Cooling issue help please
 

My car is a 86 GXL with an engine that has been rebuilt in the past few years although i'm not sure how many miles are on the rebuild.

My issue is this:
The car ran fine until saturday. On saturday I was checking fluid levels and forgot to put the radiator cap back on afterwards because I was in a bit of a hurry. The car got real hot quickly but i pulled off the road. It had managed to spit and boil over most of its coolant. No big deal. So i refilled it and let it sit overnight because it flooded itself when that happened.

The next day, it overheated within a half mile of my house. Again it got real hot but i got it off the road before the temp gauge ever went out of the normal range. So i let it cool for a few hours and then refilled it.

The next trip, i was able to make it about 10 miles before I ran into problems. Again the coolant started to boil off.

I replaced the readiaor cap and thermostat with known good units from my other car. I was able to make it the 10 miles back home and it stayed at normal opp temp (right in the middle of the range) with minimal smoke right up until I pulled into my allotment and got on it a little. Then the low coolant buzzer went off and the temp gauge started going up. I parked it and let it cool. Again it was boiling the coolant but only for a few seconds.

Later I checked the coolant and it was only a little low (only enough to make the filler neck empty).

I can't tell where the coolant is comming from because the whole engine bay will be wet by the time anything happens. I check all the hoses and all seem to be dry.
The only one that I even suspect of being wet at all, is the heater core return hose where it goes from being a metal pipe to the hose on the radiator side.

I was thinking that it could be improper bleeding of the system, a clogged radiator or a small leak in the system that would cause the coolant system pressure to be released under load (again, I only run into any problems if I get on it after I have been driving for a while).

I wish i could figure out where all of this coolant is getting out at because like I said, everything will be wet and there is plenty of smoke from the coolant getting on the hot exhaust and engine as well as comming from the rad cap and overflow tank. It doen't help that the fan blows stuff everywhere.

Also, my car has no fan shroud but I rulled that out as the problem because when it overheated 10 miles from home i was going about 60 on the highway on a cold day in ohio. Cold enough to cool anything with that much windflow going through the RAD.

I'm renting a coolant system pressure tester from autozone tonight.
I am considering swapping the entire cooling system from my vert as it is getting a turbo swap etc sometime this year.

If you have any ideas or things to look out for while I'm working on it tonight or tips and techniques please let me know. I'm still fairly new to rotarys but I'm learnng quickly.

:icon_tup:

Nothing? Really?

i can't believe i didnt get a single response on this..........

First thing first, replace the rad cap or caps with new ones, the used one may not seat properly on the different housing. I would consider replacing the thermostat with a new one too (Mazda Brand)... just to take that variable out. Next, properly bleed the coolent system with 50:50 coolent:water mix at the strongest. And then see what happens. If the car was fine before you left the cap off and it didn't overheat then your coolent seals should still be ok and all it needs is to be properly bled.

While your working under there i'd get a fan shroud and put it on. If there is no belly pan on the car i'd get one of thoes and put it on too. Both are fairly important. The car won't cool properly at idle with the fan shroud and it won't cool properly at speed without the belly pan.

+1

I put the fan shroud from my vert onto the car when I swapped the rad into it last night. I'm not sure if the car has a belly pan or not, ill have to take a closer look. If neither of my cars have them how much do they usually sell for. I'm picking up a new thermostat today. I am using the caps from my vert now and it never had an overheating problem. I suppose i will just pick up some new ones to be on the safe side.

How much do mazda thermostats run? I will be passing by the mazda dealer ship on my way home.

i bought an oem thermostat from atkins roatry for 20 bucks, not a big deal.

Its no big deal.

No BIG Deal.



Stopped by the mazda dealership on my way home from work yesterday and ordered them.

Neither car has a belly pan. Anyone know where I can find one?

I have a 3rd gen and I know the coolant systems can be a pain to correctly purge all of the air out. I could be almost a week later and you'll be still be topping off the coolant. I put a bleeder valve on the top of the engine near the fire wall. When I'm filling coolant I'll open the valve to let most of the air out. It seems to work pretty good. You only need alittle air in there to cause the coolant to overheat. I would keep priming it. good luck

The undertray pan is a important piece i would get that on asap. Now as for your problem. Pull the spark plugs. what color are they? Burp the system again also, when running with the radiator cap off are there bubbles. Are they big or do they look like champagne bubbles?

With the cap off and the thermostat open while it is tunning it will spit the coolant out of the filler neck. The original rad dint have a cap on it and I think the filler neck up to is too close to the watep pump because once that water pump starts spinning that coolant wont stay in with the cap off.

I had not bled the system before becaue I could not find the bleeder.

I'll pull the plugs tonight.

What i do when i bleed my system is Take the radiator cap off when the engine is cold and start the car. As it warms up you will see the bubbles start coming out and when the thermostat opens you will really see them. do this until almost all ur bubbles have almost gone away.
this should solve your problem.

p.s. What thermostat are u running?

I had same problem.

The back of the engine block was leaking only when driving it.

Coolant was coming out of one of the main studs that hold the engine together, it was leaking between the transmission and block, found this out but getting underneath and noticed small stain on bottom of block.

I have seen tons of RX7s without undertrays and they don't overheat..my .02cents.

Bar's leak makes a headgasket repair. it has ceramic and carbon fibers..it works great..

2 bottles fix my buds RX7 and it had a blown coolant seal, and was overflowing the overflow in less than 2 minutes and would get hot.

Ordered the OEM thermostat the other day. Should be in today or tomorrow. I believe it was a autozone one before it. When I swaped in the factory thermostat from my vert in it lasted a bit longer. I also ordered new caps to make sure they are the correct heat range and sealing properly.

Hopefully this all works out so I can give my G/F her probe back.

Mine isnt leaking at all until it boils over though. Not a drop on the driveway.

Thats what I am saying, never found any water anywhere.

I really don't see a need for Mazda thermo and cap.

I have 3 RX7s and 1 has 450,000 and I never get any OEM stuff like that, it a waste of money I think..

A cap is a cap, same for a thermostat.. they either work or not.

I would check the water pump..then if you can't find any stains of coolant of engine.

The water pump deff turns at idle. I have watched it when the thermostat and filler neck were off. I think it slips at high engine speed though which is why i got the yoohoo belt.

I really doubt the belts slip.

You do know the water pump doesn't work after 4000rpms? it only cavitates the water and foams it up.

You can get a higher rpm water pump from Japan. The new pumps are a little taller with a biger impeller and different turbine fin shape.

Take the water pump off, I bet the impeller has been eaten away and the turbine fins are half or less than what they should be.

I have also had this happen once before.

As far as cooling is concerned always try and use Oem stuff. Radiator being the exception. The thermostat from mazda tends to work the best this will probably fix your situation along with bleeding. I have used the autozone brand and the car would do the exact same thing. So, do all the stuff i have listed and if you need any help feel free to pm me.:icon_tup:

can you link me to the j-pan water pump?

The waterpump looks new(ish) atleast newer than the rest of the car. I doubt it's bad the coolant really flows with the t-stat open. And if I pull it off and its good I have to buy a new gasket. And I'm poor.

False on the thermostat....Do a lil searching on here before you spout off stuff to people needing help. :scratch: :icon_no2:

Trust me man if it was the pump you would know it! :rlaugh: This guy is clueless.