo 70E 300hp) was suppose to need a rebuilt 4 years ago and 7500 hours of running ago The Volvo holds 7 gallons of oil of which 1 gal is lucas @1700 rpm this 1986 engine with over 30000 hours of running holds 55 lbs of pressure and still 30 lbs at idle


SNAKE OIL INDEED
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  #15  
Old 11-18-2006, 06:35 AM
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i wouldnt hesitate to do as the previous poster said.

heavy oil and some lucas might do the trick for you if there isnt too much looseness.

it couldnt hurt.

tom w

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..I also have a 427 Cobra replica with an aluminum chassis.
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