Zanity

iTrader: (1)

so in looking for an rx7 to buy i have come across this spotless 91 n/a.
its dirt cheap, even for a shell.
the guy says the coolant seals went bad a while ago so it will not run.
after a little research i find little on the subject.
what i do find though is that many people with this problem have the engine still runnable, don't know about drivable.

so my inquiry is this, can someone explain to me about coolant seals and if they are sometimes called something else?
can they be replaced by yourself or is it a procedure that should be left to the professionals?
thanks for any and all help provided.

joel_rx7

iTrader: (7)

Well the coolant seals (a.k.a O-rings) will ensure proper sealing and suppositely no leakage in your cooling system. You'll find quite a few of them when you disassemble the rotor housings. If they are bad you won't have an adequate cooling system i.e.
1_ you might have to put coolant every so often
2_ when running the car hard you run into engine overheat risk
Of course that all depends on how bad they are.

Here is a link to a video I like:
http://www.leechvideo.com/video/view458982.html

As far as replacing them, well you'll need to take the engine out, open everything inside, and change them. When you do that you might as well changes APEX seals and other thing to get almost a brand new engine (given the time it'll take you, if you have the means to do so).

Maybe there are some quick fixes if you know they are only slightly damage (maybe some other members will know about it) but I think that if you want to properly fix it, it won't be as easy as changing the oil.

That being said, I have only had my FD for 3 or 4 months so if people more knowledgeable than me have different opinions you should definitively listen to them

joel_rx7

iTrader: (7)

Now that I am thinking about it, there must be a cooling system test whereby pressurizing it at the filler neck with a special tool, you could tell how bad/good it is.

A dealership should be able to do that (that would not cost you a lot compared to buying a lemon), although it looks like they don't always know much about RX7s.

I'd contact one of them and see (if the seller agrees).

wankel1988

iTrader: (1)

It's all in what you're comfortable with any what your background is. I have worked on cars for nearly 10 years in dealers and when I bought mine and replaced the apex seals and pretty much everything else inside, it was a challenge to me. Not saying that bad, but I enjoyed the challenge and it's what I was expecting. You might can take it to a shop or a dealer, but they'll prolly not really know what to do with it, but if you find a shop near you that does some rotary work or a Mazda dealer with an old guy that lived through the rotary days(or going back through it), he might can give you some pointers. but it's all in what you want to make of it and how much you want to spend. I put about 1000 bucks into my car to get it running, and it wasn't in too bad of shape, so it's just really what you want and all. Good luck either way.

Zanity

iTrader: (1)

thanks for all the help.
it helps knowing that o-rings are coolant seals.

joel_rx7

iTrader: (7)

Well to be even more accurate o-ring can be either coolant or oil seals.

No worries, glad I could help.

dgeesaman

iTrader: (7)

Another explanation:
The rotary engine is a stack of iron and aluminum housings that create two combustion chambers. In each housing there are openings that allow coolant to pass across the layers and draw heat from the combustion chamber. Between each housing you will find an o-ring groove that surrounds these pass-throughs to keep coolant in the passages and combustion gasses out. The coolant seals are in these o-ring grooves.

The biggest problem is that heat from combustion is very close to the inner coolant seals, and in conditions of extreme overheat, the housings warp temporarily and expose the seals directly to the combustion gasses. Once damaged, combustion gasses can push into the coolant and coolant can push into the engine (usually after shutdown, when the cooling system is still hot and pressurized). Depending on the size of the coolant seal damage and direction(s) it's leaking you can see a variety of symptoms. So it can take a trained eye to spot coolant seal failure.

The best way to really know if there is a coolant seal failure is to test for hydrocarbons in the coolant or look for the tiny bubbles (aka the champagne bubble test). Other signs are excess pressure in the cooling system, hard hot starts (due to coolant that's leaked into the combustion chamber) and lots of thick white smoke at startup (burning coolant).

Like joel said, you need to rebuild the engine to change a coolant seal and there is not much point in doing all that and not replacing all of the engine seals.

Dave

joel_rx7

iTrader: (7)

Nice explanation Dave (and thanks by the way).

Is there an easy way to test for HC in the coolant by any chance?

dgeesaman

iTrader: (7)

I've never done it but I'm told there are test kits for it. It's probably easiest to pay a shop to run that one.

Dave

Zanity

iTrader: (1)

ah, makes more sense now.
on the subject of getting the whole thing rebuilt i can't really afford everything.
pretty much just looking at what it would take to get it to run.
maybe when i find another job, around next month.
until then thanks for all the help again.