DJGeQue

Ok here is the problem; one day my car just started over heating from that point on I haven’t driven it. At first I was told it was a blown coolant seal, but I past the bubble test. I don’t know if that means I don’t have a blown seal for sure or not but that’s the only test I have found from searching. Then I thought it was because I had an aftermarket thermostat which I put in about the same time as it started overheating. I put back in the old factory thermostat (checked in boiling pot seemed to open ok). When I turned it on though it still over heated and water was coming out of the cap on the neck. Also steam seemed to be coming from the general area of the radiator. One thing about the cap on the neck is that the seal is all warped. Could a bad cap cause over heating? Also can too much water cause over heating? Should I try running it with out the thermostat? Any help would be great thank you. Sorry if someone already asked this I did search though.

God Bless

vipers

iTrader: (8)

a bad radiator cap can definently overheat a car.... it hold the 13 lbs. of pressure that keeps the vehicle from overheating.... try that first...... also, make sure you 50/50 the coolant and water.... start the car with the radiator cap off, let it idle till it reaches operating temp.... then keep filling as the water lowers..... a vehicle can also overheat due to bubbles in the system... this will get rid of all bubbles! when the water stays at a consistant level, put the cap back on!

never drive a car without a t-stat..... keep it on........ if what i said doesnt work, check the water pump next......... it could also be bad!







note.... i know this because i was in the same boat your in...... and all it was was bubbles in the system!! but i replaced the cap anyways!

DJGeQue

Thank you... I am about to try that right now. I went to the Mazda dealer and they were closed unfortunately. Although I did remember seeing a cap in the bins in the back when I first purchased the car, I found it and it fit although it doesn’t look exactly the one I had on. The one I found has this spring sealer on it. My other one was just a cap with rubber. Was my old one the right cap or is the one found the right cap? Does it matter? If you want a picture of the two I can do that.

Thank you and God Bless

DJGeQue

Does anyone think using the cap on the left is a problem?

https://www.rx7club.com/attachment.p...id=99688&stc=1

https://www.rx7club.com/attachment.p...id=99689&stc=1

https://www.rx7club.com/attachment.p...id=99690&stc=1

Tiers

you need the one with the spring seal though there should be an overflow niopple that goes from there to an overflow tank. Do you have the 2 cap system though or just one. Cause if just one then you do need the spring type to relieve overheat flow to overflow tank.

jeeze does what I just typoed even make sense?

Tiers

clarify: if 2 cap system then rad cap is spring type fill cap is no spring. On some cars (mine included) there is only one cap on the filler neck with an overflow nipple to overflow tank.

DJGeQue

ok you lost me, I have only one cap on the neck, so does that mean i need the spring one or the non spring one?

God Bless and thx again

Tiers

then like me yes you need the spring one.. does it have an overflow nipple on the filler neck that goes to the overflow tank?IF not then you have a problem.

See, simply the spring one allows it to relieve pressure/overflow into the overflow tank. The one without a spring is for the 2 cap system like in the shop pic I posted cause the overflow one has the spring cap.

do you get it now or still confused

if you look at the shop pic I posted, although it has 2 caps, you can see the line to the overflow tank. On my car there is no cap on the rad so the spring cap is on the filler neck instead with a nipple to hose to overflow tank.

this could be your problem cause if when your car boils/overheats there is no where for the pressure to go/relieve.

DJGeQue

Ok I think I got it Tiers, since mine has a spring radiator cap then I don't want a spring filter cap? One thing that is not clear though is the overflow tank are you referring to the radiator sub tank? Another thing when vipers says “then keep filling as the water lowers,” what does he mean? When I put more water in the radiator the water goes up. Also am I suppose to put water in the filter cap or the radiator cap? And is there a method to know how much to put in?

Thanks a lot Tiers and Vipers

fc3s91

iTrader: (23)

Is this a S5 or S4? S4 86 to 88. The two cap system is only for the 86-87. 88-91 had one cap system. Have you tried to buy a new thermostat? Factory only!!!!!!. Also How many miles are on the car? I would have your radiator rodded out. It could be clogged. The other way to check if you have a blown coolant seal is, to check for exhaust smell of coolant or with the radiator cap off crank the car over and watch to see if water spits out of the thermostat housing with every compression. I hope that helped you out
Thanks Robert

DJGeQue

Ok, I have an 88 S4 so according to what you’re saying I have a one cap system? Or did you mean to say only S5 have the one cap system (seeing that 88 are still s4’s)? Sorry to have to clarify so much but what your saying to do is take off the neck (thermostat too?), while the radiator cap is open and look for water spilling out of where I took the thermostat off? It has 130k mi. on it so you saying I should probably swap my radiator?
Thanks

fc3s91

iTrader: (23)

No the 88-91 Have one cap system. S4 was one year to have one cap system. They got smart by then. Just take off the RADIATOR CAP only and crank the car over to if you have compression gases flow out like bubbles.
Thanks Robert

DJGeQue

Still over heating...

OK this is what I have done so far..

-Refilled the coolant according to FSM
-Put in factory thermostat and tested
-Did bubble test for bad seal and checked the exhaust
-bleed the radiator
-put in spring filter cap

Problems:
-Still over heating (btw whats a good temp to let it go up to?)
-coolant still coming out of the filter cap
-the reserve tank is at low (but no more coolant will go in)
-Also i noticed there is a black film inside my reserve tank although coolant looks clear.

Any advice could it be my water pump? Is there anyway to check that?

Thanks again

DJGeQue

bumpity

Schnide

does your car overheat quickly or slowly once it gets to op temp? did you check the fan clutch(assuming your still running the stock mechanical fan) or the rad for blockage?

DJGeQue

The temp increases at a faster rate once it reaches operating temperature, or I might say the temperature increases exponentially. As far as the fan clutch, how would one go about checking that? The same goes for the radiator blockage.

Schnide

if it is overheating fast you probably have a fairly big failure of some kind so the fan clutch is not the real culprit but you should check it anyways cause its easy spin the fan by hand when the engine is cold it should turn easily practically freewheel then warm up the car and spin the fan again(after you shut it off ) and it should have some pretty good drag to it

for the rad take off the fan and shroud(or leave it on and try to reach all the parts of the rad) warm up the car but be carful case without any fan at all it will overheat even easier than before and feel around the rad with your hand it (shouldn't be too hot if you turned the car off a short time after the thermostat opens) feel for cold spots which will indicat a blockage

try to fix the problem with the filler cap first. do you really have only one cap? i have an 88 and it has 2

DannyD

i had an 87 and before my koyo i only had one cap.

jhammons01

What are you talking about. there is a specific method for bleeding the air out of an FC and you didn't mention any of it.

Check out the archives for a thread called "filling the coolant after rebuild" Once you find out what causes your overheating issue and you fix it, your gonna need that thread.

DJGeQue

Ok so here is the latest report. The car takes about 4 to 5mins to get to reg temp and hits half way in like 8mins (sorry its not exact), so i would say it is pretty slow to overheat. There are no cold spots on the rad, but the fan seems to spin more freely after its warm. I spun it when it wasn't warm and it almost stop right after i let go, and after i warmed it up it got about 1 to 2 turns after i let go.

God Bless

xtremeskier97

Ive had 2 86GXLs and 1 86 base and all had only one cap. Ive never heard of this '2 cap system' you speak of. My dad also had an 86 base and only 1 cap.

When my current car was overheating after we got it going again, we kept going through the hose on the driver side of the engine by the spark plugs. Once we got that installed correctly and the metal clamp wasnt digging into the hose, we got the radiator serviced and checked for leaks and flushed. We also replaced the thermostat. All was well after that. When it was overheating...my overflow tank was always overflowing and squirting out fluid on the ground.

I would also check to make sure your clutch on your fan is working properly. That is something else we had to replace. Luckily...we had an extra one.

DJGeQue

Could no fan shroud cause the car to overheat? Because I don't have one?

Schnide

yes you need a fan shroud it is essential to get proper airflow through the rad as is the plastic underbelly pan. so if you don't have those get them back on your car first, then you will probably have to replace the fan clutch, mine was the same and i would have a really slow overheating problem in stop and go.

89tracerman

mine had the same problem so i decided to install a 16LBS rad cap and flushed the radiator and it never over heated again.
are you sure your radiator is not clogged up?