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General Forums => The Mess Hall => Topic started by: jcguin on June 28, 2006, 07:57:28 AM

Title: Oil Pressure Drop at idle
Post by: jcguin on June 28, 2006, 07:57:28 AM

Lately when I come to a stop, my pressure will drop almost to to zero.  The check gauge light will come on.  I can run up the rpm's and it will be ok.  Typically I run around 40 psi at speed.  This does not happen always, just occasionally.  Any ideas?

Title: Oil Pressure Drop at idle
Post by: yellowta on June 28, 2006, 11:35:04 AM

Check the sending unit and oil filter. My old YJ used to do that, the passages to the filter and sending unit were all plugged up with goo :lol:

Title: Oil Pressure Drop at idle
Post by: Jeffy on June 28, 2006, 12:45:49 PM

I'd probably suspect the oil pressure sender.  They're pretty cheap and easy to replace.  Takes 1-2 minutes.

Title: Oil Pressure Drop at idle
Post by: Oilsmoke on June 28, 2006, 10:01:57 PM

How many miles on the Motor?
Worn main bearing can drop low rpm oil pressure.
If the other stated problem check out try
heavy weight oil,  don't bleed out as fast.

Title: Oil Pressure Drop at idle
Post by: jcguin on June 29, 2006, 09:26:24 AM

It has 173K miles on it, but when I bought it he said the engine was rebuilt.  So who knows.  I'll swap out the sending unit first.

Title: Oil Pressure Drop at idle
Post by: jcguin on June 30, 2006, 06:51:51 AM

One more indication to add.  It only happens when the engine is really warmed up.  When it is cold, it will hold around 30-40 at idle.  

Thanks guys

Title: Oil Pressure Drop at idle
Post by: Jeffy on June 30, 2006, 12:11:17 PM

When was the last time you did an oil change?

Title: Oil Pressure Drop at idle
Post by: Oilsmoke on June 30, 2006, 03:13:16 PM

It really sounds like worn main bearing to me.
what weight oil are you running in it?.

Title: Oil Pressure Drop at idle
Post by: jcguin on July 05, 2006, 07:05:24 AM

Sorry for the delayed response,,, I've been off.

I had the oil changed two weeks ago, it was castrol 30 weight.

Yall think I should change it again to 50?

Title: Oil Pressure Drop at idle
Post by: Oilsmoke on July 05, 2006, 08:37:03 AM

I would try 20/50. weight But remember this is not a fix but a band aid to the problem. If this helps it's worn mains.

Did you try a new pressure sensor? Were the passages clean, When the oil change was done what condition was the old filter in?

Title: Oil Pressure Drop at idle
Post by: Sidscan on July 05, 2006, 12:29:24 PM

I had the exact same problem with my 97 tj.  The heat started to pickup in the Seattle area and the check guages light started to beep once and awhile when my wife drove.  I took it on a freeway drive with her and when we got off and stopped at the traffic light the check guages light clicked on and stayed on until I reved it.  I got real scared thinking I lost oil pressure or worst the oil pump.  The strange thing was that when I started driving the pressure would pop back up to 40 - engine ran fine.  

I tried to recondition the switch like DYI board posted without luck.
I went to Pep Boys and got a Borg Warner replacement Oil pressure send/switch ($24.95) because after reading several boards it became clear that the switch malfunctions rather frequently.  Real easy to replace, just go easy with a adjustable wrench.  10 minutes tops.  

Didn't fix any idle problems because it is just a indicator switch.  Still trying to figure out why my idle jumps up especially when warm.  Waiting shouldn't hurt you unless you rely do have a problem.