1987 Dodge Truck Low oil pressure when idling, but fine at

JLHDU

MEMBER
1987 DODGE TRUCK
V8
2WD
AUTOMATIC
106,500 MILES

Hi,

I have a 1987 Dodge Ram D-150 (106,500) that may be on the front end of trouble. I've only noticed it recently (since it is warmer now), but the oil pressure seems to drop when stopped at a light (I can watch it tick lower-line by line, and lower the longer I sit). If I rev the engine, the guage indicator goes up as if it may be getting the necessary pressure.

When at highway speed the guage reads perfectly fine in the middle. I recently changed the oil and didn't notice any metal shavings, or anything else abnormal. I'm using 10/30 oil and haven't noticed any noise when the pressure drops (but will keep an ear out for it).

I don't want to go and start changing parts without some sense of direction. Any ideas?

5 Replies

RACEFAN966

MECHANIC
5,029 POSTS

How old is the oil in the engine now (how many miles sense last oil change)? I would first change the oil sending unit sense there isn't an ohms test to do on it that I can find. Let me know what you find and we will go from there.

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Thursday, June 25th, 2009 AT 9:31 AM

JLHDU

MEMBER
3 POSTS

Thanks for the reply, I changed the oil about 2 weeks ago (25 miles maybe) and am over the line by about a 1/4 quart. It does burn some oil (however slight) from the engine area (not through the tailpipe).

I don't drive this truck much, it's primarily used to haul to the dump (5 mile round trip) for the last 10 years.

Sorry to ask but is changing the oil sending unit difficult? Or costly?

Thanks,

Jason

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Thursday, June 25th, 2009 AT 9:40 AM

RACEFAN966

MECHANIC
5,029 POSTS

No it isn't hard to change just unplug it unthread it thread in new one and plug it back in. It shouldn't be more then about 33 dollars. If it is still reading the same then the engine is getting tired and what I would do then is get a quart of lucas oil stabilizer and add this to the oil. But you will have to drain a quart of oil out first and I would do that by removing the oil filter and drain the filter put it back on start the truck till the pressure comes up and check it do this till you are a quart low then add in the lucas. Here is a pic of the oil sending unit so you can find it on your engine. It should be near the oil filter.

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Friday, June 26th, 2009 AT 9:08 AM

JLHDU

MEMBER
3 POSTS

Thanks for your assistance. Just a quick follow-up, I drove the truck yesterday about 30 miles (risky I know), 15 each way and like clockwork as soon as I stopped at a light, sometimes as I was slowing from 20 mph and below I could actually see the pressure guage going down (kinda like a temp guage). The only remedy I found that kept the guage just below half way was to put the truck in neutral and rev the engine as if I was at driving speed. Does this info provide for any other possibilities?

Thanks in advance!

Jason

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Friday, June 26th, 2009 AT 11:46 AM

RACEFAN966

MECHANIC
5,029 POSTS

Have you replaced the sending unit yet? If not there is no way to know if the sending unit is sending the right signal at his point. It could be wore bearing in the engine or oil pump too but sending unit first.