Overheated, dumped all my coolant, no leak?
 

My RX8 was in for it's MOT yesterday. They revved it up whilst stationary and held it at about 4k revvs to get it to pass the emissions test. After 5-10 minutes the car overheated.

First off all, steam came out the bonnet then I turned the engine off but then even more steam came out and the temperature gauge shot up.
When I moved the car, there was a big puddle underneath and most the coolant had drained out.

Today I've topped the coolant up and jacked the car up. I got it hot in the same way as the yesterday but there's no leak and it's not having any overheating problems.
I can tell that when it did leak it was the same side as the coolant tank as the foam strip on the undercover has only absorbed coolant on that side.

Any ideas what could have caused this?

I have replaced my coolant tank cap because someone over at rx8ownersclub.co.uk suggested this. I'm just looking for any other ideas or someone who may have experienced this problem in the past?

Well, if you don't have a persistent leak then it very well have simply been the cap. It could also have been the cap doing its job; that of releasing excess pressure when the cooling system reaches a particular threshold (13 PSI IIRC). Any temporary blockage from the radiator, thermostat or water pump could've caused that.

You might check to see if the cooling fans work. These cars do not cool well when sitiing still, even when the fans work.

Hope the overheating episode didn't damage anything.

Ken

Thanks guys.

I too hope nothing got damaged. I did turn off at the first sign off steam. It failed on emissions so I got to fit a new cat. They shouldn't need to rev as much next time so it should hopefully be ok.

The fans seem to work, they stayed on after I turned the engine off.

why was it revved at 4000rpm for 5-10mins straight? this is not good for any car standing still.

To try to get through the emissions. I won't let them so it again plus there should be no need once the new cat is on.

check your radiator... check the nipple on the top of the the radiator for any signs of cracks or leaking coolant, you should see this when the car is hot,,, dont burn your self...

I bet it was the cap. There was coolant everywhere in the engine bay right?

The extended 4k rpm with no stationary fan helping cool the radiator could have simply done it. By the time the fans come on, the waterpump and thermostat can't do anything as the majority of the coolant in the system has already be circulated and heated too much.

You can try and check your radiator cap for damage/cracking to the rubber seal but it was most likely the stationary revving that did it...

I think it must have been. I swapped the cap with a spare but there didn't appear to be any damage to it.

I have driven the car for over 70 miles with lots of beeps and it has been fine and the coolant level has not dropped.

Thanks for the help.

The car also passed it's MOT after I fitted a new CAT and there was no need for lots of revving :)

You didn't post what year your car is.
Even though it pasted MOT, you still may have a problem. Check the lower radiator hose to see if it will collapse when the engine is up to temperature. The hoses deteriorate, from the inside, with age. Another possibility is the thermostat isn't opening fully.
Overheating is a problem in a rotary engine. You can loose a coolant seal and get coolant into the rotor chamber. In small enough amounts you will notice a white smoke coming out the exhaust and after a short time, your coolant level will drop. You may also notice a slight engine stumble when you start up, after setting over night. This will last for a minute or two. This is due to coolant collecting on the rotor that will get burned off or thrown out the exhaust.

I pretty sure it's all fine with no leaks at least. Thermostat works fine now.

Did you read the part where I said

'I have driven the car for over 70 miles with lots of beeps and it has been fine and the coolant level has not dropped.'

Al

The note you posted at the end of your response is exactly what is taking place with my car. I have evidently blown a coolant seal as I am getting that heavy white smoke when the car first starts, plus I am getting that rough start that last nearly a minute before the car calms down. For this particular issue, what is the fix? I have been told the car requires a new engine, which made me place the vehicle in long term storage (the mechanic was speaking of a 5k dollar fix). Any feed back you can provide will be appreciated.

I replied to your PM with information specific to you.
For everyone else. I know of no fix other than rebuilding or replacing the engine.

In the future, please start your own thread. Jumping in on someone else confuses the issues and your problem, while similar, may require a completely different solution.

I don't get white smoke or a rough idle. I don't think my problem wasn't a seal. When it leaked, it gushed and steamed out the coolant bottle (or at least that area). Now, without prolonged stationary revving, it's performing perfect over 70 miles of beeps.