Fixed my rod knock..but still low oil pressure...oil cooler question I guess?

[lewis87mk3]

Alright, I've owned a few supras by now, they are a learning experience.. I get better and better but I still make my mistakes.

Last mistake was, I did an oil change with 5w30 or 10w30 oil, and after 15mins of driving my oil pressure acted weird ups and downs. I replaced the gauge, and replaced the sensor... then it seemed like it was functioning right, but the oil pressure would stay at zero for most of the time, if I reved it, it would go up, then holding the rev, it would steadily drop back down to zero.
Like a dumbass, I assumed it still to be a bad gauge or sensor, and kept driving.

Got a rodknock, stopped driving soon after... dropped the front end, checked out the oil pump, took it apart, checked clearances, it was fine.. replaced the one rod bearing that wasnt that bad but just enough for a knock. Threw everything back together... easier than expected.. put 20w50 in it this time, castrol gtx......
Now things are looking kinda better.. cold idle is 40psi pressure, up to 60 or 70psi reving some..
But after warming up, around 2k rpm its about 20psi, idle closer to 5-10psi.. and reving it never really goes much past 40psi.

I really think I should have more oil pressure, my question is... aside from taking my car all apart again like I will have to....are there things I could check like perhaps the oil cooler? Could the oil cooler cause me to have this lower oil pressure? I doubt its ever been flushed or anything, the car is 20 years old now...
I'm going to flush it anyway, and probably replace the lines, but does this sound like a symptom of the oil cooler?
How exactly is the oil cooling system supposed to work on a 7mgte?

Also, is it possible that the timing belt might be loose when the car warms up and slipping on the oil pump pulley? or is that a toothed gear... I hear no belts slipping when driving.

 

[starscream5000]

The oil pressure you are describing is pretty typical in our engines. put that 5-10w30 back in there.....:3d_frown: There's plenty of threads on here covering oil and our engines.

 

[mhopemk3]

I have a relocation kit and my idle oil is around 5. When I am driving it never goes above 22-24..

 

[starscream5000]

^ You post whore, you could have edited you first instead of doing a new one .

 

[lewis87mk3]

I know it should have more pressure though...
Perhaps thats why everyone ends up with rodknock.

with 5/10w30 in there, I had even worse horrible oil pressure in there, which I believe to be the cause of my rodknock in the first place.

Does anyone know anything about the oil cooler?
I think I read something somewhere about a spring valve that opens/closes the cooler lines based on pressure. I'm thinking that theres a possibility for mine to be sticking open, but would it do that? and would it have those symptoms as far as oil pressure goes?

 

[starscream5000]

If you've got rodknock, a heavier wieght oil isn't going to fix the problem. All you are doing is killing the bearings faster on startup with the heavier oil and making the oil pump work even harder trying the push the thicker oil through the engine. That's why you show more oil pressure with the heavier one .

 

[williamb82]

http://www.supramania.com/forums/showthread.php?t=31378

 

[lewis87mk3]

http://www.supramania.com/forums/showthread.php?t=31378

I saw that post, very nice... Unfortunately more than I can get into for right now.

 

[hottscennessey]

You're correct.. the oil cooler is on a valve that opens at a particular oil pressure. If the spring is worn, then the valve could pre-maturely open and cause a 10% oil PSI loss (says IJ ) This is because that pressure goes through the oil and goes back into the oil pan; basically wasted pressure.

However, it doesn't sound like this is the case because your oil Psi is better than mine . If I were you then I'd stick to shimming the oil pump, and an oil filter relocation kit. Based on the information we have on different oil weights, I'd throw back in the lower weight oil.

 

[lewis87mk3]

You're correct.. the oil cooler is on a valve that opens at a particular oil pressure. If the spring is worn, then the valve could pre-maturely open and cause a 10% oil PSI loss (says IJ ) This is because that pressure goes through the oil and goes back into the oil pan; basically wasted pressure.

However, it doesn't sound like this is the case because your oil Psi is better than mine . If I were you then I'd stick to shimming the oil pump, and an oil filter relocation kit. Based on the information we have on different oil weights, I'd throw back in the lower weight oil.

Thank you, thats the info I needed.

 

[lewis87mk3]

I read this about oil weights, http://supraforums.com/forum/showthread.php?p=3234214&page=1&pp=25

I was going to go with 10w40, but I stepped it up to 20w50...
I don't know really..I couldn't make sense of a lot of the article, so if someone has better advice let me know.

But with my hard driving style...and my old tired engine...my oil gets hot, and its my understanding that when 5w30 oil gets hot it thins out even more and more to where its hardly even acting like oil.

I don't really find myself driving the car too lightly when I do.. I have a daily driver for that.

My thoughts are that if I start it up, wait till oil pressure builds up before reving it.. and drive it lightly until it warms up, a heavier weight oil would be better for me.

Do you guys honestly think I should change oil again?
I mean I have to change my oil again anyway, usually after doing major work I like to change it at least 1 week from the first change.

If I do, ill probably go 10w40.. but 5/30 is something I don't know if I have the balls for again, it scared me because my oil pressure would sit at zero most of the time even when reving after a hard driving session.. then I got a rod knock.

Shimming the oil pump pickup is not something I really want to do either, I had another engine die on me because I somehow punched in my oil pan a little and it was bad enough to push the screen mesh of the pickup right up against the feeder hole, which in turn starved the pump of oil over time, whether it clogged up or who knows what, I dont know. But dropping the pickup lower would just mean that if I damaged my oil pan again, its more likely for that to happen again.. The oil pan on our cars sits pretty low and its fairly easy to bang up... I've seen it happen several times. I'll just check my oil frequently and should be no problem.

 

[jdub]

The 5/10W-30 oil did not cause the rod knock...excessive rod bearing clearance did.

Bearing wear is caused from the bearings just wearing out with high mileage or inadequate oil flow. Oil pressure does not = oil flow. Pressure is produced when the oil flow from the pump meets resistance, in the channels through the motor and the main/rod bearings. The tighter the bearing clearances (like in motor w/ a re-worked crankshaft & new bearings), the more resistance there will be to the oil flow and produce higher oil pressure. The oil pump itself can cause low oil pressure from inadequate flow...you have to have the flow to produce the pressure. Keep in mind that bearing clearance increases of as little as 0.001" in some motors can cause a 20% decrease in oil pressure....bearing clearances is the #1 reason oil pressure is produced in an engine.

In a tight clearance motor (like the 7M) that is why you want to run a 0W or 5W-30 oil...it flows into the bearing clearance better cold and keeps the oil film thickness required to provide the lubrication needed to minimize bearing wear. A 20W-50 oil does not flow into the bearing clearance very well at all...especially cold and is not better at maintaining oil film thickness. On a high mileage motor, the highest weight oil I would ever use is a 10W-40.

Your oil pressure is not bad for a stock 7M...idle is usually 3-5 psi...at 3000 rpm it is approx 30 psi. The 7M is a high volume, low pressure oil system. If you want a little more pressure, you can shim the oil pressure relief spring on the pump as mentioned above...I wouldn't go more than 2 washers (~2mm thick). That will give you about 10 psi at idle and 40 psi at 3000 rpm using a 0/5W-30 oil.

 

[againstdawall06]

Most people get rod knock due to not having enough oil in the engine, me being one of those people. Im sure you have heard that 99% of the time it is the owner, which is mostly true. I would use a synethetic 10w30, the aditives stick to surfaces to lubricate better even when the oil is hot. Also, the oil pressure that you have is within spec. And you can never check your oil to much.

 

[againstdawall06]

The 5/10W-30 oil did not cause the rod knock...excessive rod bearing clearance did.

Bearing wear is caused from the bearings just wearing out with high mileage or inadequate oil flow. Oil pressure does not = oil flow. Pressure is produced when the oil flow from the pump meets resistance, in the channels through the motor and the main/rod bearings. The tighter the bearing clearances (like in motor w/ a re-worked crankshaft & new bearings), the more resistance there will be to the oil flow and produce higher oil pressure. The oil pump itself can cause low oil pressure from inadequate flow...you have to have the flow to produce the pressure. Keep in mind that bearing clearance increases of as little as 0.001" in some motors can cause a 20% decrease in oil pressure....bearing clearances is the #1 reason oil pressure is produced in an engine.

In a tight clearance motor (like the 7M) that is why you want to run a 0W or 5W-30 oil...it flows into the bearing clearance better cold and keeps the oil film thickness required to provide the lubrication needed to minimize bearing wear. A 20W-50 oil does not flow into the bearing clearance very well at all...especially cold and is not better at maintaining oil film thickness. On a high mileage motor, the highest weight oil I would ever use is a 10W-40.

Your oil pressure is not bad for a stock 7M...idle is usually 3-5 psi...at 3000 rpm it is approx 30 psi. The 7M is a high volume, low pressure oil system. If you want a little more pressure, you can shim the oil pressure relief spring on the pump as mentioned above...I wouldn't go more than 2 washers (~2mm thick). That will give you about 10 psi at idle and 40 psi at 3000 rpm using a 0/5W-30 oil.

On a "tired old engine" wouldnt it be better to run something more like 10w30?

 

[jdub]

On a "tired old engine" wouldnt it be better to run something more like 10w30?

I said the "highest weight"...

Remember, the bearing clearances are making the pressure (or at least most of it)...if a 10W-30 gave me normal oil pressure readings, that's what I would use.

 

[dbsupra90]

the service manual says-
4.3psi at warm idle
36-71psi at 3k rpm warm

also i change my oil and filter every 5k miles and use 10w40 as the manual suggests.

 

[jdub]

That is the oil pressure test...measured using a calibrated oil pressure gauge installed at the sending unit location on the block. The gauge on the dash is not that accurate

 

[87nasupra]

I think alot of the 7m's that havent had any major engine work done mostly produce around 3-5 psi @ idle and drive between 20-25 psi. Our oil pump is a Low pressure-high volume pump. Your fine if you run a 10w-30 synthetic oil. I do an im only N/A :naughty: