I've been having problems keeping my '81 rx7 running (https://www.rx7club.com/forum/showth...hreadid=146204) and have the following question:

When we got it fired up for the first time, we had it running for about a minute or so and my partner noticed the oil cooler spouting a stream , so we cut the motor and removed the cooler.
My question is this...we still haven't replaced the oil cooler and just have the holes in the engine casing plugged with bolts. Is this a bad thing? Would this cause it not to run? My partner says that it doesn't really 'need' it right now, but should replace it when we actually get the thing on the road...but then he's never worked on a rotary before...just the v8's.
Thanks,
JD

 

YES! Rotaries depend a great deal on oil cooling. I forget the #s offhand but it may do just as much if not more than the "cooling system". Probably OK for idling for short periods in the driveway, but any more than that and I would think you'd do damage.

Good thread on the subject.

 

Thanks for the link Heff...did a search, but didn't find that one. So...guess I'm in the market for an under-the-radiator oil cooler. Anybody out there have an operational one for sale?

 

There should be a couple at your local boneyard. They aren't that expensive, so you'll probably be looking at parting with ~$25. Look for a 79-82 model, as the 83+ moved to a really bad compact oil cooler mounted under the oil filter.

Good Luck

Matt
1979 SA22C

 

Don't run your engine for more than a few mins without the oil cooler... it's a critical component. Maybe you can get a rad shop to fix your cooler for cheap, or maybe you can find a cheap one. Either way, certainly don't go driving around like that.

 

Wow, this is the easiest question I've ever answered.
Do NOT run the engine without a working oil cooler. One-third of the rotary engine's cooling is accomplished by the oil system. -WG

 

Be sure to have the junk yard oil cooler sonic cleaned before you install it. You don't know what crap's in there. Only cost me 35 bucks for a 12a oil cooler to be sonic cleaned and pressure tested.

-bp-

 

I personally ran my first GSL SE from 1988 to 1994 and from 60,000 (bought it) mi. to 160,000 (sold it- big mistake) with no oil cooler. My rotary mechanic did not notice it was missing until he replaced the lower radiator hose and noticed I had a 12a radiator instead of the larger 13b . The car ran as well the day I sold it as the day I bought it and had no engine or other problems. I was just not aware it was missing. I am no longer so uninformed, but then it was just a fun car for driving and now I am restoring another one. I drove it on 10 hour trips to Florida 10-15 times. My oil pressure never got very high. When I bought my second GSL SE it had the oil cooler lines tightened too much and was leaking badly. I knew this and got a reman. cooler from the now liquidated Sun Auto Parts in PA. The lines were already new. I would not knowingly drive the car without the cooler, but somehow someone who had owned my first car previously had tied off or bolted up the cooler holes and I miraculously had no problems. I rarely had too much fun in that car and stayed under 5,000 rpms. I strongly recommend you get an oil cooler especially one remanufactured and strengthened at the cooler line connections to avoid aluminum cracks. I simply wanted to share my experience and in no way want to contradict the previous good advice.

 

You could try your own low-temp welding(soldering). Have you ever heard of Muggy Weld?

Another type of the stuff is Alumaloy.

You can use propane or MAPP gas with this stuff.

Wow, James, that really flies in the face of the issue. No-one had put one of the coolers that go under the filter?

 

My car was hit before I bought it (which I knew) and someone put the smaller radiator on it without the oil cooler! Unbelieveable. Then I put 100,000 more miles on the car. It drove great and you can imagine my shock at discovering along the way that the car never had an oil cooler.

 

Sorry for not directly answering your question. No, there was not any other type of oil cooler in an alternate location.

 

You must have just been real easy on it or something.

I know overheating is catastrophic but yet you read stories every once in a while where someone has repeatedly overheated their engine and they say it's fine.

Crazy anomalies I guess.

 

Matt: I'll keep looking, but where I live, there's not an abundance of rx7s in the jy. I did find an '83 (mine is '81) and have been doing some scavenging from that one, but no others.

DriveFast7: What the heck is sonic cleaning and where would I find a place that does it? Radiator shop? Maybe I'll just repair mine and get that done.

James: Sounds like you had some pretty good luck w/o the cooler, but from the majority of feedback here, I do plan on replacing/repairing.

Heff: Thanks for the links...once again That looks like some pretty cool stuff. The leak is actually coming from within the fins...do you think it possible to repair with something like that? Have you ever made such a repair?

Basically I was wondering whether my problem in getting it started was related to no oil cooler...ie some type of problem with too much oil pressure or something. If James had his running for so long without one, I would have to say that's not a factor.

I did put up a WTB post a while back and someone responded with one for sale for $60 (S&H included) but knowing the way mine is, have a hard time forking out the $$ for an unseen unit from someone I don't know.

Thanks guys....

JD

 

I wouldn't think the lack of an oil cooler has anything to do with the starting problem.

Yeah, it's supposed to be good for that. When I watched the Muggy instruction video this was one of the examples they had. Well I think it was a radiator, but they just pushed the fins back around the area. That could be a little tricky with the heat dissipation.

I think you're actually better off getting a good used one. That solder is expensive and takes some practice.

Best of luck.

 

I read in Mazdatrix catalog that the non mazda aftermarket oil coolers are pretty worthless as far as how they work. The dealer priced a new one at $575 for me! Find a good one off of a salvage yard and have a machine shop strengthen the line connections on the cooler so it will not break easily and you will be set. Follow the previous advice for sonic cleaning also, etc. Regardless of my previous experience I believe the cooler is crucial.