Oil Relief Valve No Good, What should I do? I need advice

[mitch32]

I posted this on gtrcanada.com (link) but I was hoping some guys here may have advice.

My car is a 1991 r32 GTR with 109,000km. Compression is 165psi across the board, cyl-6 is 170psi. Upgrades are exhaust, and intake.

So my problem is that I have good idle oil pressure and good oil pressure up until 3000rpm. After 3000rpm the pressure never increases. Its as if the gauge just gets stuck. I checked with mechanical gauges, changed my stock sending unit, used a defi gauge, everything gave the same result. I have maximum 2.8bar no more. I read alot and I'm pretty sure its the relief valve, but also I read it could be bearings. If its bearings though wouldn't my idle pressure be wrong? Also I never get more then 2.8bar on a cold start.

I'm not sure what to do. I'm kinda of just leaning towards changing the oil pump to an N1, its a big job but I can do it at a buddies garage on a lift (hopefully within a weekend, or a day) and hoping my oil pressure is good after the swap. Then waiting until it blows completely and do a rebuild then. I'll probably also do the timing belt (and water pump) with the oil pump eventhough my timing belt is fairly new. I want to avoid a rebuild right now if I can, I barely driven the car since I bought it, also I have alot of parts waiting to be put in. I just don't want to put the parts in until I get rid of this issue.

Tell me what you think! Can it be the bearings also, what would you do?

Thanks in advance,
Mitch

[mcfly]

You make it sound like changing the oil pump is an easy task. Unless you plan on cutting and drilling your oil pan you will need to pull the engine. Both ways take essentially the same time.

Do you have enough oil in the car?
you have changed your oil filter?
do you have any oil leaks?


There is a big possibility that the oil pump is worn out rather then the bearings being worn enough to cause this issue. There is an oil pressure regulator in the oil pump which may also be faulty.


I highly doubt that the oil relief valve is causing your issue but you could always take the oil filter pedestal off and inspect it.

[mitch32]

It seems I have no leaks. I changed the oil twice in 1000km with Motul 15w50. I also tried two different filters.

I actually had thought the oil pressure relief is in the pump itself? I didn't know there was another one behind the filter.

I also know its a massive job to do the oil pump, and once I'm there I should do everything, crank, rod bolts, bearings, baffle plate, timing belt, water pump, etc... but I didnt want to invest that kind of money into an old engine. If I was rebuilding it then I'd be more willing to put in the necessary funds. I also want to avoid a rebuild. Right now I kind of just want to make it work and then in a year or two do a rebuild. So should I do a rebuild? Should I just replace the oil pump? Should I replace the oil pump and the associated parts? Should I swap in a working engine?

All are big tasks. I don't know what the best solution is. I also bought the car and didn't even think to check an issue like this and now I'm in a position where a proper descision is necessary.

[mitch32]

I actually just read of someone with the same issue as me. He informed me that the screws on the back of the oil pump that hold on the plate have a tendency of coming loose. It isn't the oil relief according to him and he said other people had the same issue causing the same problem. Looks like my engine is coming out, which I was gonna do anyways. I think I will only do the oil pump, timing belt, water pump, crank collar and crank balance, and an ATI damper, lastly if I can get a hold of oil pan baffle I will put that in. I will inspect the journal bearing and if they are good I won't replace them. So other then that I don't know. I was considering buying a new crank but if I'm going that far I guess I would just do a rebuild. Does this all sound logical, am I missing anything?

[mcfly]

not replacing the bearings is like reusing a condom, a set of ACL's would work great assuming your crank is within oem parameters and not ground. While the engine is out inspect the pedestal bypass valve just in case.


don't forget rod bolts too, just a little cheap security and will be easy since you need to crack the rod caps anyways.

[mitch32]

Thanks for advice. After pondering for a few days on what to do I have decided I will do a full rebuild. Since the motor will be out I feel that doing a rebuild is a good option, I don't reallly want to make removing the engine a hobby. Also this way I have the winter to do the rebuild, to take my time and do it properly, and my cylinder walls I'm pretty sure are still good so its an optimal time for a rebuild. I posted my rebuild options/parts on gtrcanada.com, check out the thread if you can and give comments. Heres the link: http://forums.gtrcanada.com/showthread.php?t=48305