I have a 1995 montero SR 6G74 DOHC Engine and for about one moth I have notice that my oil pressure gauge does not mark any oil pressure (0 PSI), when the engine is hot and between idle speed and 2000 rpm; just when I speed it up to 3000 rpm it begins to mark and goes up to 60psi.
Otherwise when the engine is cold and at idle speed it marks 40psi. Is this Normal?
When the engine is cold and I start it up I have to keep my foot on the gas pedal for about five minutes and wait the engine to heat up, if not it goes off. What could be wrong?

Does the oil pressure warning light work? The Montero doesn't have a 'real' oil pressure gauge. I was getting low (<10psi) readings on mine. I replaced the sender unit with a generic unit and it reads within the normal range now. It's really, really easy job to do when changing the oil. If you really did have 0psi oil pressure at idle your HLAs (lifters) would be clattering like crazy. I plan on getting a real gauge in the future. Anyhow, if your pressure is still a little low try a Mitsu filter if you don't use them already. If it's STILL low, you've probably got a weak pump.

Good luck. <img src="/forums/images/graemlins/kewl.gif" alt="" />

I have found the stock gauges were not too reliable, atleast on my gen1s. I have changed out the sending unit and gauges. I left the same sending unit and switched the gauges out and got a different reading. But the ones I was using were around 13-15 years old though. Mine do read consistant, I just dont think they are exact. I know a couple people used aftermarket gauges. Someone will chime in and give you more info.

I agree. My Gen2 gauge flopped to 0psi while I was driving up the highway <img src="/forums/images/graemlins/scared.gif" alt="" /> and then I realised the warning didn't work either <img src="/forums/images/graemlins/rolleyes.gif" alt="" /> However, the engine was quite (no clatter) and wasn't getting hot, so all was fine <img src="/forums/images/graemlins/kewl.gif" alt="" />

A mechanical pressure gauge would be nice.

I installed an Autometer electric oil pressure gauge right above the locker switch on my SR. I also retained the idiot light, but replaced the switch with one that goes off at like 12psi vs. <10psi.

I will change the sending unit maybe it?s damaged.
But what about the idle speed problem when the engine is cold, what can I do to fix the problem?

I had a similar problem on the Jeep GC (<img src="/forums/images/graemlins/ignore.gif" alt="" />) I used to have. Turned out to be a fuel delivery problem. A new fuel filter and a tank of gas with good injector cleaner fixed it. This may not fix your problem, but it's cheap and easy to try it.

Reuben, where is the sender unit located so i can check it out myself too. Good advice guys <img src="/forums/images/graemlins/kewl.gif" alt="" />

Angelo

It sits just above the oil filter with a single wire attached. Looks like this. I've forgotten what size wrench (spanner in English <img src="/forums/images/graemlins/ignore.gif" alt="" />). Anyhow, I got mine from Advance for $35. They had to order it <img src="/forums/images/graemlins/rolleyes.gif" alt="" />, but the sender was $60-65 at the stealer. I got a tube of thread sealer too, but I lost that and changed it without (where's that shady tree)!! I'll check tonight to see if it's leaking <img src="/forums/images/graemlins/rolleyes.gif" alt="" /> My oil pressure (with Mistu filter) now runs between 30 and 60 psi (idle - highway) hot. Of course it's still a crappy gauge and I wonder if you could get 'real' gauge for similar money.

Out of interest I used 10W40 high mileage oil. My lifters weren't so happy with that as they were with 10W30. They aren't noisey but I can hear them.

Ooops, I was wrong about the pressures. I went back and did some digging.

For the gauge, I purchased it from Summit. It's part # ATM-2634 . I had to get a metric adapter ATM-2269 and a 1/8npt t-fitting. I also bought an low oil pressure kill switch from Summit part# SUM-G1438 . I'm using this switch to activate the idiot light ONLY. It operates at 7psi vs the factory 5psi AND it has a 1/8npt fitting on it, which made it easy to thread into the above t-fitting.