Berserker

Ever since I have had my RX-7 (4 years and counting) I have always had this overheating issue. It happens once every couple of months and I cannot figure it out.

I have even taken it to RP in Garland and we have yet to solve it.

So far:
Replaced the thermostat twice
Upgraded the radiator
High flow cat, downpipe and exhaust
Checked fans, had to replace one two summers ago, but it did not resolve this problem.

It normally only happens when I drive the car for an extended period of time. Most times it happens I am able to crank up the heater and drive and it cools off right away. Today I was stuck in a drive through for 2 or 3 minutes, so I was unable to go anywhere...the guage went up to about 60 or 65 %. I saw it right away, cranked on the heater and got it back down to 50%, but even that is high. (and it is like 40 degrees outside to boot!)

Also...what is best for car when the temp starts getting hot?? Would I not want to continue to drive the car if it goes back down so that the radiator keeps the coolant flowing or should I shut it down.

I am just praying that when I get off work the bastard coolant light does not come one.

Next time I take to RP I think I will have them install a miata thermostat, but any idea why this keeps happening.

c00lduke

have you ever thought about switching to Evens NPG+. I plan on using it on my car after i'm finished this winter. I suposed to have many benifits over regular coolent but cost more. If you go to pineappleracing.com you should be able to find the link there with more info.


Thanks
~Luke

13brv3

I'll take a SWAG.

How about your fan relays? If you ever have the opportunity, such as when you were in the drive through, get out and put your hand in front of the radiator to see if there's air being sucked in by the fans. It's possible that you may have a bad contact on one or more of your fan relays, and maybe you're losing the fans intermittently.

When it happens, try turning on the AC to see if that helps. This will make sure the fans are on, and I think it bumps the speed up one notch.

Does it ever happen when cruising at normal speed, or is it strictly something that you get when in stop and go traffic, or drive throughs?

Good luck,

Berserker

I have had the fan relays checked and they are ok...

I tried turning on my headlights, but it did not do much.

..and yea, it only happens when I at a standstill..once I get moving, the problem goes away.

ZeroBanger

Listen,

everytime I read one of these "overheating" stories I feel obligated to return the help I got from this forum. If you have a good 5 or 6 hours you can do a search on my screen name and search term Overheat or "over and heat". Anyway, I have had every type of overheating problem you can imagine. Name it, its happened to me. All my hoses cracked at some point, my ast cracked, my overflow cracked, my fans died, replaced my radiator, etc.

I cant tell you 100 pct where your problem is, but if your thermostat is good (you should test it. remove it and put it in boiling water and see if it opens).

even on days that were cool, like 60 degrees if my car sat at idle it would overheat if I did not move. (im talking sitting for 5 mintues or so after its warmed up). It turns out my radiator fan under my stock mount intercooler got sandwitched between the koyo radiator and the radiator shroud. You cannot tell if this fan is bad without removing the battery to see it. listening or seeing if you feel the air moving will not work. Anyway had it replaced at a very good shop and on my way home my teps hit 105C on a 100 degree day. I never knew what water temps on an rx7 should be cause it always had this problem. through out the next 6 months, on a cool day it would hit 95 by the time I got home. One day it was 105 degrees out I went to sacramento to drag race and all day my car was 101C or so. at night when it was cool out (talking maybe 68C) my temps hit 114 and I knew if I did not get my car on the highway to get the wind, my engine was toast. It cooled down to 84C. the next day I found that the same fan that was replaced before was bad. Took it to the shop and he showed me the shroud had hit the fan blad causing the motor to burn out. This was mabye 2 months ago and my water temps never go above 90, and thats in stop and go traffic. In the mornings its at 82C and the afternoon around 85 to 86. I have the fans set to come on high at 90C.

I would spend 20 minutes take out the battery place on the floor and attach jumpers to the battery and the terminals in your car and then turn on the fans. A quick test is to remove the battery and manually try to move the fan. It may hit the shroud. The other fan is easy to see and rarely fails.

The other thing you may want to do is let the car idle and watch the water temps and see if the fans turn on like they are supposed to. Your relays could be bad causing them not to come on high. in stock form the high speed fans come on at 98 or 108 (cant remember which, but both are way to late).

I hope you find your answer I went through hell, almost lost my engine and finally got it working the way it was meant to work. when you find your problem PLEASE post back to the forum, you may be able to helpsomeone else.

PS: it sounds to me like its your fan not coming on or not coming on high speed.

Sidestick

iTrader: (1)

Do you check the coolant level every day before first start? These things have a way of letting coolant disappear without any leaks, evaporation I guess. You probably checked this before tho...

ZeroBanger

based on this it HAS to be 1 of these
1)1 or both fans dont work (probably only 1 failed)
2) fans not coming on high speed

when you move the air hits the radiator so it cools down. So it HAS to be a fan problem.

Berserker

ZeroBanger...thanks for the info...it sounds exactly like what is happening to my car. I will give it a look tomorrow, but I am pretty certain the fans are coming on and working.

As soon as I figure it out, I will let you guys know...thanks again for all the info and concern...

Sidestick

iTrader: (1)

That's why I asked about the coolant level. It will cool the engine with enough airflow even if the level is low.

spurvo

First of all, are you referencing all of this to the stock temp gauge? The problem with that is you have NO idea what temps are really being dealt with. While the linearization method does not give exact numbers, you get fairly close ranges to be able to discuss temp numbers. Further, you actually see when the temp is changing, under exactly what circumstances. My first advice here is to get some form of temp monitoring that is meaningful. Cooling back down to 50% could mean "down" to 215F (which is actually still overheating in my book!) or down to 177F, which is the thermostat closing temp. The point here is this is WAY too large a range to have meaningful discussions about temp rise.

Next, I highly reccomend a fan mod for you. You are seeing the classic temp problems that exist with this car. Remember there is NO cooling whatsoever when the car is stationary UNTIL the fans get switched on. Three minutes is an eternity in terms of temp rise, like you found sitting in the drive through (something I no longer do, even WITH the fan mod!). Further, it takes on the order of 5 minutes of driving at or above 15 mph to begin to get the radiator temp to come down through flow cooling. If you stop after 3 minutes driving, the temp has gone NOWHERE. Unless you have a fan mod. With the fan mod and a meaningful temp reading, you can tightly regulate engine temp, and never overheat again unless something fails catastrophically.

The next thing I'll mention is freeway driving. At freeway speeds, the cooling in the radiator is typically strong enough to bring the engine temp down to thermostatically controlled minimum, or 177F. At this point, the thermostat is closed, and coolant is no longer moving through the radiator. This means coolant is moving only slowly through the turbo housings. This means the turbos are heating the coolant temp to exhaust temps (450C!!)and this coolant is not flowing through the radiator. When you get off the freeway, I find it will take 3-5 minutes of ideling just to get the thermostat to open and flush the coolant into the radiator from the turbos. Then the temp goes up nice and fast! Thus the fan mod. Without these, you might find yourself overheating if you are on the freeway and slow to traffic crawl hell, or jump off and sit at numerous stoplights in a row. The turbo housings are dumping their heat, but there is no way for it to be removed from the system because you are not moving. Thus the fan mod.

I think it's happening 'cause the fans are not coming on when they need to.

edit- I need to quit wih thte long posts, huh? Started when there were two responses, and look what happened! Captain Obvious here...

13brv3

Here's an interesting post about fan relays you may find interesting. Just how closely were they checked?

https://www.rx7club.com/forum/showth...light=fan+fuse

Relays can fail intermittently. Contacts stick, or get dirty and sometimes fail to make a suitable connection. As intermittent as this has been, I'd check the fans as other suggested. If you find no problem there, I'd replace all the fan relays, and take a close look at the crimp connectors and wiring that go to the relays. Better safe than sorry.

Good luck,

ZeroBanger

One of my problems I forgot to mention is sort of what this guy is saying. Talk about an odd ball problem.....

I was running on 1 fan, had an appointment at rx7fasion to get my fan replaced in 2 weeks. I'd been running on 1 fan for 6 months so I figured 2 weeks is not a big deal. Anyway....

my temps were at 82 it was cool at night and I had just started my car after a long wait in the staging lanes. its not 87 degrees and I launch my car. 13 seconds later I look at my water temp at its 105. then its 107. I stop my car and check and my now my other fan would not start. It turned out that somehow, during that ill-fated run one of the plastic sleaves that contain the wires for the fan got a hole in it and pressed against the metal, causing a short. In this case my 60A fuse for my fans kept blowing. This is just another weird example of what can happen in a car that is cursed.

13brv3

Ha! Do we need to arrange an appt with one of those voodoo women in New Orleans? Make sure you bring a chicken

efiniracing

How about water to coolant ratio? are you running more than 50% coolant?

pedalpusher

iTrader: (1)

Another thing to consider is that the fans are controlled by a different temperature sensor than the gauges. The sensor that controls the fans is located behind the filler neck, kind of nestled in the rat's nest. Mine was totally gone because of heat stress, and had to be replaced.

--
pedalpusher

artguy

could i please sign up for the voodoo appt.

thank you

Im dealing with very angry demons. I douse it with holy water..garlic tuning...you name it...they dont go away. as soon as i think they are gone the bastards show up where i least expect them.

I have done research and I believe they are not of the same species of gremlin that haunted ww2 aircraft. Those creatures were herbavore. The ones in my machine are not only invisible but they devour the most expensive parts they can find.

any help would be appreciated.

I tried calling ghostbusters but they are out of business.


thanks


jason

ZeroBanger

I just drinks a few had too.

Chronos

you might wanna consider getting an aftermarket temperature gauge, it's prbly the most important gauge you should get...

djantlive

Also, you may want to consider replacing the radiator hose, especially the upper hose. The relay is what I would check again though. Basically, if you car is sitting in traffic for 5 min and you turn on the parking light, the fan should kick on, if not, your fans/relay aren't working.

jdhuegel1

I agree it's a fan problem.

Did you check to see if they are PULLING air? They might be going the wrong way..

Berserker

...but here is what I have so far:

The fans work fine, the problem is they are only coming on when the temp hits around 215 to 220 and then once it gets back down to 205, it shuts off. Of course this is not good, so I am having the car wired to have the fans runs all the time. (I so hope this fixes the problem). We narrowed down to possibly a bad thermo-sensor, but instead of replacing it, I just decided to go around it.

I am also flushing the radiator, when I had the fuel dampner replaced a couple of months ago, the car lost some coolant and I just filled it back up with just coolant so the ratio is probably a little off.

I am also installing a third party temp. guage to monitor the car, the stock one, as everyone knows, is crap.

I will let you guys know how it all turns out, hopefully I will never have to worry about my car over heating again.

...again, thanks for all the advice and maybe this will help others who are having the same problem I was...

ZeroBanger

for now take the plastic duct cover off and you will see a fuse panel underneath to the left. take out the A/C relay (not the fuse) and you can turn the fan on by turing on the a/c (the compressor does not come on) if you put it on 3 it will be on high.

spurvo

If you have your lights (running lights only OR headlight/running lights) on, or the heat up to 3 or 4, or the defrost on, THEN the fans will come on at 210F and shut off at 195F. If you don't have any of these electrical loads (any one of them will kick on the fans early) THEN the fans come on at 221F, and shut off at 195F. The thermo switch closes at 226F. So where your fans came on and went off would not be indicative of a bad thermoswitch, as they appear to have been working correctly.

Fans running all the time will cause the t-stat to run closed most/all the time, and this actually causes heat to build up in the turbo housings, might not be a great idea, but that's just IMHO.

I would do (and I did) the fan mod instead, as you can turn on the fan whenever you want to. You will of course need a gauge that tells you what temp you are at (or close to) so either install an aftermarket, or linearize the stock one (REALLY easy!). That way, the fans are off while on the freeway, where you should not need the fans to cool off (if at freeway speeds you cannot cool off with your radiator, you have other issues that the fan is only covering up for. Like improper blocking of the radiator sides) and it would make no sense to run them at that time. AND you can still turn them on when you hit traffic I think the fan mod is one of the very best things to do for this car, right after DP, coolant hose replacement (all of em!), AST replace, radiator replace, fuel filter replace, all fluids changed, plugs changed... right!