jetlude

iTrader: (9)

We replaced the thermostat, and the cooling system has been working execlent since. However, starting 5 -10 after shutdown is a problem.

I remember the aftermarket coolant gauge registering 240F, but the motor was shutdown right away and allowed to cool. We then topped up the coolant and begun the journey home, of course with an eye on the temps. The motor overheated 2 more times before reaching home, but was shut down each time at about 220- 230F and allowed to cool and then topped up with coolant. At this point we had no idea what caused the problem.

After overheating and cooling each time, the motor was very hard to start. Is this common? And now, when cold it starts right up but when hot, is kinda difficult. Will overheating affect compression, or damage the plugs or coils?

Mitchocalypse

iTrader: (2)

Not necessarily but overheating 3+ times will most definitely wreck a coolant seal. You're more than likely looking at a full rebuild.

Slow2k

iTrader: (9)

I don't like when people automatically suggest that every problem requires a full rebuild, I suppose there isn't much of another explanation. If it's coolant seals there's a product called Blue Devil which is a coolant leak sealer that people have had success with. It's available at most major auto parts stores but you might have to ask for it. We have it at ours but it's behind the counter. It runs around $80, but I feel it's worth a try VS. A full rebuild just over coolant seals.

bobsrx795

Is the nipple on the thermostat at the top. How did you bleed the air out of the system before driving. An air pocket can cause over heating as the coolant does not flow. There will still be coolant but it seems to act as almost a stopper.

Ceylon

iTrader: (3)

If it was a coolant seal it would be hard to start cold, rather than hot generally. Does it smoke at all after a cold start?

It could be as simple as the starter motor, if its on the way out, its hot performance will be where it shows it.

How did it sound when it was trying to start? A vid would possibly help.

If it happens again, make a few more stops and don't let it get so hot.

limepro

iTrader: (2)

I love blue devil, think it works fantastic but would never use it in my rx7, I have used it in other cars with great success just not tested on a rotary. just like it used to not work on the northstar engines and I doubt there is enough demand to test on rotary.

limepro

iTrader: (2)

to add to my previous post, I wouldnt jump right into the rebuild either, start testing. grab a pressure tester and hook that up to the coolant system, I got mine for like $60 at harbor freight and I have used it numerous times. if it doesn't hold pressure look for visual leaks or puddles. if none then pull the plugs and see if they are wet after the test. this would be a sign of a coolant seal. if it holds pressure then it is either air in the system or somethibg not wprking right.

jetlude

iTrader: (9)

The cooling system and seals are intact. The water seals was was the first thing I thought would be toast. I did a pressure test the following day since I have all the tools. The system held pressure. I have no wat plugs white smoke or coolant loss. The only problem is hard start after a run.

My question is, how could overheating affect compression, or could the excessive heat affect the plugs or coil or anything else that could cause a hard start when hot.

limepro

iTrader: (2)

I think I remember hearing of something with overheating and warping the housings but not 100% on that, do a compression test.

SA3R

Yeah next step would be a compression test to rule that out.

On hot starts (as it is heat soaked) you could have faulty items such as coilpacks (all at once unlikely) or starter motor.

If the starter motor is dying or unhealthy, it can rob more electrical power which does not leave enough for the coils to produce a good spark. I've had that problem on another car before.

jetlude

iTrader: (9)

Update:

The hot start problem is not nearly as bad now. Each time the car was driven and allowed to fully cool afterwards, restart after the next run was easier. In fact, we had no problem restarting after the last outing. We repeated this over and over to be certain.

My conclusion is that over a certain temperature, even with a healthly engine, starting may be difficult. On the run when the thermostsat went bad and the motor overheated, and most of the coolant was expelled from the the mortor through overflow. Even after refilling it will take many heat cycles (driving the car) to properly burp the all the air out. And with any air in the system, the temps will run higher than usual although it may not overheat. However, I have noticed that 10 - 15 minutes after shutdowm coolant temperatures would rise even higher than they would to about 245F . This is may be where starting may become a problem. And now that the system is properly burped, it only rises to about 225F after shutdown.

mannykiller

iTrader: (93)

There was damage done to the motor. If there was no damage done the motor would start with no problems. You shouldn't ever run the motor without burping the system anyhow. But the fact is that the motor got hot...and after reading your story I'm particularly concerned when you said that pretty much all of the coolant had been dispelled from the motor. That right there is just the kicker. That means the motor probly got damn hot. If the motor's not holding coolant you probly fried some seals. Which would explain the hard starting. Could've warped some components as well. I wouldn't run this motor... It would've been pulled asap and inspected. Look for white smoke while idling or driving.

jetlude

iTrader: (9)

Actually, its holding coolant just fine. I pressure tested the coolant system after the overheating event and it held pressure. At this point the motor is working as normal and hot starts fine. Still keeping an eye on it however.

Any changes I'll report back.

SWAT81

iTrader: (14)

when your car was not starting from the heat was there any ignition response or was the car completely dead with no response? Heat definitely is the worst enemy of our cars, with temps rising up to 115C~119C that is right before some serious damage. If everything seems normal since the incident count your blessings. Keep an eye on coolant levels each time before you drive as I had a small leak in my housing which required me to pour in 1 cup amount of coolant each time I drove.

Dudemaaanownsanrx7

iTrader: (23)

Hot start issues are normally attributed to low compression. But not always, and I wouldn't assume the engine is bad just because the car over heated even if it appears that its harder to start now when hot. Usually overheating causes the water seals to fail = coolant burning and white smoke. You are also more susceptible to detonation when boosting on a hot engine = blown apex/corner seal this doesn't sound like what happened.

In any case, it's good practice to do a compression test periodically to check the health of your engine. Especially if you're having hot start issues. A $20 tester will do just fine and is easy enough to do.

Here's a theory, maybe you warped an apex seal, causing loss of compression, the more you run it the more the seal gets smoothed out and broken in = compression normalizing.

jetlude

iTrader: (9)

After doing some more searching I just realized I installed the new thermostat with the jiggle pin in the wrong position. I put it in the 6 o'clock position. My understanding is that it should be at 12 o'clock, and this pin is designed to bleed air from behind the thermostat. At this point should I go back in and change it around? Could I just wait until the next time I have to drain the coolant since most of the air, if not all, has been bleed already.

jetlude

iTrader: (9)

Well, everything is back to normal. The car starts and runs like it should hot or cold. Not sure why it was giving hot start problems on the first day or two after it overheated. Probably what was mentioned in post #15 I did replace the spark plugs however.