I have an 87 gta trans am that has low oil pressure at idle after it warms up. The oil pump is new, does anyone know what causes this? I have been told that if the cam or crank bearings are worn it could cause low oil psi. any advice would be welcome. Thanks---Tom

 

I have an 87 t/a with a 305 tpi engine. I have low oil pressure at idle after it warms up, the oil pump is new. Any help would be appreciated. Thanks---tom

 

Just a few questions to possibly help get to the answer:

1. What oil are you using (Viscosity and type, please)?
2. What is the ambient temperature?
3. What is the coolant temperature when the pressure drops?
4. What gauge are you using to read the oil pressure?

Those answers might help.

 

10w-30 oil, temperature is about 195 after warmup, using a mechanical pressure gauge

 

And what is the pressure reading under those conditions? "Low" can be a very subjective term. 10 PSIG would not necessarily be "low".

I also forgot to ask, what idle RPM?

 

approx. 10 psi or less at 650 to 700 rpm's. I had to put valve guide seals in it, the old ones had disintergrated and fell into the pan that's what caused me to replace the oil pump while i had it apart. Do you think a piece of the seal could have gotten into the channel that leads up to the gauge?

 

If you suspect that, you may be able to connect a gauge at the front of the engine, above the timing cover.

10 PSIG at 1,000 RPM is generally enough, provided the pressure increases with RPM.

 

is there a plug or something that also has oil pressure to it at that location? I've never come across a motor that has this low psi before. The pressure does increase with rpms but it just seem wierd for it to be so low and I'd hate to keep driving it and possibly blow it up. Do you have any other suggestions? Maybe going to a different spring in the pump or something? Thanks for all your help. ---Tom

 

What pump/spring did you install?

If you installed a high volume pump (typically longer geares) the pump pickup may be too close to the bottom of the stock pan. Make sure you have about 3/8-1/2" of clearance between the pickup and bottom of the sump. (Don't ask...)

For most any application, the stock pump provides adequate volume to maintain good pressure. If the rear main bearing was installed incorrectly, the plug in the passage from the rear main is missing, a bearing(s) is improperly installed, the lower distributor housing is damaged, one of the lifter gallery plugs has blown or rotted out, or there are excessive clearances, oil pressure will be lower.

A weak relief spring can do the same.

There are some aftermarket and production crankshafts that have balancing holes in the counterweights which are drilled too close to oil galleries in the crank, and can leak enough to cause low pressure/no pressure.

There are other possibilities, but those are common ones.

 

i had low oil pressure, it was up about 1/4 of the gauge at cold, then 0 at warm, i switched to a mechical fuel gauge and everything is fine now it is normal cold and warm. the oil sending unit was bad

 

I'm not intentionally ignoring that question. I've been searching for a photo of a later block that clearly shows the front plug. Most later SBCs have a 1/8" NPT plug on the right side just above the timing cover. This is another place to test pressure.

 

Give me a second if i can find my camera ill get a pic for you. My 350 sitting right beside me has the plug on the front by the timing chain.

 

Ok that was more than a second but who would have thought 4 AA batteries were that hard to come across??

 

cool thanks for all the info. I'll check the pressure at the front hole in the a.m. and let you guy's know what I come up with. I did install the high volume pump and I'm not sure about the clearance issue but, when I installed it I purchased a new sump with it and installed it at the same angle as the old one.

 

Yeah, those mechanical gauges are alot better than those mechical ones!

 

If you noticed he said fuel gauge too

 

DAMN! That one slipped right past me! That's what wild turkey does to people!!!

 

well esqueeze me!!!

 

So? Get a reading at the front yet?

There may be debris in the oil passages, but that might not necessarily cause a low reading. You could pull the line from the gauge, crank the engine to purge the passage, and reconnect to be sure. It might be messy, though.

 

Well something burned out in the wiring and now she won't crank , so I've got to look at that in the a.m. but I was thinking about your comment on the distributor coupling with the oil pump shaft. I'm going to pull the distributor and check the bottom of it, because if thats stripped it would cause my exact problem. I'll let you know how I make out. Thanks---Tom