Just bought 89 3500, some ?s New to gmc

duke-blue · 10-22-2006, 10:48 PM

New to this Forum....

Just bought and will soon pick up a 1989 3500 with 454. Seems to be fine but oil pressure drops when warm and when at a light with truck in gear and held by brake. Returns to normal when in park or when driving. I searched the forum and saw oil pressure sending unit or oil pressure sensor as potential problems Any best guesses?

I thought about an additive like auto rx... what do you think?

Will be driven 700 miles and don't want to mess up anything when driving it home. Motor is a factory replacement with 34k on it.

Any other special quirks or things to look for in this model? Thanks

mrjohnwayne · 10-23-2006, 08:24 AM

What does the oil pressure drop to? What is the difference between sitting in park and sitting in gear? How high is it when you are driving down the road?

duke-blue · 10-24-2006, 05:45 AM

It drops to about 7. I have not driven it, just going on the present owner's statements. Thay say "normal" when driving and when in park and have driven extrended distances with it like that, and daily with putting the car in park at stop lights.

chevyguy · 10-30-2006, 07:10 PM

Sounds like a bearing clearance problem. Had a customers 351 do the same thing recently. He changed the cam and damaged the cam bearing during the install. Low oil pressure is bad. Wouldnt think of driving 700 miles with low oil pressure.

project88 · 10-30-2006, 10:41 PM

wouldnt long periods of idle time in the vehicles life cause problems in the mains? i know of a few vehicles coming from up north with low oil pressure and mechanics say that it is because they sit idling for long periods of time and the mains need replacing. any value to this CG?

bradrhale · 10-31-2006, 10:23 AM

i dont believe you can let that engine idle long enough for cam bearings to go bad for that. if you had low oil pressure to start with, i might could see that just beacuse with every turn of that engine with low oil pressure is another nail in the coffin.

10-22-2006, 10:48 PM	#1
duke-blue Junior Member Join Date: Oct 2006 Location: NC Posts: 2	Just bought 89 3500, some ?s New to gmc New to this Forum.... Just bought and will soon pick up a 1989 3500 with 454. Seems to be fine but oil pressure drops when warm and when at a light with truck in gear and held by brake. Returns to normal when in park or when driving. I searched the forum and saw oil pressure sending unit or oil pressure sensor as potential problems Any best guesses? I thought about an additive like auto rx... what do you think? Will be driven 700 miles and don't want to mess up anything when driving it home. Motor is a factory replacement with 34k on it. Any other special quirks or things to look for in this model? Thanks

10-23-2006, 08:24 AM	#2
mrjohnwayne Moderator Join Date: Apr 2005 Location: Texas Posts: 3,104	What does the oil pressure drop to? What is the difference between sitting in park and sitting in gear? How high is it when you are driving down the road? __________________ John Wayne 2000 F-350 7.3L Powerstroke 4x4

10-24-2006, 05:45 AM	#3
duke-blue Junior Member Join Date: Oct 2006 Location: NC Posts: 2	oil pressure drop It drops to about 7. I have not driven it, just going on the present owner's statements. Thay say "normal" when driving and when in park and have driven extrended distances with it like that, and daily with putting the car in park at stop lights.

10-30-2006, 07:10 PM	#4
chevyguy Senior Member Join Date: Sep 2005 Location: ALABAMA Posts: 3,160	Sounds like a bearing clearance problem. Had a customers 351 do the same thing recently. He changed the cam and damaged the cam bearing during the install. Low oil pressure is bad. Wouldnt think of driving 700 miles with low oil pressure. __________________ When i die, i dont want to walk gracefully thu the pearly gates and turn in a unused body. i want to go sliding thru sideways and turn in a body that has been completely used up.

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10-30-2006, 10:41 PM	#5
project88 Senior Member Join Date: Feb 2006 Posts: 135	wouldnt long periods of idle time in the vehicles life cause problems in the mains? i know of a few vehicles coming from up north with low oil pressure and mechanics say that it is because they sit idling for long periods of time and the mains need replacing. any value to this CG?

10-31-2006, 10:23 AM	#6
bradrhale Moderator Join Date: Apr 2006 Location: Texas Posts: 2,772	i dont believe you can let that engine idle long enough for cam bearings to go bad for that. if you had low oil pressure to start with, i might could see that just beacuse with every turn of that engine with low oil pressure is another nail in the coffin.

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