1988 GXL. 166xxx miles. New rad. New belts. No T-stat. 2 Rad caps. (1 on rad, 1 on Tstat neck). 2 hoes going into the reservoir. Used fan clutch from another car. My problem is when im driving, my temp goes up (about 3/4) but at idle it goes down and stays down (about 1/4) . This problem has happen even with the t-stat on. Now I also noticed that the reservoir is getting filled up with the line that goes to it from the tstat neck. Any ideas?

 

any hot starting or cold starting problems?...do you always have to refill coolant every now and then?

if so motor might be on it's way out

 

No hot or cold starting problems. And no refilling of coolant. I changed a coolant hose bout 3 wks ago from the intake to IAC. I had to remove the throttle body to get to it.

 

one of the lines on the overflow tank should vent to the atmosphere. you dont run a line from the thermostat housing and from the radiator to the overflow bottle. you need to get the plastic piece without a nipple that goes on the thermostat housing under the cap.

 

No thermostat? Did you plug the bypass hole in the water pump housing?

 

no i didnt plug the bypass hole

 

My bro has a 7 too. We started to switch parts( fan clutch, tstat,) and still has the problem. My opinion is maybe im bleeding it wrong but idk how to bleed a vehicle with 2 rad caps.

 

I would assume that the fluid in the resevoir isnt returning to the radiator when the engine gets cold. Assuming that, you could have a pinhole leak that allows air in when the engine cools but doesn't allow water out when the engine is warm. I have had the problem befor and now actually have it again.

 

You need a thermostat. Having the bypass open while driving can cause the engine to circulate through the engine and not make it back through the radiator. Get a new OEM thermostat...

 

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UPDATE- so I closed up the hole on the tstat housing and hooked up the line from the rad to the reservoir. i also flushed the rad and the temp gauge isnt goin to the 3/4 anymore but it goes close to 1/2 witout the tstat. I called mazda and I gotta wait til Tues for tstat to come in. Now does anyone kno how to bleed the system wit 2 rad caps? I dnt think im doin it right.

 

s4's are easy, the top cap is the highest point on the engine. Fill it all the way up.

 

U mean the cap on the tstat neck?

 

yup

 

ok. i did that. i have it running wit the heat on to the top until it comes out. i rev it a few times and it goes down and then it gushes out.

 

lisle funnel. get one.

 

Do you have a undertray? That will affect your temps while driving roughly 15%.

 

yes i have a tray. im thinking my condenser is not letting air thru the fins in front of the rad. When i replaced the rad, it was full of debris and had like a gooey something on the fins.

 

Heres how I bleed mine. I got it from a thread on here.

Assuming the engine is cold:
Remove the radiator cap first, and fill to the top and replace the cap.
Loosen the small plastic screw by the upper radiator hose. You want to be able to quickly screw it in. A flathead screwdriver is the best tool for this.
Remove the upper cap and begin filling with coolant.
When coolant begins pouring out of the hole by the upper rad hose, tighten the screw.
Top off the coolant from the thermostat housing.
Start the car, and turn the heat on full, and let the engine warm up.
Watch for bubbles coming out of the coolant by the thermostat housing.
When the bubbles stop, put the cap on. You may need to add more coolant if necessary.

This process has always worked like a charm for me.