Firstly, let me say that the last two days has been one of the most beautiful and at the same time frusterating times in my life. I'm in a hotel right now, about 600 miles into, and 600 miles away from my final destination for driving the FD home.

I purchased a 93 FD (my first FD) from Upstate NY last night. We drove from Syracuse, through Canada, and are now in Port Huron, MI. We noticted cooling problems last night during the 7 hours drive.

About 3 hours into the drive home, I noticed the heat start to spike on the coolant guage in post <H conditions. I know how limited the stock coolant guage is, so I immediatly pulled the car over, opened the hood, and let her cool down. (I watch the coolant levels as much as my spedo...)

It seems we are leaking coolant, and can't keep it in the engine. We top the car off with coolant, but as soon as we put preasure in the system, it begins to leak a TON under the coolant overflow chamber. (From pass side of engine) We pulled into a dealership in town in MI, and their best mechanic tested the system for two hours. He is convinced that there is some internal engine problem, that is causing the coolant to become too preasurized, thus forcing it out of the system. He thinks the engine is toast.

At this point, the engine has not lost any power, runs incredibly strong, but can't keep coolant in it for very long. We can travel about 60 miles before the coolant is largly absent from the system, and the heat starts to climb. (At which point we would pull over). I'm not sure if this coolant leaking will get progressivly worse, or if we could finish our trip by just turing the 12 hour drive into a 16 hour cool-and-refill-athon.

I'm in the middle of nowhere, Port Huron, and my options are really limited. I can leave the car here, rent a car for 400 and drive 12 hours home, or pay 950, renting a 17ft U-Haul and 4 point dolly to pull the Rx-7 home...

I guess my question is this... The engine is likely suffering a blow seal, some internal problem. It will likely need to be rebuilt/replaced. I can accept this. Is it possible to drive the car with the coolant issue, as long as we keep the temperature sub 230 with the reduced ammount of coolant in the system? As long as the engine does not rise above the 50% mark on the stock guage, do I need to really worry about how much coolant is in the system?

In closing, I just wanted to thank all of you in advance for your help. It's just been one hell of a trip... my father is trying to rest in our room for a few hours to get some rest, and we are going to re-evaluate our options at around 7:00 central this evening.

-Ben Tarnowski

 

Does it have an aftermarket Air Seperator Tank? if so the cap might be bad allowing the coolant to pass by it into the overflow tank...go to any local auto parts store and replace it with a 16lb cap. they are only a couple of dollars, this has happened to me a few times.

 

Uhh ohh...

The stock temp gauge is totaly useless. By the time the gauge goes up its too late.

The extra pressure would be from a coolant seal.

Your going to need a new motor. You can try to limp home anyways because im sure the irons are warped.

I feel sorry your starting your rx-7 "career" out to a bad start.

 

Did yo check for cracks / leaks in the overflow tank?
Where specifically do you think its coming out of the tank?
Do you have any idea what kind of tests did this mechanic do on the cooling system?

 

I personally would never drive with reduced coolant in the system. Aside from a few air bubbles, it should always be 100% full. Carry a few gallons of distilled water and top off the coolant always.

Follow the others' suggestions for solving the AST issue. That should be functioning properly.

As well, the stock temp gauge is insufficient to keep you informed of dangerous temperatures. If the stock gauge moves, it's already been in dangerous territory for some time.

Perhaps you can get the info/parts/etc to install a water temp gauge or linearize the stock one for more useful readings. The water temp gauge isn't a hard install, but at this hour in an unfamiliar town it may prove difficult. Perhaps someone can suggest a way to run the system unpressurized to reduce coolant usage and make it sustain better.

Dave

 

Hello,

It does have an AST. I actually called Rx7.com this morning and I was informed that the AST was over near the battery. I initally thought that it was the AST that was cracked, but the leeks are over on the other side. At that point I ruled it out... was I incorrect?

The AST is preasurized correct, not just some overflow? The mechanic hooked up a coolant preasure system, and he said that as soon as the engine started, there was way too much coolant preasure leaving the engine, therefor an internal problem.

I had been up for 35 hours so it was difficult to understand him, also they wouldn't let me stay in the mechanics bay while they did the testing.

From what I read about the AST, when it cracked from heat, you lost all of your coolant and the system was compromised. Hell, thats pretty much what was happening here but I don't know much about the AST.

Again, facts are the leak is from the front passenger part of engine, and the car keeps coolant for some distance.

I would love for this to just be the AST, and not an internal engine problem. Which would be all the more reason to not try to drive it home and destroy the engine...

Thank you for the reply, hopefully somebody else can add some more thoughts too.

(If anybody has a few mins/ideas, I have a few bars of battery left on my cell phone. Shoot me a PM and I'll give you a call.)

Thank you again,

-Ben Tarnowski

 

Probably one of the turbo coolant hoses. It only requires a 10, 12mm socket on an extension to get to it, but changing it can be tedious and difficult. If the mechanic couldn't find it, you could supply him the info from the forum about this issue and he should be able to handle it easily. Bad engines don't leak coolant, they consume it. A leak is a leak, usually in these hoses.

Dave

 

I am under the impression that the overflow tank is not preasureized. All of the leaking is coming from over near the overflow... The mechanic was unable to tell me where the leak in the system was... and I can't find it myself.

He said he ran a test to determine the preasure of the coolant leaving the engine, my father said he hooked up lines and a sensor... and when he did his reaction was "Whoa, something is blown, this is way too much presaure."

When he wakes up I will ask him to tell me more about the test.

 

Dave, alright... So if the engine was pushing out too much coolant, or if the preasure was too high, I would never know it, unless there was a leak. Which there is.

I'm sorry I'm not making much sense it's been a crazy too days.

I was hoping he could patch the system for the short term. He just said he couldn't work on it, but there was a buy who does imports in town that could look at it "next week". Not even an option, from a time as well as experience standpoint.

 

sure it is not the rad side tank? external coolant leaks are not rocket science and any decent tech should have no prob. fixing it...

 

From what it sounds like, this mechanic has no clue about these cars and is probably just wasting your time. Do you know how to access the overflow tank from underneath? I'd wipe it down with a rag or something while the car was jacked up, start it and watch things to see if you can spot the origin of the leak.
Then I would take off the undertray if you have one and inspect the radiator and do the same.

I had a similar problem years ago and it just turned out to be a crank in the tank. I don't want to get your hopes up however because there are some differences in the descriptions of the problem...

 

The turbo coolant hoses are here:
http://www.davidgeesaman.com/rx7/DSCF0066a.JPG

Most passenger-side coolant leaks come from these overbaked hoses.

If one of those hoses is leaking, you should be able to replace it and stop the coolant loss problem. Either way, you or a mechanic should be able to find the source of the leak. If it's a cracked radiator, you might get lucky and find a local forum member with an old stock radiator to donate.

The coolant leak-down test only works to test an engine if the rest of the coolant system isn't leaking. Now as to whether you engine is damaged due to the overheat incident is still TBD, if you ask me.

Dave

 

Okay, keeping in mind that the stock guage is useless... which is widely accpeted, should I try to limp it home?

At this point I don't think the irons are warped, because there has been no detination, and no loss of any power whatsoever. Who knows perhaps it's already shot, in which case it's not going to matter much if I drive it home.

Heh, when the coolant levels got low, I noticed there was just alot of steam in the system (perhaps 50% steam 50% coolant) when we would stop. Is a steam/coolant mixture sufficient to keep the car cool for the highway drive home?

We are going to be driving at night, no sun. Is the air from the radiator + this steam/coolant mixture going to be enough to cut it...

I'm really on the fence, because it's going to be about the cost of a new motor if I leave the car here, have to rent to get back, and have to ship the car. I'm almost better off driving it and putting 3k into a new engine...

Thank you again for all of the comments, I have so much respect and appreciation for these forums it's hard to even put in words... :/

 

Dave, if it was damaged from overheating, would I know at this point? I know thats a tough quetsion.

Would it miss, would it have poor power, would it do anything? I'm just scared that the engine may be alright, and that I caught this early enough, perhaps it's just a leak with a hose.

There is defenitly a leak in the preasuried system somewhere, because when it runs, it leeks.

...

 

Irons can warp due to a single overheating episode. The coolant seals, if not damaged already, will soon thereafter be toasted because the warpage exposes them. I know I've heard of engines being 'ok' after a minor overheat episode, but I don't have the experience to comment how often or for how long.

You won't know really know about the engine until you fix the system leak and get it tested. Engine o-rings don't show power loss until they get really shot. Early on, you might notice a thick cloud of white smoke after restarting the car 'hot'. This is due to the pressurized cooling system having time to seep into the combustion chamber and build up, and burn off all very quickly. You should be able to drive the car home safely and evaluate that later if you get this leak fixed.

Dave

 

I was going to suggest that you drive at night, to keep temps down

Replace the AST cap as suggested above. Then drive it home, making frequent stops to top off the coolant. If you stay where you are, you may be replacing an engine that is perfectly fine.

Good luck

 

can someone link this to the local subforum? Maybe there is an experienced FD owner in the area that can swing by to help out?

 

Adam - just checking here - a bad AST cap causes coolant to push into the overflow tank, which then overflows to create the leak, right?

(The overflow tank leaks right there in front of the pass side wheelwell)

Dave

 

My friends 91 rx7 had a sudden coolant loss (as in instant trail behind the car while going 20 mph. and visually, we couldnt find the problem. But, after actually grabbing and givng each hose a squeeze, he was able to find a soft spot on the underside of the heater hose the had finally burst through. My guess is oil had been dripped onto it nad it settled at, and in turned softened the rubber hose.

Try checking all your hoses, especially where they attach to the engine.

Of course, I could also be totally wrong in my assumptions.

 

okay, one additional note:

I don't think there is a "leak"... what I think is happening, is that the engine is preasurizing the coolant too soon, and too strongly, and it's dumping out into the overflow tank... thats in accordance with what this mechanic said. It seems to purge itself so soon after startup...

It's this pumpage of the coolant out the radiator overflow tube...

I wish there was some way to run it home and keep it so cold it didn't need to expand. It probably has nothing to do with expansion of the coolant from heat, but increasued preasure from another failed component internally.

Thank you for all of your comments thusfar...

 

There is also a coolant line that goes from the ast across the bottom of the radiator into the overflow tank, this line has separate sections that just kind of push together and easily comes apart. This happened to me once and resulted in coolant leaking out over 60 or so miles. I finally found the problem, pushed the two sections back together, and everything has been fine since.

 

A failing coolant o-ring could also explain why coolant is coming out your overflow tank. Exhaust gasses will escape into the cooling system, overpressurize it, and force coolant into the overflow tank. A simple test for this is the 'champagne test'. When the car is completely cold take off the coolant filler cap (not the ast cap) and put one of those prestone filler funnels in it, start the car let the car come up to temperature at idle. (The purpose of the funnel is to keep the coolant from going everywhere). If you see a steady stream of bubbles you probably have a coolant o-ring failure. When mine failed it looked like the coolant was boiling at 50C and when the cap was on the cooling system would pressurize and blow all the coolant out into the overflow tank and the ground within minutes. Hopefully you just have a bad coolant line on your turbos or something like that but this is something you may want to test for given your description of the problem. Good luck.

 

This sounds to be on point... we are going to go test for bubbles right now.

(Back in 15)

 

I'll try to wrap this up, you guys have been so helpful... :I

If it is an O-ring failure that is over preasurizing the coolant system, is the engine already shot and needing a rebuid/replacement? I may as well drive it home if it is and save the 1500 on shipping/driving.

Lastly, my father wants to know if there is a way to depreasurize the coolant system, and run it home. Is there any way to have an opening and keep the coolant flowing?

Thank you again for your consideration... we are going to have to make a decision soon here.

 

Yes. If it won't hold the pressure, it will cause the overflow tank to overflow when the engine gets warm.