I had the same problems myself..My car would run hot and I couldn't figure it out..My friend had the car before me..I bought the car because he couldn't figure out what was wrong..I will tell you what I did to stop it from overheating..Rx7s cooling systems are very tricky..One Aftermarket part and everything is messed up..In other words if you buy a thermostat from say Napa Or Autozone you run into problems..Not saying that parts stores sell bad parts..Just not Mazda specific parts..I replaced the Water pump..Didn't help..I bypassed my heater core...Didn't Help...Ran the car without a Thermostat...Still didn't help...So one Day I decide to go to the Mazda dealership and buy a Mazda Rx7 thermostat...Came home installed it...Put water and coolant in my system and wallah...It didn't overheat..Come to find out my friend went to local parts store and bought an aftermarket thermostat that was supposed to be for an rx7..It didn't work..Moral of the story if you buy parts for the cooling system..Go to the dealership and buy the original parts...It helps..

 

Have your mechanic check the coolant for presence of exhaust gases.. this is a simple test that any competent mechanic can do.. this will tell you if your seals are gone..

If that checks out fine, and you are confident that your radiator cap is correct and your waterpump is functioning, then check line going to the overflow tank (the whole line, including the line in the tank itself) if there is a crack in the line, then you will not draw coolant back into the system, it will only draw air.. think about what happens when you have even a slight crack in a straw and you try to sip your soda.. how much of the soda actually makes it into your mouth? this is commonly overlooked...

allowing you car to idle for 3 hours will not allow it to reach high enough temps for the coolant to be bypassed into the overflow tank.. the car must be driven.. if your car is maintaining proper temps after 3 hours of idling, you can probably rule out your waterpump and thermostat as the problem.

 

OK just an update to help clear things up:

1) All parts that I have on the cooling system now are stock Mazda ones (I even saw them in their little plastic bags ) Thermostat and rad cap have been replaced twice, both times with stock Mazda ones.

2) Its not a air pocket in the cooling system guys. Radiator has been filled and burped about a million times, and it always does the same thing. Gradually the system takes in air (or exhaust gases ) and pushes the coolant into the overflow tank. I then have to let car cool down, and return the coolant to the radiator by hand (although some times if I let the car over night it takes back the coolant by itself )

3) Water pump will be checked anyway. I'm thinking about replacing all the cheap hoses and gaskets again anyway, just to eliminate these two factors. There are 3+2+2+2 hoses all-in-all, and there are just two gaskets (water pump and filler neck). Am I right on this ?

4) About the other factors: the car does not "magically" overheat. I know the cause of the overheating: cooling system takes in air, pushes coolant into overflow tank, and thus is unable to provide enough cooling. The mystery here is WHY the coolant goes into the overflow tank AND stays there ? Is it because somehow air gets in the system (leak) ? Or is it because of exhaust gases (water seals) ? Thats the real question...

So although I'm fairly sure that the pre-cat is clogged, and that the oil cooler may not be at tip-top shape, the two cooling systems should be more than able to provide enough cooling as it is.

EDIT: I filled car with coolant last night (burped it, left it idling with open radiator to check for bubbles, and then filled it up). Today I came to work (a 40min drive), and checked the overflow tank. Same amount of coolant, no apparent loss (or overflowing) I guess this must be happening only with high revs and/or high temps...

 

Are you aware that a Technical Service Bulliten was issued in 1987 (TSB C3 -005/87) that covers coolant loss
(install air breather kit Number N320 15 S01A). This kit is no longer available from the dealer but you can order the individual parts. I have an 86 that has the same problem that you are having and I have the parts on order
I hope this helps, Get back to me
Sid

 

Already PMed you about this, and I also reply/quote to bring this up if anyone has any more info on this particular issue...

...anyway, car is in the shop right now, and I will be getting the news (good or bad) around noon

 

I'll help you, but I'm going to see the US game now, sorry.

 

1-1. Koreans did have it in them, didnt they ?

Just got off the phone with the shop. They were going to test the rad cap, but I told them that the cap is brand new stock Mazda one
Guy replies "so it should be an o-ring" They are going to test for exhaust gases in coolant, and I will have some answers probably tomorrow.....

****......

 

God damn man. You have replaced the hoses and cap five million times now.....give up on them!!!!!! Why don't you try some of the OTHER things these knowledgeable people have suggested!?!?!?!?!?!?!?!

 

I'm trying....but the guys at the shop keep replacing them ......although I told them that they are all BRAND NEW STOCK MAZDA equipment. I specifically told them to check the pump as well since the car is in there, and they said "no reason to, broken pump doesnt do that". Since I have a full time job, no time, and no garage, I cannt really do any serious work on the Rex myself...

 

Sounds like a pretty jack *** shop to me. Why don't you print some of these things out that these people have suggested and give it to the guys at the shop and tell them to look at that stuff.

 

Giving a list of things-to-check to a certified mechanic who thinks "He's all that" is a bullet-proof way to make sure that NOTHING gets done right on your car

You have to get it past him and make him think it's his idea... Anyway, since they will be checking coolant for exhaust gases, I think I will know for sure whether its a water seal

 

Does the main rad hose collapse on cool down??
Bill

 

Nope

Sure hope I dont get any exhaust gases in the coolant

 

sigh....
I could have sworn I suggested you take a look at the actual hoses that go to the overflow tank.. remove the one from the filler neck to the top of the overflow tank cap, and also the hose from the bottom of the overflow tank cap .. pressure test both hoses .. any pinhole leak or slit in the hoses will cause the problem you are experiencing....

 

I'm replacing them anyway

Just got off the phone with the RX7 guru at the shop He said that he did notice bubbles coming out of the cooling system, but veeeeeeeeeerrrrrryyyyyyyy vvvvvveeeeeeeeerrrrrrrrryyyyyyyy slowly (like one bubble every 9-10 minutes) The car was running at idle ALL day long yesterday, and the problem didnt appear (buzzer didnt come on). However I know for a fact that this happens and it happens faster when car is hot.

Only thing he did was replace the rad cap with one for 2bar I know this is A LOT of pressure, but he says it will help keep the coolant level where it should be (but I think this will put tremendous pressure on the internals of the cooling system).

Anyway, this is the latest update. I am also replacing the hoses to/from overflow tank. Anyone else knows about the TSB that Sid Weiner mentioned (1987 TSB C3 -005/87, Install air breather kit Number N320 15 S01A) ?

 

Although I know how bad you are feeling about you're car, I'm very happy with this thread. I have the same problem with my car (and shared pain is less pain). I've just replaced the caps and has ordered a new set of hoses at mazdatrix.

I also have to manually refill the cooling system from the overflow tank after a (+- 30km) drive.

My car also doesn't burn coolant and starts very strong.

The problem also starts when the engine is hot and I drive it at high RPM's. The problems aren't noticable when I keep the engine below 4000rpm. I did remove the termostat and that helped a little because the engine stays a bit cooler for some time so I can drive it a bit longer before I have the refill the coolant.

Actually I do think it is a bad seal, because the problems started after I did the ATF treatment (don't do that on a old engine!!!).

I've got some CRC copper block weld which I'm gonna try very soon( if it isn't a gasket leak it won't hurt ). That stuff is supposed to be the only sealing compound that should work on a rotary engine, it isn't available in europe but CRC was so kind to send me a few bottles.

I'll keep you informed...


Marco.

 

Hey Marco, nice (or rather, not so nice ) to hear you have the same issue...at least I'm not alone in this "boat"...

The problem for me appears much more slowly (I have to drive the car for almost 100-150km for the buzzer to come on), but I did a test last weekend, where I didnt raise the rpms above 4K. Same result, only it took a lot longer (went to pickup my gf, went outside of Athens, went for a coffee, and at the end of the day the buzzer came on). The mechanic in the shop also thinks it may be a seal, but it has a very, very, very small hole, which obviously expands with heat and accelerates the process.

Let me know about the CRC sealant (where did you get it from ?). I'd like to know about my options...

 

I can get such a distance but only on the highway, and I have to control myself not to put my right foot down to much. I do try never to get the buzzer, at every overheat there might be a slight enginedamage, so I play it safe and refill as I see the overflow tank allmost full. (the tank isn't bolted at the moment to make the refills easier).

I got the sealant from crc industries in the US, something like www.crcindustries.com.

Marco.

 

btw I removed all the cats and bought a straight pipe. That didn't make any difference for this problem, so you shouldn't worry about a clogged cat has anything to do with this problem. The car is much louder and a bit faster now.

 

Hey Marco, how do you perform the refill ? I will get the buzzer when the overflow tank is almost 9/10 full, but by that time the temperature/pressure in the cooling system is too much and I cannt get the rad cap off for at least 15-20 minutes (turn cap a bit, let pressure get out, close cap again, repeat). As you can imagine, this is not very helpful, easy or fast

And the site of CRC does not contain any info about the copper block...how can you tell its right for the rotary ? Isnt there anything similar in Europe/Greece ?

 

I searched for it a lot but I couldn't find any. I've tried the regular brands like holtz and valva etc. but that didn't help. The crc stuff is recommended by a lot of people on this forum, just do a search for it, there must be a howto somewhere on this forum.

When i do a refill I also have to wait for a 15-20min. I use the bleederplug to get the pressure out. Actually I do not use the car very much just about once a week for a little drive to keep the engine smooth.

Marco.

 

This is (one of) the thread(s) I mentioned :

https://www.rx7club.com/forum/showth...threadid=14859

It doesn't mention the CRC copper block weld, this came from varying threads form the 3rd gen specific.


Marco.

 

This actually lays a very thin layer of copper all around your cooling system. The guy says "if you dont succeed at first, pour another cup of CRC Weld and try again"

Anyway, my Rex is NOT THAT far gone, so I think I'll try something more subtle (like a normal radiator sealant), as well as replacing everything, to see if this helps...

Oh and btw, the rad cap is for 1,1bar, not 2bars . Stupid me for believing without seeing with my own eyes...

 

K&W Block Seal is what I used...Just make sure you flush the radiator better than I did.

Dan

 

Ace,

You can find more info about the TSB here

http://www.alldata.com/TSB/33/87330659.html

But if you want to read the TSB i think you have to pay, it sucks i know...

That is the best i can help u with.