The town that I live in is exactly midway between two "cities" (more like large towns, whatever), each is about 15 minutes to get to.

The larger one is where I got to work and school every day (M-F). The speed limit is 55 to there, so everyone does ~65-70. Every day, driving to and from there, my coolant temps never go above 1/4-1/3..

About once every week or two, I have to go to the smaller one to fix a computer or something. It is also about 15 minutes away, but the highway there is 65 mph, so everyone does 75-80. Every time I drive down there, by the time I get there, my temp gauge is nearly 1/2 way, which is worrying, but not critical. However, on the ride back, when I'm nearly home, the temps always go up quickly, it's never reached the red, but it's gotten damn close. probably 7/8 of the way up the gauge.

At that point, the coolant system is pressurized and filling up the overflow tank, and shooting steam, etc, etc etc. If I let it cool down (and refill it, after it dumps half it's coolant), it'll be fine as long as I don't do that trip again to go to work and school, as long as I don't make that trip again.

Here's the car's situation:
-I know that the radiator is boarderline junk. . I had it pressure tested/cleaned , and the shop said it has two small leaks, but that it should work okat for a little bit longer.

-I have no air pump and only a single belt pully on the alternator (For now), What does it sound like when your water pump belt slips?

-The water pump seemed fine when I rebuilt it, but I may have missed something..


Any ideas?

Thanks guys!

-I'm pretty sure it's not a coolant seal, as the engine was rebuilt ~6000 miles ago, and it does not smoke at all.

 

might be the belt is too loose. Try that and see if it works. also if you have a leak in the rad it will cause it to get hot. do you have your underpan on?

 

Well the obvious thing to mention is what you've mentioned. If your rad is only good enough that it "should work okay", then given your problem it is likely not good enough when the engine is under a higher load for a period of time.

 

Bukwild - I know the belt is tight enough (but not too tight).. I don't have my underpan on, though.. that basically disintegrated when I took it off.. I need to make one..

Snrub - I'm defiantly going to get another radiator in, probably a used one from the classifieds... I was thinking it was most likely the radiator too, I was just hoping someone had had this problem before and could jump up and down and say "There it is!" thanks

Anyone have any idea if my dad's 85 GS radiator will work in my FC? it's the same physical size, I haven't had a chance to check the mounting holes yet, but he's the only person with an Rx-7 that I know of within 4 hours...

 

There's a little bit of room along the radiator "mount" rails to maybe drill some new holes if the '85 rad doesn't quite hit the FC holes, but not a whole lot to play with. If you already have the shroud & crap out of the way, measuring hole centers from the top won't be hard.

You really need that belly pan, man, at those speeds

 

The biggest single factor at highway speed is the front lower & upper covers.

Nearly half the engine cooling is done by the oil cooler.
Without the under pan, ram air blows past it & not through it.

 

you know everyone says this and i believe its a urban legend.

Running an 89 vert na 50 minutes at 80 mph to work every day



- Ran without both and the temp gauge ran at a needle width less than half, which equates to 185. Drove it like this for a week. Needle never moved to a different spot regardless of blistering hot days or a rainstorm



- Added undercarriage shield and drove 700 miles on a weekend trip - NO CHANGE IN READINGS



- Fixed a/c and added top covers - have driven another 300 miles - nada





For those that will try to argue the gauge is not accurate, save the cheap effort to add to post count. we all know they are not accurate, however they will move when called to do so by sensor. This thing just does not move at all



with regard to oil temp, i have a gauge installed. that gauge stayed in place at highway speeds. Only deviated during stop and go where the shields are basically useless.



It is my opinion that the shields are there for protection from road debris, not cooling efficiencies

 

RE: the above
You are right - but..
Wonko has an S4 with some radiator pin holes, so it needs all the ram air it can get.
An S5 cooling system is more efficient than his S4, so your S5 will not be as sensitive to the lost air flow under the front.
The oil temp was more stable at speed with the pans installed. - My point earlier.

Sureshot - (Older than dirt also)

 

All I can think of is two things.

The rad that you have is clogged with ******* bugs, gunk and other ****, OR its clogged internall with lime deposits, or both..

 

I love when people say the same thing two different ways - love to agree!!!

The stability while important might not be his issue. I believe its a rad issue

 

yeah my car was doing the same thing so I just got a koyo and my problems are solved It never goes above 1/4 of the way up.

 

My grey '86 base has the best cooling system I know of.

It has a massive leak, so to let it run, we plug the hose into the engine coolant inlet and keep adding water.

It stays nice and cold.

All you would need is a nice long hose.

Then you could save weight by removing the radiator, water pump, and heater core.

 

I was having some problems running warm, and replacing my thermostat fixed it completely.

-=Russ=-

 

Everyone - Thanks for your comments I got really lucky. There is one rx7 in a junk yard within 50 miles, and it still had it's radiator AND it's an s4... so I picked it up for $50. Seems to be in good shape. I really do want to get a koyo or other fully aluminum one, but I've already sealed a deal for some Tokico Illuminas, along with new tires, and school, my budget is pretty well shot right now.

Syonyk - I replaced the thermostat when this all started happening... it helped, temporarily.. good idea, though.

Sureshot & Mr. Gadget - Thanks for the debate/comments. I'm working on fabbing a underbelly pan, even if it doens't do anything as Mr. Gadget suggests, It will help if my cooling system isn't 100%, and it will keep the dead animals UNDER the car, not in my fan...

Wayne - I'm working on it, I want to fab one out of some sheet metal aluminum or something... Or fiberglass, i'm not sure which yet.

I'll let everyone know how it turns out once I swap radiators.

 

You know you PROBABLY dont wanna be driving it when it gets to the 7/8 up range on your way home... On an s4 up to half way I heard is OK but anything higher and you begin risking blowing a coolant seal, especially at almost all the way up like you've done. If it gets this high you might wanna just pull over for a few minutes and let it cool down..

 

Actually, I started thinking about this after Mr Gadget's post...1/2 (or so) of the belly pan is AFT of the radiator, so if anything, all you would have to fab up would be something running from the OEM 10mm bolt holes in the front, to the bottom of the rad. This would be the important area to try to keep the "ram air" flowing where it is supposed to.

I run with my belly pan for a couple of reasons, the first being that it tends to keep the road debris out of the engine bay. I run without the "upper" shields, and with all of the OEM side foam crap gone, so there are many holes through which air can be diverted around the rad (using one for a little CAI passage), and she still runs at 1/4 or less doing 75 down the freeway (unless it's 100* out), and at less than 1/8 coming home at night...So, as Mr Gadget stated, that belly pan in & of itself may not be the cause of chronic overheating after all...But I'll keep mine on, just the same

 

I had the undercover off my car and at higher speeds i was running into some problems with heat now lets say i put it back on and i dont have anymore heat problems even up over 100

 

Yah I don't run with the underbelly pan either, or the top covers or anything and my temps are fine.

 

Lots of people who don't run the undertray report running a bit hot. Look at the car from underneath, the hole between the bumper and the angled bottom the the rad is substantial. The engine bay produces a massive restriction for incoming air and underneath the car is a low pressure area. Air will be sucked out.

Without an undertray you lose .01CD, so you're slower and use more gas.

 

Oh, I DEFINETLY pull over when it gets that hot, it's just normally it's near my house by the time the temp gets up that high.. it takes a while, and I can watch it slowly work its way up... Thanks for watching out for me, though



I'm thinking that the belly pan is a good idea, like I said.. I can't see how it can be a drawback, and I know it can be benificial... I just gotta get off my lazy *** and do it

 

Are you running 50/50 or what? I know its just a bandaid technique, but maybe trying running more of a water mixture with the antifreeze until you figure it out completely. That'll help things run a bit cooler.

 

Okay, I got the new radiator in two days ago (with that used one from a boneyard), and I got to make that run that always overheated me . This time my temp gauge never went more than about 3.8ths of the way up the gauge, definately below half way. On the back, i even spent most of the time above 80 (but never more than 85, my radar detector is good, but it's still a holiday weekend!).

dDub - Yeah, i normally run 50/50, but I was doing that (switching to water) as my temps got hotter..

Either way, I'm thinking this case is closed for now. All those who helped me diagnose it, (and helped convince me to spend the money on a replacement radaiator), I serioulsy appreciate it! Thanks!

 

proper ducting is the key

 

more gas - nope - measured this as well.

With all of my pontification I encourage belly pans to be used for road crap kicking up - however, its really not the casue of anyones cooling system problems, especially at highway speeds.