My old 87 was showing overheating symptoms. What finally fixed it? Would you believe the water pump housing? The aluminum casting behind the pump was eroded by the turbulence of the high revving pump and the previous owner using plain water for some time. The bypass valve seat under the thermostat had about a 4mm chamfer eroded away, and there was a 6mm hole eroded through the internal wall between the inlet and outlet side.
All this bypassing gives symptoms like a partially blocked radiator. I fabricated a repair with Bondo Marine Epoxy Putty Stick. That stuff is great..
1) MAKE SURE the thermostat FITS. The spring loaded disc on the stat must close the bypass port, or guess what? (it bypasses the rad)
2) Pull the water pump and the alumium housing and inspect the housing for erosion, especially the internal wall between the inlet and outlet sides.
Good Luck,
Bill

 

My car hs the same exact problem Ive posted a few threads b4 asking for help, nothing has worked, Ive replaced everything too, just like THe ACE has. Kinda pisses me off alot, cuz I cant drive anywhere, I know itll spew coolant. Maybe Ill chack out the waterpump housing.

 

The way I see it is that, if you dont get any white smoke, and you dont loose any coolant, then either its not the water seals, or the holes/leaks are so small that they allow only gas and not liquid to go through them...

I think it should be some hose, could be the water pump housing, or even the radiator itself ?

Damn, this is too much trouble for something so "simple" and "small".......

 

Does the problem seem to be worse with a lot of high rev driving? I know you say you don't have any bubbles or smoke, but that really sounds like something with the coolant seals; maybe a very small hole. I had a problem with my seals and had to keep my rpms low to keep coolant in the system. I could let the car idle all day long with no problems but couldn't go much above 3500 rpms unless I wanted to add coolant at the next stop.

Also, check what SureShot said to check. It's worth a shot.

Dan

 

Hmmmm, a thought that has crossed my mind a zillion times...its nice (or rather, not so nice ) to hear it from someone else....
So what did you do eventually with your engine ? I guess if you say that you found out it was indeed your water seals that you had the engine rebuilt ?

 

No, actually I had 162,000 miles on my engine and was planning a turbo conversion soon, so my main concern was just to keep it running until I was ready. I decided to use K&W Bloc Seal. It lasted 2 months with plenty of redline revs until the engine was pulled a couple of weeks ago.

Dan

EDIT: I did have to replace my radiator. I don't think I flushed it well enough like the bottle said.

 

OK, so any more ideas about leaks sealants ? Dont know if we have K&W (??) over here in Greece....

And whats the standard procedure on this ? Never had to do something like that before....

 

Directions will be on the bottle. Make sure you get one that requires you to drain and flush the system and wait like 24hrs for everything to seal. I tried to use a cheap one that was pretty much pour it in and idle for 15-20 mins and that was it. It only lasted 4 or 5 days (with no redline revs).

The K&W required you to pour it into the radiator, idle for 15-20 mins with the heat on full blast, and then to drain and flush the radiator. Then I had to leave it empty for 24hrs. Then it was fill it back up and go. Like I said, after I did that, I didn't lose any more coolant.

BTW, that is a drastic step, so make sure your seals are really your problem before doing that.

Dan

 

I'm not going to do ANYTHING until I get those ********* at the Mazda shop to check out my car and find out exactly whats wrong

"Yeah, we checked the car out, its fine, no problem, btw we changed the thermostat for no reason at all, just to charge you 60EUR for substituting a perfectly fine and brand new thermostat"

I think I'll go for all the coolant lines (3 on throttle body, 2 heater hoses, 2 main hoses from-to engine, and the small ones from-to overflow bottle). Rad cap is new, thermostat is new, radiator is flushed and not clogged, fan works (well, it does slip, but not much), only things that remain are the water pump (which works and -seemingly- does not leak) and the water seals

 

Why don't you pull off the water pump and inspect everything like SureShot said? At least do that before spending any money. Let us know and good luck.

Dan

 

Ok, why don't you make sure? go buy some of those strips you put in your coolant to test for exhaust gases?? This will tell you if the engine is toast..

I would also pressurize the coolant system after that and see if you can find a leak. and if it holds pressure.


-Zach

 

I'm going to drop off the car for an inspection. The head engineer there seems to have understood the problem (first thing he asked was if the car has trouble starting in the morning), but I told him no, and that I dont get any white smoke.

It could be what I have always suspected, and wan and WestJaxVert just said it as well: a very small leak in the water seals, which allows exhaust gases at high rpms to enter the cooling system, but does not let coolant in the engine...if this is fixable with some sort of sealant, then I would have to go down that road...


....I sure hope its a hose though, however I dont think so now...

 

????

Didnt know about that. Dont think we have anything like it here in Greece.....

As for pressurizing the system after a hard run, I thought about it, but cannt really do it myself. I'll have to rely on the Mazda shop

 

Well, do you have any auto supply chains?

They should carry them.. they are pretty common..


Any radiator shops? hell even the mazda shop might have some.. go talk to the head mechanic and ask to borrow some


-Zach

 

I live in Las Vegas (HOT PLACE) and was having similar problems after new water pump, thermostat, hoses, cap, electric fan, and coolant with water wetter.
WTF?
Anyway my problem was solved after cleaning oil cooler fins (clogged with dirt and old news paper debris)
AND
I found a a gasket was sucking air on the cooldown cycle, instead of allowing the radiator cap to draw coolant back in. Theradiator filler is bolted to my radiator, and sealed with a small gasket. That was the problem.

 

Check the alternator belt's tension, it also moves the water pump.

Flush your radiator.

Change the radiator cap, if it lost it's tension it will let the coolant go to the OF tank before it is supposed to.

If your hoses are collapsing, insert a big MF spring inside the new one to prevent it from collapsing when hot.

Check your timming.

Check the electric fan.

Rermove the thermostat and stick a piece of a broom stick in the small round hole in there...

 

Well, just did the "radiator-cap-open" test again, just to make sure....and indeed there are NO bubbles whatsoever. Thermostat closed and opened, but no bubbles came out...

So, either the leak is very, very, very small so that it only allows exhaust gases to enter the cooling system only at high rpms, or it is something else completely...

Guess I'll have to replace all hoses again, check the pump (although if the pump is malfunctioning I dont think it allows air to be sucked in), and indeed clean radiator, oil cooler, and replace as many gaskets as I can....

Rad cap is brand new, thermostat is brand new, radiator was just flushed, coolant just changed, so....???

 

ACE: READ MY POST ABOVE.

 

I did

 

Something is preventing the overflow coolant from being drawn back into the system. Is there some way to show that coolant is actually able to flow back thru the hose from the OF bottle (without sucking on it of course!). Maybe its only drawing air..?

 

how bout a new radiator?? and pump??

 

I had a similar problem with mine after i replaced the thermostat. i used new bolts and didnt realize that the housing has sleaves in the bolt holes that were the same size as the heads on the bolts i used. when the car got relatively hot i started to lose pressure and coolant out the housing. also, not to insult your intelligence, but are you refilling it properly-letting it run with the cap off until the upper radiator hose gets hot then topping it off again?

 

I hope that you are using genuine Mazda OEM thermostats/caps. I had generic ones fail after a couple of months.
Inspect the waterpump and radiator. Something is broken(impeller blade) or clogged(core).
Also, I had a radiator rust(salty air) from the outside in. All the fins(in between the rows) were brittle. The radiator was internally perfect but was breaking apart externally. Without the fins, the radiator couldn't radiate and the car overheated.
Make sure that you are running 50:50 antifreeze/distilled water. I am not sure about the weather in Greece, but you could try a higher antifreeze/water ratio. I like Prestone(yellow bottle) green antifreeze. It is the best for the money. And, I get distilled water at the local pharmacy/supermarket.
The cooling system should also be "burped". There should be no air in any of the coolant hoses.

Also, the cooling system is normally stressed in the RX7. The engine is oil cooled(10-20%). Check the oil cooler(bypass valve) as it might be clogged or bypassed. Make sure that you have good oil pressure. Eliminate the thermo bypass pellet. Excessive heat in the engine is taxing the cooling system. Look for other things that could cause the car to overheat. Is the catalytic clogged? Is the engine running lean/rich? Is it pinging/knocking(use high octane fuel)?
I do not care for electric water pumps. Too expensive and not enough of a benefit. My OEM Mazda water pump/thermostat have served me well. I hate the fan/clutch assembly. Test the viscous fan clutch. Make sure that the fan shroud is intact. You might want to try an electric fan conversion to prevent the engine from overheating.
The stock cooling system is marginal for a stock engine. A modded engine needs a better radiator.

These might help:
http://fc3s-pro.com/TECH/MODS/mods.html
http://www.unorthodoxracing.com/projrx7.html

There are a few places that can analyze your engine oil for antifreeze or vice versa. I think that the place is called oil analyzer or blackstone labs. This might help you with the problem. If the oil/antifreeze come up free of each other, then engine seals aren't an issue.

 

The water pump doesn't pressurise the system, it just takes care of circulation (the pressure comes from the temperature). I still think the pump is a suspect, and you should remove and inspect it. It's not a difficult job, and then you'll know for sure before ordering a new pump.
Also, I know you've replaced it, but when coolant is pumped into the overflow bottle but not sucked back in, it's often a failed radiator cap or the wrong one. Make sure it's a relief/recovery type cap, not just a relief one. Double check the cap just in case. A radiator shop will have a cap tester.

 

The Ace...

Still having the prob?

Damn.....do get the cap chkd. It is possible that you do have the wrong one...if it is the OEM one, then you should be fine...have them chk it.

Warm up your car, see if the top hose looks like it is puckering. If it is..then you have a leak somewhere. Sometimes when the system is hot..the bad parts will expand or tweet a little, causing a leak.

Good luck!