Oil Cooler Bypass Valve- Cause of low oil pressure when car is warm?

[Eric_VR-4]

It sounds like a part that should be replaced every 100K or so.. why not just get a new one from Mitsu?

Oh.. I checked my hot idle pressure today... on the stock gauge it reads 3.5 clicks up.. counting the larger bottom one as Zero. I remember taking the tiny dent out of the oil pan helped too. The stock gauges are so worthless it is impossible to tell if my pressure is better than anyone elses... just what has helped that I have done... front mount.. and bang out the dent.

[BlackStealth]

I can still put my original one back together, as I didn't damage anything in the process. But I'm gonna cough up the money, and buy a fresh new one from mitsubishi instead. Here's the part number in case someone is looking to buy new:

MD041092
MD356695 (newer part number).

I'm still crossing my fingers hoping the new one will help.

[Supercar]

Originally Posted by lethal_vr4

Call Philip @ SCE.. I know he has a *spare* perhaps he will sell it to you.

Hmm... I thought I did not have it, but I guess I do now. A spare bypass valve arrived today with a new oil filter adapter that I had broken. Brand new. PayPal me $20 and you will have it by the weekend. Thanks.

$20 shipped

Philip

[BlackStealth]

Well, I took out my old oil cooler bypass valve out today. My missing part was still attached to it!! After shining the light down in the hole it doesn't look like it would have caused any damage anyways. Too small of a passage for the missing part to pass through. So I've never really experienced this mod first hand since I just replaced it with a brand new factory piece.

I did notice that the new factory piece is designed slightly different. The spring is now wider, and a few other minor changes. This probably explains why the mitsubishi part number has been replaced with another.

I couldn't back my car out of the garage, so I had my car idle for about 10 minutes. To my disapointment, I was two ticks below normal (the first large tick from the bottom). Although my car has gone as low as 3 or 4 ticks below the large tick after extended idling from real driving. I'll report my findings again to see if there was any improvements. But first impressions isn't good.

[BlackStealth]

Update: Replacing the oil cooler bypass valve with a new one made no difference. So don't waste your money on a new one. The problem lies somewhere else. Maybe a clogged oil cooler?

[drone007]

i have no valve in the oil housing, but my front mount oil cooler is hot to the touch. i think i'm getting oil in it....

[306GTO]

I'm not buying the anti literature here. My car had a problem with low oil pressure. With new oil, it had normal pressure for about 500 miles, then would run low, at idle and at speed. I changed the oil every 1000 miles because it was getting very burnt and blackened in that amount of time. Every time I changed the oil, pressure was normal for 500 miles, then low after that. I took the engine out and gave it a fresh rebuild. Including a brand new oil pump!!! I can guarantee there is NOTHING wrong with the motor that would cause low oil pressure. When I got it in and running again, it ran at the EXACT SAME OIL PRESSURE!!!!!! Normal for about 500 miles, then low after that. Less if I raced a lot. I was pretty pissed off. To make a long story a little shorter, I gutted the valve and now have good oil pressure at idle AND at speed. Oil change at 1500 miles after gutting the valve, guess what? NO BLACK OIL!!! There's NO WAY gutting that valve is completely bypassing the cooler. And there was no pressure drop during those 1500 miles like there had been before after only 500.
Needless to say, I'm going to purchase a new valve and put in. Just like removing your thermostat: coolant doesn't overheat anymore, but it's not regulated. So I'm not going to run without the valve much longer, I'd prefer to have the temp regulated. But I will choose to run unregulated than to run overheated.
I would recommend to everyone to put in a new valve that has oil pressure problems. Even if you don't. Why would you keep a 14 year old thermostat in your car? Even if it did work just fine. You're not going to bust the bank buying this thing.

[2Mitsus]

Originally Posted by 306GTO

I'm not buying the anti literature here. My car had a problem with low oil pressure. With new oil, it had normal pressure for about 500 miles, then would run low, at idle and at speed. I changed the oil every 1000 miles because it was getting very burnt and blackened in that amount of time. Every time I changed the oil, pressure was normal for 500 miles, then low after that. I took the engine out and gave it a fresh rebuild. Including a brand new oil pump!!! I can guarantee there is NOTHING wrong with the motor that would cause low oil pressure. When I got it in and running again, it ran at the EXACT SAME OIL PRESSURE!!!!!! Normal for about 500 miles, then low after that. Less if I raced a lot. I was pretty pissed off. To make a long story a little shorter, I gutted the valve and now have good oil pressure at idle AND at speed. Oil change at 1500 miles after gutting the valve, guess what? NO BLACK OIL!!! There's NO WAY gutting that valve is completely bypassing the cooler. And there was no pressure drop during those 1500 miles like there had been before after only 500.
Needless to say, I'm going to purchase a new valve and put in. Just like removing your thermostat: coolant doesn't overheat anymore, but it's not regulated. So I'm not going to run without the valve much longer, I'd prefer to have the temp regulated. But I will choose to run unregulated than to run overheated.
I would recommend to everyone to put in a new valve that has oil pressure problems. Even if you don't. Why would you keep a 14 year old thermostat in your car? Even if it did work just fine. You're not going to bust the bank buying this thing.

I agree- except as antero noted, he replaced the valve with no difference. Apparently the valve must be gutted to gain any benefits from doing this, although I can't say firsthand since my valve is still gutted and I never bought the new one.

Anyway, a couple of opinions on your post and this mod:
Why gutting it works, I don't know.
Whether the oil is hotter or cooler by gutting it, I don't know.
Is the valve or oiling system flawed by design, or is it a part failure? I don't know.
Is more or less oil going through the cooler? I don't know.

What I do know is this-
Gutting the valve increased my pressure, as indicated by an aftermarket gauge.
Gutting the valve, has increased the pressure of everyone who has done it and posted results in this thread.
My oil cooler is hot to the touch after driving, as is drone007's so I believe oil is going through the cooler (athough to what degree).
I personally would have a major gain in oil pressure, and not have my warning light flicker by doing this simple mod, then worrying about it every time the car is idling when hot.

I encourage everyone to make their own decisions regarding this, weigh the pros vs possible cons, and come to your own conclusions. I for one, am going to leave my valve gutted, and enjoy my higher oil pressure, until proven otherwise (or until my car blows up).

[Supercar]

I still have a brand new valve that was left after I bouhgt a new oil filter adapter. What's a dealer price on it? Make me some offer before I lose it or throw it away. The first offer that is worth a 5-minute trip to the post office gets it. Thanks.

Philip

[Bret Brinkmann]

Originally Posted by 2Mitsus

...Gutting the valve increased my pressure, as indicated by an aftermarket gauge....

This experiment can ONLY be conclusive if using an AFTERMARKET oil pressure gauge. antero's findings are with the OEM gauge which is proven to be highly inaccurate. (Not trying to start anything here antero I'm just saying the OEM oil gauge is not reliable.) The OEM BOOST gauge is more accurate than the oil gauge. Plus, the sending unit for the OEM oil gauge has been known to have it's resistance change over time as evident by those who have reported "increased oil pressure" simply by swapping out a brand new sending unit.

So far, every one with an aftermarket gauge has reported increased oil pressure. I have an Auto-Meter electronic full sweep oil pressure gauge. I currently have about 11 psi @ 800 RPM @ hot idle. Next pay check (this Firday) I'll be buying an Auto-Meter electronic full sweep oil temp gauge. (I was gonna buy one any way just not so soon.) I'll report my temps vs press findings and then swap out oil by-pass valves and report my findings sense no one else seems interested in getting to the bottom of this. (This is a great excuse to buy some gauges guys come on! )

I would also like to bring up Pascal's Law. "Pressure with in a sealed hydraulic system is equal in ALL DIRECTIONS." Knowing this how can the oil either going through or by-passing the cooler change pressure (assuming equal temps) sense it is located AFTER the oil pressure regulating valve? That would be like saying what oil filter you run changes oil pressure. I have tested the filter theory with my aftermarket gauge and found that what filter you run makes no difference.

Speaking of oil coolers. Your cooler and cooler lines should be free of leaks. I have heard of several members with leaking oil cooler line seals that dripped oil on the cooler and gummed it up. This prevented air flow through the cooler and reduced their hot oil pressure. After they cleaned the exterior of the cooler they reported a few psi increase in oil pressure. You should also fill the cooler up with oil after cleaning and drying so your engine doesn't get a big shot of air when oil first goes through it.