Temp Guage Rising at Long Idle and High Speeds...
 

1990 GXL; 5 spd; 3k on rebuild; intake; racing beat full exhaust; Koyo radiator

A while back I posted about my temperature guage moving from right below 1/2 to nearly 3/4 after leaving it idling for about 15 minutes outside on a warmer late winter day (60 F). Ultimately, I got a new exhaust system (thinking of clogged cats) that is racing beat and total free flow from downpipe to muffler, and I also put on a brand new Koyo radiator. Yeah, I laid down some cash. Guess what, same exact symptoms... I think my car is on a suicide mission.

If I drive around town a lot, and then stop and the car idles for more than five minutes, the temperature guage wants to move past 1/2. Moreover, if I'm cruising down the interstate, and the tac goes above 3200 (around 85 or 90mph), the temperature guage moves over half. As soon as I take my foot off the gas, it is as if it says, "Okay, just making sure you're paying attention..." and it goes back down below half. Also, another interesting point to note, if I'll slowly accelerate, reach a speed, cruise a bit, then let off the gas, coast a few seconds and raise the bar a bit (maybe five mph more than the previous cruise), I can climb to 100mph under the temperature guage radar. But, if I just go for it, he busts me every time.

Any ideas would be greatly appreciated... I hope the solutions are cheap. Its going to get warm here pretty soon, and when that happens, this problem has to be fixed or I'm screwed.

Car's cooling system isn't taxed at idle stock. Startto change things around and it might be though. Do you have an e-fan or clutch fan?

If you have an e-fan and have i wired through a temp sensor, it might be faulting and not coming online early enough to be effective for idle conditions.

If you have a clutch fan, you're still using your fan shroud (right?). The fan shroud keeps air moving through the radiator.

Also... I think when clutch fan is fail-safe (anyone confirm?) so if it wants to not work right anymore, it should be constantly locked up (always cooling best it can).

The only thing I have changed is the radiator... That's all. I put a new exhaust on it, but to my knowledge, that couldn't be considered part of the cooling system by way of an upgrade.

When the engine was rebuilt, a new mazda thermostat was installed, but a used water pump came with the engine. There are no coolant leaks anywhere. Yes, I am using the factory shroud around the clutch fan, and the clutch fan (stock) still seems to have resistance in it if I turn it when the car isn't running. It is also spinning at idle if I get out and check.

I don't understand what is going on. All I've done is replace a 14 year-old radiator with a new aluminum Koyo. I thought maybe that would solve the problem. However, the same symptoms are here that were also here before the new radiator. Temp rise at long idle; Temp rise at high speeds on interstate.

Temperature Sending Unit??? Water Pump???

You're not alone man. I am having somewhat of a similar problem. I flushed my radiator several times, new thermo and rad caps. Tested the senor...good to go. Stock fan clutch with shroud and has the resistance as well. One thing I did notice though and not sure if it's normal, on my initial start up I can after the fan blows hard for a few seconds and then settles down I can stop it from spinning with my hand and actually spin it the other direction. Now, after the engine warms up I can no longer do it, so not sure if that's okay.

Now as far as your used water pump.....I still have my original one on. Only thing I can think of besides maybe the fan clutch is the water pump not circulating properly. Book has a check on it. Says with engine running to squeeze the main upper rad hose for a few seconds and let go, water pump if working correctly will feel a sudden surge while letting go of hose slowly. With mine I can't feel a damn thing. I took the belts off and felt for play in the shaft, any resistance....and got nothing. So, best thing I can think of for the both of us, is to take off the water pump and inspect the guts and put a new pump in. Unless anyone else has any other advice??? Warmer and hotter days are ahead :eek:

could it be your running a little lean causing the engine to heat up a little..,

i had this problem once when i replaced a few hoses..
check all the hoses around the throttle body and make sure
there's no air bubbles in them...

happened in mine and i was getting the same symptoms

Can the water thermo sensor, if bad cause overheating when driving hard, but cool back down to the half way mark when easing up? Coolant looks nice and green, no air bubbles. Should I be able to see the coolant actaully move when cap is off and thermostat is open if water pump is circulating correctly?thermostat water thermo sensor

Give a good read to http://www.aaroncake.net/rx-7/cooling.htm

But your problem sounds odd....Slipping belts on the water pump? You ARE running the proper two belts over the pully, right?

Are you SURE you properly bled the system? Air pockets can cause blocks wich prevent coolant from circulating...

But it does sound like a water pump issue...how's the impeller look?

Update: After my car threatened me all evening at stop lights, on the interstate, and even sitting in the driveway once, I finally got fed up and went over him again. My exhaust hangers were a little off, and the time away from worrying about overheating was well served adjusting a low idle post exhaust install. But, after that was done, I revisited my 'issues'.

Yes, Aaron, I do have two belts on the water pump pulley. However, one belt is to my air pump, which is no longer viable. I have a straight pipe exhaust (racing beat downpipe to mufflers). I checked under the car, and all of my plastic is completely intact below the car. However, I noticed a large piece of plastic that was supposed to be blocking air from slipping between my nose and my air bay (oil cooler and ac condenser) had been knocked loose. He was hanging out sprawled across my lower grill. Now, I don't think I'm lucky enough for that to be my problem, but needless to say, I ripped that little bastard out with determined vigilance. I plan on going and getting a sheet of aluminum tomorrow and replacing the barrier that once kept air from going anywhere but the oil cooler and ac condenser, which was plastic.

I still think there is more, but I'll push it some tomorrow to see if that was in fact my problem. Also, my buddy brought his seven over, and although I do have resistance in my fan, his has much more.

If it runs hot tomorrow, I'm replacing the thermostat and water pump for sure. Any other suggestions? What about running lean/burning rich? How do I check that?

It's doubtfull that your problem is caused by an improper A/F ratio.

If you are referring to the plastic undertray, then yes, it is VERY important for proper cooling.

Are you losing any coolant? Burning it? Car pass the "bubble test" (search)?

Hey Aaron, yeah both belts are correct. Under belly pan is in tact. As far as properly bleeding system....that is just a matter of topping her off till she won't take anymore and opening the bleeder screw right?

All this overheating for me started after I changed my coolant a few months ago. Since then I have flushed the system twice and replaced all necessary items. But still the same dilemma. So I'm still thinking water pump, maybe impellar is worn out.

check your timming.

did you try pulling off the small coolant hoses around the throttle body and crankin the engine till coolant comes out??

do them one at a time from the line closes to the firewall around to the BAC and afte that

Hey, at the suggestion of a pretty sharp mechanic, I'm gonna install an aftermarket temperature gauge as soon as I can...

Can someone please offer me a cheap suggestion to accomplish this, as well some instruction? Will a universal temp gauge work from, say, Advance Auto (Sunpro)? How do I install a universal temp gauge? And, MOST IMPORTANTLY, once the temp gauge is installed, what are the temperatures that I should be looking for (cold, warm, and "new engine")?

Thanks in advance for bumps...

Getting Warmer

I also have a 1990 GXL..
My temp guage sits just above half on the guage.
Is this normal? Do i have anything to worry about?

Please explain more.

Remeber guys, I am only running hot when I give it some juice, usually in fourth. I slow down and it stops climbing. Could my fan clutch be failing at high speeds? I don't run hot when driving easy or sitting idle. But it is a definate change from before.

Apprecaite all the input fellas :)

my post was aimed to mathetas

Please explain more.


Remember guys, I am only running hot when driving hard, usually in fourth. Goes up to the 3/4 mark. I try not to let it get higher so I either slow down or bust on the heat to bring her down.Could it be that my Clutch fan fails at high speeds? Cause when driving easy, sitting idle or driving on cool nights I don't have this problem.

Appreciate all the input fellas ;)

the fan doesn't do anything while moving. it's for when you are stoped.

Wouldn't the fan be directing air into the radiator as well as blowing air on the engine at high speeds?

Exactly what I'm wondering. Cause I'm only overheating when driving hard in my case.

Thermostat.........
$18ish for the OEM one.

My car would run hot on the highway(I had an aftermarket gauage in) I could see the needle rising as I went faster.


The Koyo can't cool the water if your tstat is blocking the water from entering it.

Replace that anyways. It might fix it.

I replaced the tstat using one from Autozone. Is there really a difference guys? What about a tiny leak coming from the tstat housing, near the eyes? Could that small of a leak cause the high speed overheating?

Well everyone swears by the OEM ones.

I doubt a small leak would cause over heating unless you would take a lot of air in which totally ruins cooling.

I had a failing Tsta and would run temps of 220+ on the highway.

As soon as I put in a OEM unit I was running 180 daily no matter what.

Havik... I tried to pm you again, but the system blocked it for some reason. Anyway, dude, you should definitely go get a Mazda t-stat. It is less than $20 and well worth it - specifically designed for your car. If you can, I'd also think about finding another housing if yours has a hairline crack in it. You know that stuff will expand in the Carolina sun. Anyway, just lookin' out for a brother. I'll let you know how my new clutch fan works out ASAP.

I will add my two bits. Use an OEM and OEM only t-stat for safety's sake and get an aftermarket temp gauge.

An easy test. I think idle temp is ~~ 170 ish (mine atleast). When cold, remove rad cap, toss in the MECHANICAL temp gauge (the one with the copper tube thing with the thing at the end, not an electronic gauge!) where the rad cap goes (far down if possible). Start'er up, watch and learn.. No, nothing is going to boil over/explode (coolant does expand when it gets hot so you'll spill some a-freeze.). That would be your 17 dollar answer.

A faulty ground will do the same thing. Try this. While idling/doing nothing, turn on EVERYTHING electrical. If the temp gauge moves at all, grounds.. :D

I don't understand... Say, for instance, when I'm at a red light and depress my brake pedal, I notice the dash lights dim a bit, and even my idle dip and the temp gauge twitch... I've got bad grounds? How does that relate to my temperature gauge raising under specific conditions?

Please take the above in the vain it is intended. I just don't understand; I usually have to have things COMPLETELY explained or else I cannot understand.

Drew,

Hey man, not sure why the IM got blocked, but I will check my setup. So enough said, I'm sold. I will put in an OEM tstat asap. As far as the housing, it's in the works. One of the eyes that hold the bolt actually broke in half and the other bolt broke off flush with the housing. So needless to say, I had to do a little tappin and a little rigging plus some good ol'e RTV. But, still have some a-freeze sneaking it's way out. Might consider that guage as well. Apprecaite all you N/A homies inputs.

Drew, Let me know about the Clutch. I might take you up on that J-spec assy.

Goodlooking out fellas.

I found a clutch with 40k on it and threw it on my car tonight. Had to go to a buddy's to do it because I needed a better vice tool (stripped fan nut). When I got them both off, I really didn't see any difference in their clutch response. How could a centrifugal clutch be worn if it had resistance when you spun it - especially the same resistance as your replacement (at rest - not warm). I even told my buddy that I felt silly going through all this trouble with the clutch fan, and he kind of agreed. In a sense, replacing the fan was just a good excuse for us to talk about setting up a time to replace the water pump and thermostat. Anyway, got it on and drove it home (20 minute drive). I gave it all sorts of hell, and I'll be damned if the temp gauge didn't go past its common place. I was freaking out. Now, the outside temp was in the lower 50's, but still, I got it to get warm on the way up to his house, so I don't see how going home should be any different (maybe 5 degrees cooler). Then, to double test, I took my roommate for a drive about 30 minutes ago and drove it even harder. Hell, I was winding it out in every gear, and sometimes, I'd even sustain 4k and 5k loads for 5 and 6 seconds watching the temp gauge - nothing, rock solid. So, then I hit the exit ramp on the interstate wide open, and I held 4th to about 85-90mph, and as soon as I shifted into 5th, my gauge responded by raising mildly above half, but it then quickly fell back down a few seconds later. I turned around an exit down the road and repeated the procedure on my way back, but this time, nothing happened - solid read. So, as far as I'm concerned, the problem is a lot better, if not fixed altogether.

How does all that sound to you guys???

Havik, and anyone else having trouble with their t-stat housing, rx7world.com sells a new t-stat OEM housing and gasket for around 60 bones... Just thought I'd throw that out there.

Drew,

How confident do you feel about the new fan clutch? May you not want to consider a closer look when the summer temps get a little warmer? I'm usually fine when the temps are cool. Anything above 65 or so and I start having issues. Hey, another thing I thought of today was the possibility of the lower rad hose collapsing in? But then, would that be a blockage issue?Anyhow, I'll get up with ya later and talk more about it.
Thanks for the tstat housing link.

Later

Well, obviously every situation is different, and with the fan clutch, I feel like I did need a replacement - for good measure if for nothing else. However, your point about the warmer temps is well taken. Even still, I can see the temp gauge float, it just doesn't do it as much, and I can't induce it as frequently as I did before. Bottom line, I'm glad I did it, but I don't think I've totally gotten to the bottom of the issue.

I'm thinking that my belts are slipping at high rpm's. Why? Well, now at high speeds, as in cruising at 100mph, I don't really have an issue. It is in between gears and at the end of a wind that I see a response from my temp gauge. My next move is a dual alternator pulley and an underdrive pulley so that I can maximize belt grip on my water pump. Also, I'm running into some good prices on stuff I could stand to switch, such as a water pump (brand new - 50 bones). So, all things considered, I've already got a new radiator, and since the car has 147k and a new engine, why not replace the water pump, t-stat, belts, and pulleys if I can afford it? I don't need my air pump, and the mods I mentioned all maximize water pump performance.

You know, I might get in there and find out that something silly is causing the problem, but since I'm not losing any coolant, all my shrouding is in tact, and I've got a new radiator, a good clutch fan... Why not go for the t-stat, water pump, and pulleys?

I wasn't aware that you haven't replaced your tstat. Yeah man, take care of that first. Yesterday I adjusted my belts as well. Was afraid of the same mishap. It's been cool here, but as soon as it gets warmer, I am going to pay close attention to the gauge. See if that belt adjustment did anything. If not....OEM Tstat is going in there regardless. As far as the under pulley setup, I'd hold off until you take care of the basics first. You've gotten everything else straight, so why not take that ten minutes and pop in an OEM tstat. Then I'd go water pump. Who knows, the damn thing might be clogged with build up and it's flow is restricted. Either way bro, we still have some time to get to the bottom of this dilemma.

Peace

Good advice... I'll take it. How'd you tighten up your belts??? Never done that before.

Good advice... I'll take it. How'd you tighten up your belts??? Never done that before.

Good advice... I'll take it. How'd you tighten up your belts??? Never done that before.

Thanks, dude.

Good advice... I'll take it. How'd you tighten up your belts??? Never done that before.

Thanks, dude.

Sorry bout the double clutch.

No prob.
Belts....not sure what belts you have hooked up. I'm only running the alternator belt and the air pump belt. I took my power steering unit out and have the AC belt off for now. As far as tightening them, it's just a matter of loosening the alternator nut and bolt...the one on the alt mount bracket. The air pump has one bolt on top of the unit and one on the very bottom ( tight squeeze ) on the adjusting bracket. Just loosen them up and tighten the belts by putting tension on the alt and air pump until you have your desired tension in the belts, then just tighten them up. Might need another pair of hands to help out.
Anyhow, I did mine and it didn't make a diff. I was hoping it would, but not a thing changed. Worth a shot though you know. I am narrowing mine down to either a blockage in the system or my water pump. Let ya know what I come up with soon. Had a hot day here in NC, gauge was climbing fast without even pushing it too hard. I gotta be carefull.

I'll keep you and anyone else experiencing these overheating problems posted.

Peace

Did you install a mechanical gauge yet? You have no idea what the true temp is with the stock gauge.. I still say grounding problems.....

Grounding problems.....maybe for Mathetas's situation. I finally figured mine out tonight. I boiled it down to either the water pump or a major blockage. For those of you with similar problems. This is a must do! Start car to norm op temp, make a note of the guage. Next, shut car off and take fan shroud off, start car again and observe gauge, should see it start to climb. Shroud funnels air onto the rad, without it your guage will climb quickly. Now while you have the proper clearance without the shroud (still beware of the fan ) feel all over the rad, should have equal amount of heat exchange all over the rad. Mine, my pass side was hot as freakin hell and my driver side of the rad was nice and cold.....sign of blockage. To be 100% certain I put the shroud back on (not bolted, just placed on there so I can access the rad later) and took it for a 10 minute hard drive. After the extreme test run, my guage was at the 3/4 mark. I lifted the shroud out of the way (still running), and felt the rad once again. Same thing, hot as hell on the left and ice cold on the right. . Time for a new radiator . Anyone have any input on new rads? Where to get them and for how much....I am on a budget fellas.

Hope this helps for those of you with overheating problems. It was a damn mystery for me for a while. And thanks to all of you who gave me advice and info.

Peace

Man, dude... That sure is good diagnostic logic, there... Good to know you've gotten to the bottom of it.

I bought a Koyo (all aluminum) for $360. I've heard Fluidyne is the best, but that's all debatable. Anyway, I've seen stock rads (brass) with and without the plastic edges from $200-$300.

Havik... If you're in a bind for cash, I'd be happy to send you my old radiator (might need rodded out and cleaned, but no leaks) for the price of shipping. Honest. I'll even give you the measurements and let you find the cheapest shipping rates. I'm pretty sure I put it in the out building at my house at home. I'd have to go pick it up, but it's not a big deal.

IM me if you're interested, and we can work something out. Honestly, dude, I wouldn't spend a whole lot of money on anything but something like a Koyo or Fluidyne. So, that's why I'm offering. If I can save you money with mine right now, you can put some back until you can get a Koyo or Fluidyne.

Just an option...

I had the same temperature issues with my S5 TII, it turned out to be the clutch fan, although it felt fine it was stuffed.

Well... After spending a ton of money on upgrades and modifications... The answer landed in my lap for $15.

New Exhaust (Racing Beat) / Clogged Cats causing overheating...
New Radiator (KOYO) / Clogged radiator causing overheating...
New Water Pump / Not pumping enough water...
New Fan Clutch / Causing overheating...
Dual Pulley on Alternator / prevent blet slippage...

STILL HEATING UP...

Now, do you see anything missing??? Of course. It was something I certainly would have done first if the builder of my engine didn't downplay it as they said they put a new one in on the rebuild...

A Mazda OEM Thermostat.

Car runs in traffic and heat fine...

Oh, and by the way, unless you're planning on bypassing your air pump, which I do not recommend for S5 owners, DO NOT BUY A DUAL PULLEY FOR YOUR ALTERNATOR. It is useless. I found that one out the hard way too.