(94) Recently I was running around allot in town driving hard(fast) and noticed my temp get to 240. I've seen in posts this is about tip top normal range, but car felt sluggish no warning lights came on, pulled over anyway to cool down. Anyway, ever since that day my oil pressure at the start of running is good but after about 30 min and the oil heats up to about 190 my pressure drops to 1-4 psi at idle and my check gauge starts to flicker, it goes off when I accelerate or put in drive and rmp come up just a bit. while running 30- 70 mph pressure shows 20-40psi. I changed my oil pressure switch today thats not it same results after new one. So is it possible I burned my oil when it got hot or maybe oil pump is going out? Again only happens at idle, Thanks for any help

Meds 94

 

You didn't "burn" your oil at 240* That oil pressure is too low however. have it checked out.

 

Step 1 is to verify that the oil pressure you are seeing is accurate. Hook up a mechanical guage to confirm.
If low, you can hope for 2 things.
1) Collapsed filter internals.
2) Pick up tube fell off of oil pump.

Outside of those 2 possibilities (for an easy fix), the other fixes involve engine teardown.

 

There's only one other 'simple' fix and it's kind-of a band-aid for loose bearing clearances and that's to drop the pan and put a HV oil pump in there - the extra volume should help keep the pressures up due to the large bearing clearances... Might even couple that with some fresh bearings in the bottom end and it should get you by for quite a while so that you can save up for a full engine build...

The only reason I say "kind-of" is that one of the bearings might not be wearing evenly I'd bet and if there is something causing excessive wear on that one or the bearing is real bad and starting to spin then it's just going to go bad unless they're replaced and the clearances are restored... Check the pressure with a gauge as suggested ASAP and don't run it at all or at least don't drive it hard until then - it could be costly!

 

What Pete said. The important thing is NOT to drive it until you get a fix on the problem. Driving with actual pressures in the ranges you cite equates to a very expensive repair very soon.

 

Didnt really wanna hear this, but guess now I can always rebuild it the way I want new heads intake cam upgrade and any other goodies.

 

What oil are you running - Brand - Weight?

Jake

 

Mobile 1 synthetic 5w30

 

As you probably already know, as oil temperature rises its viscosity drops. So at higher temperatures you'll see less pressure showing up on your oil pressure gage.

A change to 10W30 Mobil 1 MAY stop the red light oil pressure light flickering during in gear at idle conditions. It's still within factory oil specs if that concerns you. The caveat is the anticipated ambient temp should remain at 0 degrrees F or above during the time before the next oil change.

You can continue to do other diagnostic tests, etc., if you choose to, but in the meantime you'll have full use of the car without being concerned about the oil pressure being too low when sitting at a stop light, etc. That's if the oil weight swap does what I hope it will.

With my son's 96 LT1, I went with Mobil 10W40 to deal with the same flickering light/lower pressure reading issue. I only mention this to show what I ended up doing, since the Owner's Manual shows 10W30 as alternative to 5W30.

Jake

 

In this case what "helped" your son's car was the 40 portion of the oil viscosity - the first number is the winter weight or cold weather viscosity and the second number is the hot viscosity - going from a 0W30 to a 5W30 to a 10W30 at the same temp will all have the same hot viscosity of a straight '30' weight oil. To help solve a HOT oil low pressure problem an oil which gets thicker with temperature needs to be used so the second number needs to be higher. 10W40, 15W40, or even 20W50 would all be valid choices in this case...

At this point I wouldn't worry about the GM recommendations as the clearances they have engineered into the engine are obviously expanded and the thicker oil or additional pumped volume of oil is required to deal with those expanded clearances to maintain the pressure required to keep the engine from destroying itself.

Honestly if you do find low pressures as we expect then as easy as the pan comes off and as cheap as a HV oil pump is ($30 M55HV pump, $8 steel shaft and re-use the rubber pan gasket) I would spend about an hour and a half, drop the pan, put the pump in, and run a 10W40 oil and see how it does when hot.

 

If you are going to drop the pan, go ahead and put bearings in it. Pretty easy, except the front main. May be best to leave that one until you have the motor out. Or not.

 

Yes, absolutely correct and it's something I already knew.

Try to understand my position, I'm reluctant to recommend something that flies in the face of GM's stated recommendation. Had he PM'd me I would have told him, in a Private Message, what to do, but I'm reluctant to post such a recommendation for all the world to see.

Playing with different oil weights isn't the only thing I do differently from the GM recommendations. Sometimes I just do what works.

Glad you brought this out in the open though.

Jake

 

I just call it like it is... I just didn't want him to mis-interpret the viscosity and how oil weights are graded and think the 10W30 would be thicker hot then say a 0W30...

I call it like I see it - if you understand oil weight, flow and how the system makes pressure and how it relates to volume then you can make some informed decisions (which is often mis-understood by a LOT of folks I talk to...) - I wouldn't recommend a different oil on a new engine whose engineers spent time designing an oil pump to put out a specific volume and pressure for the bearing and other clearances that are machined into the engine - hopefully they did their homework to take all that into account

 

Thank you everyone for input, I am planning on dropping the pan and putting anew pump and shaft, will prolly even change bearings and noted above with a 10w40 weight oil even. everyone has been helpfull thanks again.

 

Right-O! We think alike on that.

Jake

 

try changing the filter first

 

Change the filter. 'Cause it's cheap and easy! I had my oil pressure start acting funny last year, pressure was really fluctuating really bad. I figured for sure my oil pressure sender was going bad. Changed the oil and filter (end of season) and this spring it was FINE

 

Based on previous experiences, I would make the filter change my first order of business. Especially if it is a Fram filter.
Before diving in, you did verify the presures with a mechanical guage though, right?
It would really suck if you invested alot of time and money to fix something that may not be broken.