outkast6991

iTrader: (34)

I need some help trying to diagnose an oil pressure issue i'm having on an lq4. i hooked a mechanical test gauge up to the pressure sensor port. when the car is in neutral it has 25psi at hot idle and builds pressure with rpm as it should. so i decided to leave the gauge hooked up and take a short ride. when the car is under load the pressure doesn't build at all and actually drops slightly under throttle. when i push the clutch in it builds pressure quickly (70psi) but as soon as the clutch is released it drops like a rock (under 20psi at times). when i stopped the car and left it in neutral it returned to normal and built pressure with rpm again. anybody have any ideas

joecar

Possibilities:
- crank thrust bearing;
- cam walking and/or bearing(s).

outkast6991

iTrader: (34)

thanks for the reply. any ideas how to narrow it down without yanking the motor?

01ssreda4

iTrader: (96)

Thrust bearing is moving too much under application of the clutch disk. Before you break down the motor, check the crank endplay. Sorry buddy, I went through this exact same thing. Here's my thread with pics of the damaged thrust.

https://ls1tech.com/forums/racers-lo...ew-engine.html

Be looking for .004-.008 as acceptable. Mine was .040. Thats 5 to 10 times too much depending on if you are using the low or high figure. The only thing that was stopping it from going any further is that the crank was rubbing the block itself internally.

jerflash

how much is the pressure dropping under load and does it still go up with rpm after its loaded?

outkast6991

iTrader: (34)

30psi at 4500. pressure will not build with rpm under load

01ssreda4

iTrader: (96)

sorry buddy, engine is likely trashed.

outkast6991

iTrader: (34)

yup i'm thinking the same thing is there any way to measure the endplay with stripping the trans out? looks like the Camaro motor is going in the GTO i guess

01ssreda4

iTrader: (96)

Absolutely, just takes about 5 minutes. Get the front of the car on ramps. Pull the main and ac belt off the front of the engine. Get a dial indicator with a magnetic base. Put the base on your sway bar and the dial indicator needle on your crank pulley. With a 1 to 1 1/2 pry bar. Pry behind the crank pulley. Gently as it will go past what you are supposed to be reading. Now when mine was .040 and my crank was trash, you could literally push and pull the crank by hand and it would slide forward, thud, slide back, thud, slide forward, thud. You get the idea. When its .004, you need the indicator to measure it, its very precise. At .040, it rediculously loose.

matt d.

Just for fun check the oil level.

01ssreda4

iTrader: (96)

That tells you its not an oil level issue. Pressure is relative to whether the clutch is pushing forward on the crank or not.

matt d.

That is what made me think it could be a oil level issue because it almost sounds like the oil is see- sawing around the pickup so to speak. But I could be wrong but for the OP I would hate to see him go through alot of trouble if it were something simple.

outkast6991

iTrader: (34)

oil level is good. i'm gonna try and check end play in the am

matt d.

Sorry to hear that sounds like bigger problems, let us know how it goes. Best of luck.