So on Friday night i was going to the strip to do some racing. On the drive there I had looked down at my autometer oil pressure gauge and noticed it was only reading 40psi at about 6000rpm's. This isn't good as it is usally 100psi. I stopped at a gas station to check the oil level and it was fine, oil black and smelt of gas which was from multiple floodings. Found out my MSD box don't work with low voltage. On idle the engine was only making 20psi, normally it reads 80psi. I decided to drive the car back home as it was making some pressure.

Today I decided to dump the oil and check to see if i had any metal shavings to indicate bearing damage from the drive home. Thank god only oil came out. I replaced the oil and started the car and it was reading 40psi on idle. This is only because the oil is cold and i'm sure once it warmed up it would drop.

I'm running a FC front mount oil cooler and the line from the front cover to the cooler has pressure, however the line from the cooler to the rear plate I can compress with my thumb and index finger. Could there be a block in my cooler.

The other option i'm looking at is maybe the spring in my oil pressure regulator broke and there is no tension to keep it closed till it reaches opening pressure.


Any help from you guys would be great as i don't really want to open up my race engine that only has 1000km's on it.

 

The oil cooler has a thermostat in it. But even when cold and by-passing the fmoc, there would be pressure in the return line to the engine. That part makes no sense and I can think of no explanation other than the front line is a harder/stiffer rubber than the return line. You might want to change the oil again, this time draining the engine and fmoc. What weight oil are you running?

If you still have the old oil filter, cut it open and look for bearing shavings.

 

The oil lines are both stock FC lines. What if the thermostat is stuck in a closed position. I never drained the cooler and after running the engine it didn't have any real sign of the old oil from the cooler in the pan.

 

If the fmoc thermostat fails to open, the oil simply bypasses going through the cooling fins. It goes through the left end of the cooler from one hose to the other. There are 4 possibilities for low oil pressure. 1. The gauge is inaccurate, 2. Oil pump is worn. 3. O-ring between front cover and front iron is failing. 4. Bearings are worn.

What weight of oil are you using? Which oil pressure regulator are you using and did you increase the spring tension of the front OPR in the front cover? 80 psi at idle is quite high for oil pressure.

Since this is a new engine, did you replace any of the following:

Bearings
Oil pump
Oil pump chain
Housings
Oil pressure regulator
Oil control o-rings

What oil mods did you do?

What was your break in procedure?

Why was the engine rebuilt, (i.e., what failed on the old engine)?

 

I use 15w-40 oil.
the bearings are all new as i lost oil pressure on the engine once before and had to install new rotors, bearings and e-shaft (S4)
The housings are 1974 13B housings that have only seen carbon apex seals
The oil pump is a 85 12a pump - age of it and chain are unknown.
front oil regulator and rear were both shimed.
Rear regulator is a racing beat one.
My oil pressure gauge is a mechanical autometer gauge.


Why is it that i have pressure in the oil line from the cover to the cooler and nothing from the return line.

Didn't have much of a break in as this is only a race car.


Engine is a peripheral ported 13B
1974 rotor housings
1985 12A plates filled with devcon
1985 GSL-SE rotors
1988 S4 e-shaft
1985 12a oil pump
JDM FC oil cooler - came in with an engine my buddies shop got.

 

its easy to pop the thermostat out of the cooler and check it, but it really sounds like it blew the front cover o ring...

 

Did you do the oil mod on the S4 e-shaft? There are 2 you can do, did you do the mod on the front bypass spring? New bearings double the break in mileage. They actually take twice as long to break in as housings do with steel apex seals. I would have gone with a set of good used bearings.

Check the oil filter and/or run the engine a bit, drain some oil out and send off to a lab that tests diesel oil for contaminants.

When the front cover o-ring fails, oil pressure usually drops to zero. On my first test rebuild, I forgot to install that o-ring. After 6 hours of run time, mostly break in idling at 2k in the shop, I tore the engine down due to excessive smoking and no oil pressure. Had to replace all 4 bearings and the e-shaft.

 

Guys, Same problem. I pulled the motor out of my wrecked '81 and put in my new '84. Motor sat for like 6 weeks. After restarting noticed stock gauge had no pressure and pressures were normal before. I grounded the oil pressure wire and verified that the gauge did work. So I thought maybe the oil pressure bulb/switch. Just replaced it tonight and still no oil pressure. I did put a small dent in the oil pan at the front sump.Actually had jack on part of cross memeber and part on oil pan sump? I had used a product "No Leak" and it stopped my top o-ring leak you know by the 12a. Has new 10-40 mobile but didn't replace filter. I let the car idle for like 35-40 min because it hadn't been started in a while and the temp gauge stayed normal and didn't over heat. Soooo...ideas. I see the 4 things you said trochoid but....????? Thanks, Rob

 

Car has 128,000 miles

 

another cause of no or loss of oil pressure is damaged o-ring in the front cover.

 

Wacky, did you just wake up? Your the 3rd one to mention the o-ring.

 

coz I 3rd the motion lol

 

How long would it take to change front cover o-ring? Should I not drive it? This sucks?

 

dont drive it nor start the engine, i've seen this problem many times with people installing FC 6port motors to pre-86 RX chassis (all models). Depending on your "know how", it could take more than 1/2 day job

 

Its just too weird! Motors sits for 6 weeks,restarts with no oil pressure! Know how isn't the problem. Its taking all that crap apart again!!!!It doesn't make sense. The "no leak" would only swell the o-ring??? Think it swelled it apart???

 

could putting the dent in the front sump part of the oil pan have hurt the oil pump or broke off the pickup or something???

 

Before you start tearing into the engine, check/test the oil pressure gauge.

I don't think a dent that far forward on the oil pan would affect the pickup tube but don't count it out. I'd drop the oil pan, check the pickup tube and gasket, then check both OPRs. If those 3 check out, then it's time to pull the front cover. You will have to have the clutch pushed in and kept there before you break the e-shaft bolt loose. 2X4 wedged between the seat and pedal works fine. This is to keep the torrington bearings from slipping down and getting wedged. Do not allow the clutch to release until the e-shaft bolt is torqued back on. While the bolt is out, check the bypass spring in the end of the e-shaft and do the oil mod. You'll find a how to in the 2nd gen section.

Don't use Vaseline or bearing grease to hold the front cover o-ring in place. Either will cause it to swell. Use Hylomar to hold the o-ring in place.

Good luck

 

How do you check the oil pressure regulators? I guess its time to look in the haynes manual.

 

Peejay gave me an idea of my issue. I have been running solid engine mounts in my car for two years now and be mentioned that he had an o ring falure after solid mounting his engine from the front cover the the chassis. I think its time to get some poly mounts and rely on my RB torque brace.

 

could happen but I'm 100% not convinced. We've done 510/Corolla conversions with front engine bar that are welded directly to the frame with no reported issues

 

Not convinced solid mounts would do it either. If your looking for a torque brace, I have a brand new one.

 

Guys, I spent HOURS doing research on the site last nite. I know the condenser is there just to "dampen" any kind of noise or spikes. I found some guys saying that it effected the gauge and others not. I did find one post from a guy that said difinetively on three '84-'85 rx-7 and his that when the condensor was unplugged the gauge stopped working. There was a condensor on the '84 motor but the wire was ripped off. I do have the "extra" wire that was tied into the oil pressure switch in the '84's harness. SO...Like Trochoid said "don't rule out anything". Now I just have to get one. Rob

 

never rely on the stock mushroom shape oil pressure sending unit including water temp. Always use a mechanical gauges for a second opinion.

 

Found the issue. You guys were right. I blew out the oring on the front cover and i also lost a piece of the gasket as well. Time to fix it and get it on the dyno for a new year of racing.

 

Nice find! I thought I might have pinched a front cover o-ring in my latest build. But then I installed a mechanical gauge and found it to be right at spec pressure levels.