'86 GXL Auto. stock

I've been working on this car for some time. I bought it not running and have had to fix a few things. I've had several 1st gens but this is my only 2nd gen.

All coolant hoses have either been replaced or checked thoroughly and hose clamps replaced. The thermostat is new from a parts store(not mazda) and the fan clutch was replaced 3 times with used ones until I found a good one.

The car runs/starts fine and the temp stays around 1/3.....for a while

once the car reaches norm. temp. it slowly starts to "boil" or "blow-out" air and coolant into the res. untill it eventually overflows....then the temp. starts to climb more and more. If I use the A/C it happens faster.

I don't see steam in the exaust (I have a modified 12a which has done this) and the coolant does get sucked back into the system while it's cooling (after turning it off)

Initially I was using 50/50 Ethtlene glycol/water but added a little more ethylene glocol (probably 60/40 now) this didn't help.

What should I try next? (Really I just want to learn /fix what's wrong and then sell the car) https://www.nopistons.com/forums/pub...R#>/unsure.png

unfortunately it sounds like you have a broken coolant seal...... and its burning off the coolant. you can get a tester to see if there is exhaust in the coolant. i would check that first so you don't waste anytime. i hope it's not the coolant seals :(

Wouldn't I also get steam in the exhaust?

Why would coolant get expelled thru the overflow and not just exhaust gasses?

if its only a little bit wont' steam yet....

would it have anything to do with the radiator cap being located in the original position above the thermostat/ not on the radiator...

..or... that the generic thermostat doesn't have the jiggle pin that the mazda one has?

i'm not sure. you don't have to use a mazda cap but it can't hurt

i'm not refering to the cap but rather the thermostst itself--the mazda one has a jiggle pin and the generic one doesn't.

also for '86-'87 the is a service bullitin 07/87 about relocating the rad cap and source for the overflow---these mods hanen't been done to my '86 but...are ther truly needed?

i'm not sure. j9fd3s can surely answer this question https://www.nopistons.com/forums/pub...DIR

Get the Mazda thermostat and see what happens from there. vosko is paranoid about coolant seals because he puts acid in his cooling system. https://www.nopistons.com/forums/pub...#>/biggrin.png Alot of the aftermarket thermostats don't have the same opening characteristics as stock thermostats.

Get the Mazda thermostat and see what happens from there. vosko is paranoid about coolant seals because he puts acid in his cooling system. https://www.nopistons.com/forums/pub...#>/biggrin.png Alot of the aftermarket thermostats don't have the same opening characteristics as stock thermostats.[/quote]

so far i'm 3 for 3 on coolant seals. the only engine that didn't have bad ones was the original TII engine that broke a few apex seals https://www.nopistons.com/forums/pub...DIR#>/wink.png