LT4 LT4 Low oil pressure

[Peabs]

Have a 96 w/LT4 and it has low to no oil pressure at idle and only about 10-15 at 3k rpm's. Also, at start up the pressure takes about 2 to 3 seconds to build up. Oil level is OK, clean and with Mobil 1 5W-30. No valve chatter or other unusal noise, but when I 1st noticed the issue the engine started to overheat. Needless to say it is parked in the garage. Bad oil pump? blocked screen? Bad filter? Other?;help

 

[LT4man]

I would attach a mechanical oil pressure gauge to where the oil pressure sending unit is attached at the rear of the top of the intake manifold.

A mechanical gauge does not lie and will tell you exactly what type of pressure you are pushing.

SAVE THE

 

[dmd]

You might get off easy with a clogged filter screen, bad oil filter, or worn oil pump, but I doubt it. Sounds like worn out main and/or rod bearings to me. After checking and ruling out the low-hanging fruit, get some plastigage, pull the pan and check all bearing clearances. If you've never done it before, have someone knowledgeable help you or take it to a pro.

 

[gmjunkie]

I would attach a mechanical oil pressure gauge to where the oil pressure sending unit is attached at the rear of the top of the intake manifold.

A mechanical gauge does not lie and will tell you exactly what type of pressure you are pushing.

SAVE THE

I'd bet it's the sending unit,otherwise you would have excessive lifter noise!!

 

[TedC]

I'm with LT4man and Junk on this one. If the LT4 oil pressure switch and sending unit is anything like one used on the L98, then they are not very accurate. I tested several units, and found the replacement from NAPA (grey) the closest to factory specifications (resistance vs. PSI). The AC Delco part looked identical to one from Autozone, and both were not as accurate as the NAPA part which was made in USA.

 

[LT4man]

My LT4, which I ordered new, has over 100,000 miles. I still have the original oil pressure sending unit. Oil pressure has been and still to this day is:

60psi on cold start and in cold weather never goes below 60psi.

In extremely hot weather, after warming up, 40psi at idle. 60psi upon acceleration.

When cruising, cold or hot weather: 60psi.

A mechanical oil pressure gauge connected in place of your sending unit will tell the tale.

WHILE CHECKING YOUR OIL PRESSURE, PLEASE SAVE THE !

 

[TedC]

LT4man, I'm in agreement with you. The original sending units are much better. On the L98 they were made in the USA using a steel canister. Replacements are mostly plastic. They are easier to install and remove because they are slimmer. I attached three replacements to a pressure line and varied PSI from 0-60 and monitored resistance. The USA made NAPA best matched the GM specs. I could vary the PSI +/- 5 and see no change on the replacement ACDelco or Auto Zone part. Hope you never have to replace yours.

 

[Peabs]

Thanks to everyone for your input. It turns out the oil pressure sender was no good. On the overheating, it was a seperate issue (bad relay). Thanks again!