Hey guys and gals,

I have an interesting situation with an RX7 I purchased not long ago. Everything was running great when I got it. The boost pattern was normal and very smooth, no smoke, etc. Well a few weeks ago when I was driving it the low coolant alarm comes on. The car was not, and had not been smoking at all before this. I pulled over and checked out the coolant after letting the car cool a little and sure enough, it took about a 1/2 gallon of coolant into the filler neck. I had checked the overflow bottle recently, but admittedly forgotten to check the actual engine level. When I filled up the coolant bottle, a tiny bit of oil rose to the surface. Maybe a few drops at most.

So I drove the car maybe 10 more miles before it started smoking a good deal all of the time and the low coolant alarm came on again. At this point I checked the coolant level again and when I filled it up, a good bit of coolant/water mixture rose to the surface. I trailered the car back home and began to pull it apart to try and diagnose what has occurred.

Here is what I found:
1. The air filter and turbo inlet pipes somehow have an oil/coolant mixture all in them.
2. The turbo compressor housings are all puddled full of coolant/oil mix.
3. All of the intake tract has oil/coolant mix in it, all the way into the throttlebody/engine itself.
4. The coolant lines all have coolant/oil mixed in them.
5. The oil pan had a decent amount of oil/coolant in it.

So my question is: What would cause oil and coolant to mix like this in all areas of the engine? I have pulled apart the twin turbos and they don't appear to have any abnormal shaft-play, but is it possible they are blown and are allowing oil/coolant to mix? I'm really just trying to figure out what has happened so I know if I just need a new set of turbos, or a rebuild/reman engine. Thanks in advance for any and all help! I have searched, but could not find anyone that seemed to have the same issues as my car with oil/coolant mixing everywhere and even blowing back through the turbo compressors.

 

Sounds like you have an outer coolant ring failure. This will allow coolant to leak into the oil pan.

 

Yea, sounds like a coolant seal failure and it is time for a rebuild. Just dont let the engine sit very long without putting oil in the combustion chamber and cranking it over to provent rusting if it is also getting in the combustion chamber.

 

See, that's another interesting thing. After pulling off the turbos, I looked into the exhaust posts and spun the motor over by hand and the housings look very clean with no bad scratches or anything. There is no rust or anything like that. The rotors and apex seals look ok as well. What really confuses me is how did oil/coolant make its was into the compressor covers of the turbos and even backward to the air filter?

If I rebuild the motor myself would I just need a basic seal kit?

 

How long could it sit without cranking over? My car has been at a body shop for months and Im pretty sure it hasn't even been started once.

 

There is an oil vent line back to the primary turbo inlet. If oil/coolant is being pushed through it, you'll get some expelled by your BOV in to the airbox. This is what causes the track guys to use oil catch cans.

That depends on the condition of the other parts of your motor. Often times, the housings have warped or corroded around the coolant sealing area exposing the seal (which then fails). You really won't know what you need for a rebuild until you break the motor down and inspect every part.


If you want to verify you have a problem, drain/refill your oil and then pressure test your coolant system. If the pressure doesn't hold, drain your oil again before starting the car and see if you have any traces of coolant again (do all this without starting the car). If you find coolant in the oil pan, you have a coolant seal failure for sure.

 

Ok, now that all makes sense. I want to thank all of you for the incredibly quick responses and help. It looks like I will be pulling apart the motor to see what needs to be replaced.

 

If you dont have a coolant seal failure, it could sit for years and be fine. However, if you have an internal coolant seal failure leaking into the housings it can sit about 4-5 weeks before rust starts to set in. Let it sit more than 8-9 weeks and you can almost gaurantee your irons and rotors are trash.