Hey guys,

Quick question. I'm about to fly out to look at an '87 Sport with only 35,000 miles on it. The only thing that has me a bit worried is the low mileage, knowing rotary engines don't like to sit. The car has a compression test of 124 psi front 128 psi rear.

Is there anyway I can get a better idea that this thing isn't going to blow up on me in 2 weeks?

I plan on doing all the usual things like cold start, restarting engine once warm after 5 minute cooldown, bringing to redline, checking oil/coolant. Is there anything I'm missing?

Thanks in advance.

 

Sounds like a comprehensive list of checks to me. I wouldn't do anything else. Strong compression numbers (Maybe verify with your own eyes?)

 

Not really missing anything. The compression sounds like a fantastic number, but that still doesnt mean that the car will crap the bed for no reason at all. Are you certain that it's a true 35k mile car? People can change odometers and the car is too old for mileage verification on the title. Pulling a carfax MAY find out what the mileage was if it ever changed hands, but 35k sounds like original owner territory to me.

You really can never, ever truly know if a car will hold together if it has been sitting and driven that infrequently. This is almost a 30 year old car here with fewer miles than most people drive in two years. The big issue is that all of the rubber and plastic on the car will probably be brittle and/or soft and worn out. Be prepared to take a scorched earth mentality and replace anything rubber attached the the engine. I'm talking fuel hoses (both tank and engine side), all of the filters (fuel, air, oil), radiator and all cooling hoses (heater, bypass, throttle body, etc), all vapor and vacuum lines, all fluids (engine, trans, diff, brake, clutch, coolant, and ps if applicable), the belts, thermostat, radiator cap, and front wheel bearing grease and seals. Be prepared to replace the brake hoses as well. If the car is rust free, which I would hope, you may be ok just giving it a huge maintenance overhaul. Be aware that there are two small heater hose sections in the dash for the heater core.

The big issue internally is the condition of the apex seals, springs, and oil control seals. Those are the seals that like to dry up and fail, as well as the coolant housing seals. Provided the engine is low mileage, you can buy a soft seals kit for reasonably cheap ($160-200) and replace all of the soft seals in the engine. The engine probably has 3-piece apex seals in it. They are not particularly desirable, but can be reused if they are not worn out. It's best practice to replace them with new Mazda 2-piece seals if the engine is apart. I'm not suggesting that you immediately rip into the car once you get it, but be aware that high oil consumption is likely and could lead to the engine needing a rebuild.

This probably does not ease your mind at all, but you are right to be cautious.

 

Not exactly what I wanted to hear, but thanks for the detailed reply. I guess I was just hoping that the car having good compression and no overt issues meant the internal seals are good.

 

Cold start video:

 

I bought an 88 10AE with 31000miles at the end of last season. So i am in the same boat as you. Just bring a powerful flashlight and look around real good. My car has a leaking rear diff seal. I bought new brake lines,rotors,and pads just because. I'm going to change every fluid in the car. need to change the belts. The hoses all look good from what i can see. I've seen them blow on 10 year old cars. So it doesn't really matter because unless you replace all the rubber under the hood you can't really have full faith in any of it anyways. For peace of mind. I bought my car and had a 4h trip home. Hit 80-90 mph a few times to clear it out. Car made it no problems. I say go for it.

 

Not really. The apex seals are electron beam hardened cast iron, and the springs are steel. Can't really "dry out".

As for the condition of the coolant seals and the oul control ring seals, its really a matter of how the engine had been run before, and how well it was stored.

 

Flying out this morning, still pretty nervous about dropping the coin. Might try and get a guarantee from the seller at least for the drive back.

If the apex seals are metal, then why do some engines fail in these situations?

 

What happens when metal rubs against a harder metal?

Theres the answer

 

That thing is clean. Can i have the interior?

 

Lol. Word.

If the car has solid compression, just keep an eye on smoke coming from the back of the car after its warmed up. This will indicate if there is an issue with the coolant seals or oil control rings. Also, might be a good idea to do the champagne test.

If everything else checks out, I'd say your golden.

 

Looks like a winner from the interior and startup videos.

I purchased a 12k mile car that had sat outside for 20 years and now has about 30k.
My big takeaway is that most catastrophic problems come from previous owners, not Mazda.
You hit the usual checks - Champagne, compression, hot restart, smoke. Check the date on the tires too. They may be past their expected lifetime.

Sitting engines can seize due to previously built up carbon and rust (mostly rust). This is more of an issue for engines that sat outside next to a firewood pile, not ones installed in a car.
If the engine is fine now, the metal sealing parts won't suddenly go bad on you.
The coolant seal life is a bit of a unknown. They may fail due to age instead of use. There aren't many data points on this. FWIW, mine are fine.
For peace of mind during your future years of ownership, it's highly suggested to replace soft coolant lines and vac lines. But they are not likely to fail during this particular drive home.

Metal doesn't rub against metal when it's not running.

 

Touche

 

what kind of compression tester did the guy use?

 

I would treat a high mileage rotary just the same as a very low mileage rotary. It depends on how it was driven.

When I bought my Rx7, it had 153,000 miles on the original motor. It had 2 previous owners, the first owner was a marine captain, and only drove it on the weekends. The second owner mostly drove it on the highway and racked up some serious highway mileage from that. The compression on both rotors was good but it was the rubber coolant seals that failed. Years take a toll on rubber. I lost a coolant seal one day and it overheated and cracked the front housing in 3 spots on the exhaust side. When the seal failed it started pressurizing the coolant and pouring it into the overflow.

 

Quick update: thoroughly inspected the car and it was as advertised. I was disappointed in the way it drove however and offered a lower price which the seller understandably didn't accept. So I'm going home having learned in a very expensive way that I don't really like the way stock FC RX7s drive. I like my 240sx more. Car felt numb and not very confidence inspiring. Could be old suspension, though my 240 is similarly old and feels better.

 

It is a base NA car with crap tires. That is pretty much par for the course.

When I got mine it was basically that car you looked at (with way more miles) with Racing beat springs, Tokico shocks and sway bars. It felt pretty good all things considered, but was still slow.