hsv

Yesterday, I was driving through some hills in slow-and-go traffic (very little airflow to radiator and uphill driving). It was very hot. I was obviously scared about overheating, so I was checking the stock temperature gauge fairly regularly. I had driven about 5 miles through the hills and saw no increase in temp, so I was happy. Unfortunately, I looked away from the temp gauge for no more than 30 seconds. When i looked back, it was almost to the *white* line, almost all the way to the top. My heart dropped and I pulled off immediately.I let the car cool down for a long time. While it was cooling, I checked the engine bay up and down; no leaked coolant, no venting of the radiator caps, no leak in the radiator lines, no leak in the radiator...I couldn't find anything abnormal (although I didn't listen for coolant boil and it was just a visual check). After waiting a long time on the side of the road, I tried to start the car, unfortunately, my battery was dead from keeping the fans on. I got a jump start, and checked the exhaust color, it perfectly clear (no coolant burning?). I got in the car turned the heater on full blast, and slow drove home (not more than 10 miles). The car seemed to work fine, but I didn't push it, I was *very* easy with it. The temps never passed normal on the way back home.

I've left the car sitting overnight, hood up, and I'm scared to drive it. Maybe tonight, when the temps go down, I'll try to start it and see what happens.

My question is, has anyone ever seen their temps get that hot and not significantly damaged their engine? I pretty sure the gauge shot up, almost instantaneously, because it wasn't more than 30 seconds between when I check it at normal temp, and when I saw it at high temp. This may just be wishful thinking, but is it possible for the gauge to register high temps before serious damage is done?

Also, aside from a test drive and checking for leaks, what should I do to validate that my engine is or isn't damaged? A compression test? A coolant system pressure test?

Any help would be appreciated, thanks.

IRPerformance

iTrader: (41)

You won't know for a few weeks if its ok or not. If you damaged a coolant seal, it will start smoking white when started. It will get progressively harder and harder to start. You'll get low on coolant and have to add it periodically with no evidence of leaking. You could also have gurgling comming from the overflow tank. I would flush your coolant system, but in 80% distilled water and 20% coolant. Add a bottle of redline water wetter too if you like. Replace your themostat too. You can use a colder one which is meant for a miata.

hsv

I should also mention my CS mods:
Koyo radiator
Aluminum AST
50/50 Mixture with RL Water Wetter
New Upper and Lower Radiator hoses

RX7 8U

iTrader: (1)

I'm suffering too bud!

Check it out:

https://www.rx7club.com/forum/showth...48#post2147848

ZeroBanger

Hey.....

Listen over a year and a half ago I had issues with my cooling system till I eventually replaced my fans/ast/radiator and hoses. Anyway...

More than 1 time something dramatic happen and my water temp gauge went all the way to the white line. I always wondered ...did I damage my oring..

I never had any coolant problems and when I finally blew my engine when my mechanic took it apart he found NO damage to my oring at all.

Your car is designed to run in the white area of the gauge. Its not ideal to have it that high up and infact when it goes up there you have some problem, but as long as it doesn't go into the red *AND* your car does not go above 1/2 way regulary (gradualy over heating is bad too) you are fine...

Just make sure you watch your water temps, I saved my old engine about 5 times by constantly monitoring the temps...

hsv

Thanks alot David, that's good news
Let's hope nothing happen. I'll post my results after I test it tonight.

Also, everyone always talks about o-ring damage after overheating, which I agree, is probably the main culprit of engine failure due to overheating. But, what about the other components? Like, when an apex seal gets that hot, it will expand and wear unevenly, which will definitely cause engine failure. Also, what about apex springs? They're only designed to run at certain temps, over that designed temp, the spring will loose it's spring rate, right?

Anyone experience engine failure after overheating, but later discovered the engine failure was not due to o-ring damage?

hsv

Well, after a hard test drive tonight, the car seems fine. No apparent power loss, no difficulty starting, no smoke at start-up, no visible leaks, and no temp creep/increase. As if it never overheated.

So, what now? Does anyone think I should still get a compression test? Should I flush my coolant system, even though I just flushed it about a week and a half ago?

I'm inclined to just let it be. The car ran fine before the overheating incident, and unless it caused engine damage, the car should continue to run fine. I checked the coolant level, and at cold, it was almost full. Also, when I took off the TStat cap and the AST cap, there weren't any trapped gasses, which is good news.

So, no catastrophic engine failure for me!...today. Tomorrow's test will be the drive to work in late-morning heat. Wish me luck!

KevinK2

sounds good.

check for root cause ...likely leak in ast cap, through poppet valve, resulting in pressure loss with no external fluid leak.

assume u sealed airleaks around rad, and through sides of belly pan.

ZeroBanger

A compression test will detect a crack apex seal, but will not detect coolant seal failure or wear.

if your coolant seals are bad and your apex seals are good you will pass the compression test.

Later!

Jonesboro

I recommend that you do something to get more reliable engine coolant temperatures than what the stock gauge provides. The three most common choices are:

1. Linearize the stock temp gauge.

2. Add an aftermarket temp gauge.

3. Add a PFC with Commander (it provides for temp readout.)

spurvo

I wasn't sure from reading this, but have you done a fan mod yet, to where you'd be able to turn on your fans at will going up that hill at slow speed? I have that situation ALL THE TIME, and without the fans on low, the temp soars very quickly, just like yours did. With the fans on low, the temp (as viewed with a linearized temp gauge) doesn't rise more that 190F in 85F heat. Check it out if you haven't...

Note that running the fans low while going up a hill slow keeps the water temps down, but the intake and IC get REAL hot. Stay out of the throttle at the top of the hill...

ptrhahn

iTrader: (9)

Another thing to look for is puking/leaking coolant from the overflow bottle after shutoff. When my seals went, it let engine compression into the cooling system, and well after shutoff, a little puddle would form in front of the passenger front wheel. This will also eventually manifest itself in a coolant buzzer shortly after cold startup. Just pay attention for a while, and see how it behaves.

hsv

thanks

I'll check the poppet valve. I have had a digital temp gauge on the way, unfortunately, not fast enough tho. I've been meaning to do the fan mod, just haven't gotten around to it yet, but it's on my list.

Oh, and no puking from the coolant overflow bottle, checked that too.

And, the reason I was asking about compression, was because I'm not only scared about coolant seals, but I'm also scared about other damaged caused by excessive heat.

Nathan Kwok

The most direct damage from overheating aside form damaged O-rings is warped rotor housings. If that happened, you will know pretty quickly. Keep in mind the coolant temperature is only an indicator of heat on the housings, as 260F is nothing for the rotor housings. The problem is, when the coolant gets that hot it boils over and the localized temperatures shoot up way beyond that. That is why I advocate a 50/50 mix because it will allow you to overheat more before localized boiling occurs. Remember your exhaust gas temps are around 1300-1400F, and that doesn't bother the rotor housings one bit. I would figure out what went wrong though. You may have a stuck thermostat, or somehow the gauge itself may have gone crazy on you (although I've never heard of this).

Aristo

iTrader: (8)

If you are really concerned just get a cooling system pressure test in a week or so. By the way, does anybody know for sure what temperature the white line corresponds to.

RX-Racer

I just recently blew my motor from overheating! FAns
never kicked on and i didn't notice it. Pulled over and
fixed them . . . .thought i had it fixed but it wasn't! Then
2 days later got on it once all fixed . .. .Kabooom craked
the rear rotor apex seal. Looks like i got delicate and
beveled up and shot right out the exhaust luckly! Only
thing bad is the seal LUCKLY!

Well thats my story!

Jp