Hi, on my 87' TII I am having overheating problems, i have no visible/obveous leaks, i have check for the signs of blown coolant seals and have non of them (aka white smoke, bubbles under rad cap, exhaust feumes in filler neck). my symptoms are that my cars temp heats to normal and stays ok for a little while but starts blowing all of the coolant into the overfill bottle and eventualy starving the system for coolant. the only thing i can think of is that my thermostat valve is bad. does anyone else have any ideas? thank you in advacne

 

This is a fairly common mystery. It is caused when the coolant expands into the overflow, then for some reason does not return. After several drives, the radiator level is low and the car either heats up or the low coolant alarm goes off.

The coolant fails to return for basically one reason-as the cooling system heats up to operating temp, the hot coolant expands into the overflow tank. After the engine is shut off, the system cools and a vacuum is formed. This vacuum normally 'sucks' the coolant back in from the overflow, but if there is a leak that allows air to be pulled into the vacuum, the coolant will stay in the overflow tank.

It can be a leak in the tube from the radiator to the tank. It can be caused by using radiator stop leak; this stuff can plug the vacuum breaker in the radiator cap. You can have a leak around a hose that doesn't leak under positive pressure but does leak under negative pressure (vacuum). You basically have to understand what is happening, then troubleshoot until you find the leak

Start out by pressure testing your radiator. Pressure it up to about 25-30psi, That should find the leak. If you don't find a leak, test the overflow hose. I would also replace the thermostat and the rad cap with OEM only replacements.

I fought this beast of a problem for 6 mos or more. I finally found the leak as a crack in the plastic t-stat housing of the S5 NA. During the process of finding the leak, I converted my cooling system to an Evans Cooling zero pressure. I wouldn't ever go back to pressure.

You are going to be told that you need a rebuild. Don't believe it. Just find the problem.

Good luck.

 

yeah i have just about coverd the entire cooling system x-ept for the thermosat, the rad cap works because it pushes out (obviously) and i check it in the morning after and it does pull coolant back into the system, my problem is that it forces too much out and into the over flow tank and then makes the system low so it becomes insuficent to cool the car.

and this all happens in one drive (aprox less than 30min) not after multiple drives.

 

does it overfill the overflow and then you loose coolant because of this? it that what you mean by pushing to much out.

 

yes, the car seems like it want to push all the coolant out of the system into the overflow bottle.

 

That doesn't sound good. Replace that thermostat as soon as possible. Use a common parts store stat for a temporary help. Order an OEM ASAP.

Do the pressure test.

Also, you are using an efan.. Have you removed the air pump? If so, you need to add a double alternator pulley and run an additional belt. The water pump pully can slip with the airpump belt removed. This often leads to overheating.

Do you still have the plastic under belly pan and the air ducting tray behind the front bumper? These are critical for cooling at speed.
Especially with that FMIC.

Did it ever cool well after those mods or is this a new problem on existing equipment?

is there a recent mod that might affect the cooling or the airflow?

 

i have removed the air pump, but I dont think my water pump is sliping because i had it off when i still had the stock fan on and you could hear it squeel, this one you cant hear unatural like that squeel, and yes i have the belly pan on.

it did cool well before i did the mods (see signature), but i had a leak that i fixed at the same time i did all my mods.

O! i did take the tray off the top for the intercooler work and never put it back on. I guess i'll make one out of aluminum tomarow.

is the mazdatrix website thermostat = to a dealer part? i live in BFE michigan so its all the same to order one.

 

i dont think its the thermostat. i would test yours..boil the water see if it opens.Always verify somethings wrong before replacing it. You dont want to waste your money.. Anyway if the thermostat was stuck closed your car would overheat. but coolant wouldnt be pushed out. If it was stuck open then well your car wouldnt be overheating the problem would be opposite. How are you sure that the coolant is overflowing out of the overflow( hehe that sounds funny). Im guess you notice coolant missing. but do you see it pouring out of the overflow. Does your radiator cap relieve pressure to early? i dont know if you have a way of pressure testing it. to see if the water pump is working you an turn on the heat in the car if you still have the heater core hooked up. If it doesnt stay hot or get hot then your system is not flowing heat through the heater core. possible causes of the system not flowing.....you dont have the heater core hooked up. The thermostat is stuck closed, the water pump isnt pushing, or unlikly the heater core is clogged. Goodluck..hope you get this figured out

 

as for your mods im not sure if any of those would effect the cooling system. Yes adding more boost will creat more heat but i havnt heard that many people complain about the cooling system. Chances are though seens it started after you were messing with it something you did messed it up. I would try and back track from there

 

Thermostats can "just go bad". Fill the coolant system(with out the thermostat).Then do a coolant pressure test and see if it leaks down the pressure. Do not overpressureize the system then you will blow a coolant seal.
My 2 cents

 

yeah it was raining so tomarow i am going to take the thermostat out and test it, if anything i'll swap the rad caps w/ one from a parts car. and it over fills the over flow tank as there is coolant blown all over where the little hose hangs down for over flow, and you can watch it come out.

 

How long does the car sit between running intervals? Overnight only?

Do you ever add more coolant then what expands into the overflow tank? (unless it fills the overflow tank and runs onto the ground, don't count that scenario)

When you say "tested for coolant seal failure" what exactly did you do?

Mileage on the engine? And how are you verifying the overheating? Stock S5 gauge?

EDIT: I mentioned S5 gauge because you list S5 interior, however I'll bet its an S4 gauge.

Do you have any pics of the E-fan setup in the car? And will it overheat while cruising down the road at speed?

 

ahhh, it over heats all the time because it pushes coolant out of the system into the over fill bottle, it dosent start over heating untill the "add coolant" light comes on, there-en loss of coolant, my oil is not funny, there are no bubbles in the filler neck, does not burn any coolant (white smoke), and the coolant smells and looks normal. it over heat every were all the time after aprox 10 mins of driving, i have not external leaks, i have checked ALL (and i mean ALL) hoses many times. i have two things in mind: A) the rad is clogged or B) the cap is bad.

and yes it over fills the over fill tank and runs onto the ground. and it is a sock s4 gauge, i just swaped the black interor out of a s5 into my car.

 

Pressure test the system overnight, and try another rad cap.

It almost sounds like a toasted coolant seal to me. Only other possibility is a rad cap, and given the fact that its already gotten above temp. several times, the likelyhood its been overheated enough and cooked a seal is very high.

 

Of course it will! Where do you think the coolant goes when a car overheats?

Think about what you are saying.



There are lots of overheating threads with similar issues. Lots of times people struggle with cooling after an FMIC install due to the reduction of airflow caused by the FMIC, or by the cooling ducting (includes the undertray, the top tray etc) being left off.

Another common cause is an inadequate fan or a shroud that covers just part of the radiator. Just because it's 16" doesn't mean that is adequate for cooling the car. and if it has no shroud, it will be even less effective.

Have you checked the airflow direction? If the fan is installed as a puller but is pushing, that could be the trouble.

Also, if it is set to pull, is the fan blade on the right way? I seem to remember a thread that stated one of the Big Kahuna Fans that are famous for airflow have been coming from the factory lately with the blades installed as a pusher. They still move air the correct direction when wired as a puller, but the airflow is reduced very significantly.

'm still in favor of replacing the thermostat with an OEM only. And trust me, you never waste your money on a new OEM stat on a rotary engine.

Here is a question: Does the car overheat if you let it sit and idle?

 

i'm not sure, it doesnt idle so its hard to tell. i think the rad that i swapd in might be pluged, so i got another one to swap in today and ill go from there and report back.

 

just an update, i did let it "idel" and it overheats (1/2 gauge) sitting still, but before you say its the fan, the fins on the rad were cool to the touch and there seemd to be alot of presure in the rad hoses.

 

Have you tried any of the suggestions that were already given?

Like an OEM t-stat? Rad cap? Pressure test???

Not to sound like an *** but we've already told you what needs to be done. You just need to freakin' do it.

 

i went to take the t stat out and both of the bots for the filler neck broke so i said **** it and put it into storage for the winter.