First off I did search, I found some things but none helped my situation...

I have been driving the car ('86 base model) for a little under a year now, no issues when I first got it.

It has the P/S and A/C removed, and a few other things done by the past owner. I myself just pounded out the cats due to them being clogged.

Anyways, the car sat for the winter ('bout 2 months or so) and I jus placed it back on the road in March, ever since the days have been getting to about 80 outside and the car is reaching the halfway mark doing about 80 on the highway to work, it has never gone over that at all, when I am in stop and go traffic it hits about 1/3rd.

I have searched through the forums looking for help in figuring this out, this is what I have done so far....

1) Replaced the T-stat with Mazda OEM - done

2) Flush and fill the system - Done

3) Check for any leaks and air bubbles in the system - Done

4) Water pump replaced - done

5) New rad. - Koyo Rad on order (almost done)

6) New hoses - Will be changed with the Rad.

So I am stumped, if the new Radiator dosn't fix this I need to know of any more options. Right now I am hoping its a bad guage, but I only have heard of the S5's having trouble with the temp guages (not saying it won't/can't happen).

I have also taken my friends advice and adjusted the a/f ratio for the day to see if it helps, and I got nothing.

The fan runs fine and it is working (at least from what I can tell) once I see the temp start to go down when I am stopped.

Also when I was searching I saw something in a post that confused me a bit. The guy said that for S4's the car is fine at 1/2 and don't worry about it until it gets up to 3/4 (or gets creepin that way) I have always thought it was supposed to stay at 1/4 and move to about 1/3 under a load (leaving a/c out since I don't have it)

I have even read the cooling chapter in the FSM and Haynes, that didn't help...

Right now I am going to get a new guage, I'll let you know how it turns out

 

Do you have the radiator undertray (big plastic thingy)?

 

Yup, forgot to add that, and the fan shroud is there too.

And I also made sure the SAFC was Zero'd out (got it back to stock settings) to see if running it lean was heating it up more than it should.

 

the rad should take care of it my car was running just like yours is now. put a good electric fan on it and that should take care of it

 

A "good electric fan" has nothing to do with it running hot when he's going 80 on the highway.