Well after my last overheating scare I decided to flush the cooling system and clean it out. I emptied out the system several times adding only distilled water. When I got most of the coolant out, I put in Prestone Super Flush(32oz bottle) and more distilled water. Burped the system. So now that I'm running mostly water, theoretically the car should be running cooler. The flush instructions say to run the car 3-6 hours before draining. So I take the car out today shopping with the wife, gotta get some run time for the flush to work. "Ambient temp" mid 90's F, A/C running at full blast, driving on secondary roads, moderate stop and go traffic, after driving for 25 minutes the stock temp gauge starts to rise beyond midway. WTF? I open the windows and turn on the heat. After a minute the gauge goes back to midway.

I know both fans are working. Not sure about the ducting around the rad but since I'm in stop and go traffic and the fans are running, I assume the ducting is not that important. Dunno about the thermostat. Coolant blockage? Since the heat works fine I assume the flow is good.

Are any of my assumptions wrong? I've seen the same situation in stop and go traffic on hot days even before I started flushing out the system. Is the engine truly getting too hot, or is the stock temp gauge that inaccurate and I need to get an aftermarket one. Or perhaps one of the fan relays is bunk and not causing the fans to run in "high" mode when it's needed.

For what it's worth the engine was rebuilt 15k ago and the rad is OEM and only 2 years old. I plan on upgrading the rad, but I'd like to be sure the cooling system is working correctly before doing so.
So why is my FD running so hot?

 

It isn't good when your temp gauge moves beyond about midway or 'normal'. The car should basically ONLY come up to that max temperature, which should be about 190 - 210 degrees.
The fact that yours went higher than that and then came back down is worrisome.

My new engine and radiator (radiator courtesy of RADIATOR WORLD, a brass and copper OEM style) have been staying just awesomely consistent, even while driving in these un-Godly mid to high 90s and running the A/C. So this is about like what you were driving in.

I didn't see your mods if any....could you be experiencing a timing or fuel issue that would cause the car to just be running a little hot?

 

sorry if this was covered but did you replace your thermostat?

If not get a stock one.

 

Definatley replace the thermostat and pressure test the cooling system. What computer do you have? With most aftermarket computers you can change when the fans come on. Do you have the undertray on the vehicle? Sorry to say but start budgeting for a rebuild. That gauge moves beyond half and 9 times out of 10 you will have coolant seal failure in the near future.

 

Mod-wise I have all the bolt ons:
generic dp, RB cb, PFS intake and SMIC, GReddy elbow, plus a ported engine, and a silicone hose job.
A couple of months ago I got a EGR cel code( started to idle oddly) but the last time I checked I got nada. Otherwise the only issue is that I do seem to be running richer than usual and my idled jumps up and down( 700 - 1k) when there's a high electrical load. The idle issue stops after a while if the AC is on, else it's consistant. BTW, I'm already looking at the RadiatorWorld rads.

Stock ECU, running undertray and yeah, I'm pretty paranoid about a rebuild right now...

 

All that on a stock computer?

 

5 dollar fan switch. Not a bad idea to have anyway.

 

Yup, I rarely boost very high and never beyond 11psi.

 

Bad news buddy.

 

Hmmmmm....we have about the same in mods then. I wonder about your radiator. When you flushed it, did you get any crap out of it? I would try draining it again and putting in a 55% glycol/45% distilled water mix and seeing what happens. Straight water isn't going to cut it in that sort of heat, you could have started seeing steam spikes. Thermostat just might be worth replacing, but they either work or don't, usually.
Are your fans working properly, with the whole low/medium/high functions and all that?

 

Here's another thing to try. Carefully feel the radiator after the car has been running a while. Does one part feel cooler than the rest? Could be partially blocked.

 

When I drained it I didn't see anything unusual except for some dark globs that were also present on the dipstick in the overflow tank, exhaust??? No change in oil level or coolant on my oil dipstick. The fans work in so far that they turn on but I'm not sure if they do low/med/high. I suppose that adding the fan mod switch would let me know easily.
I'll go ahead and start flushing it again tomorrow and order a new thermostat. Hopefully I can get it installed, flushed, and burped before I go to NoVa next Tuesday. Else I'll be takin' the Outback...

 

Ok, add to the drama. The drain plug on the rad is stripped on the outside, so I can't take it off. I've tried various screwdrivers and no go. So I've been draining the coolant system via the bolt on the "block". When I do drain it that way the radiator is pretty much drained. The AST and thermostat housing empties and when I stick in a tube down the fillerneck down to the rad and start pumping it out, I only get a few ounces.

 

Dude just get a new radiator. Both Fluidyne and Koyo work well. Fluidyne is better quality.

 

Replace the t-stat, as suggested above. Only use the OEM T-stat!!

 

Actually I'm looking at the second one here:
http://www.radiatorworld.com/radiato...no=15107&cat=1

I've heard good things about this company.

 

Yes, they do work well, but so does the RADIATOR WORLD brass/copper OEM, and it has absolutely NO fitment issues, even though it is about 30% thicker than stock. And only $167 shipped to your door. Not knocking the aluminum rads mind you....just that I wonder if they are a good "bang for the buck".

 

I wouldn't screw around. Get a fluidyne. Flush the system and you might as well do the miata thermoswitch mod!

https://www.rx7club.com/showthread.p...6&page=1&pp=15

 

Whats better with a Fluidyne or Koyo is the increased capacity. Yea you pay more, but the stock radiator is barely adequately sized for the heat this car produces.

 

Like I said, I've heard good things about their rads and it's a good price. But I want to resolve major issues before I just upgrade the rad. I "talked" to Mahjik and he suggested replacing the thermostat next and go from there. So I guess I'll give Ray a call Wednesday for a new one and go from there.

 

hey man, my brother had a similar problem. be sure to check your coolent hoses around the engine. when we drained, flushed and filled, we noticed that the coolent lines were shot. luckily we had extras. the coolent line off the top of the filler neck that goes under the intake manifold wasn't sealing well due to a gunked up nipple. i think that when we flush our engines maybe some of the goo that forms in and around the coolent lines at the nipples may coagulate and seal better, may in fact get washed out causeing the lines to expand and contract. maybe that's causing your over heating problems. it fixed my brothers. just a thought.

 

I forgot to mention to position the jiggle pin at the 12 o'clock position.

 

Well, I got a new thermostat from Ray last week and today I finally got a chance to take out the old one. Boy did it look bad! Half of the outside of inner rubber ring was missing. Took the old stat and dropped it in a pot of water and set it to boil. Nada, it didn't open up at boiling nor on the way. Just to double check I dropped the new stat in the pot, she opened up right away. Now I just gotta install the new one, flush out the rest of the cleaner/washer, fill her up and burp!

BTW, is there any chance of the missing rubber cloggin up the coolant passages in the block?

 

The missing rubber will probably get caught in the radiator. If you are in a position to remove the radiator, you might want to remove it, and flush it out while turning it upside down. This way, anything caught on top should wash out.

 

Thanks Adam. Right now I really don't have the time to remove it. I guess as long as it gets caught in the rad I'll be ok for now.