Mysterious coolant leak on the M3, any ideas???

[ThirdgenTa]

Is it possible for around a gallon of coolant to spray out of hte cap?

Yup, happened to me a few months back in the city. Here I am cruisin at like 70mph and I look down and my temp gauge is pegged. Pull over at some ghetto gas station and picked up some coolant and bottles of water. Must have lost a few gallons at least. And at least my cap fell in the engine compartment and actually hung on for the ride.

 

[Turk]

The more I think about it the more I think it was a loose cap. Thanks for the replies guys, and thanks for scaring me 10 sac!

 

[Bob Kazamakis]

Only one way to find out. Go rip around for a few hours and see what happens!

 

[Stink Star]

Could Definetly be a compression leak into a coolant jacket. It over pressurized the system and made the cap blow off. Rip on the car awhile and if it does it again look forward to new head gaskets

 

[Turk]

Getting it checked after work today.

 

[willizm]

I kinda felt sick seeing the title of this thread. To nice of a car to have it spitting coolant all over. Hopefully the cap is it, but what about a faulty water pump? I believe those are belt driven and not electric on the m3's, right?

 

[Caddy_V]

I bet it was a hose. I bet there is a hole under a hose clamp that only leeks when you pull on the hose in question. This is common...

 

[Bob Kazamakis]

I bet it was a hose. I bet there is a hole under a hose clamp that only leeks when you pull on the hose in question. This is common...

A hole under a hose clamp and only leaks when you pull on the hose would be able to spew over a gallon at once?

 

[Caddy_V]

A hole under a hose clamp and only leaks when you pull on the hose would be able to spew over a gallon at once?

16 lbs of pressure times a water pump running at 5000rpm or more, i wouldn't count it out.

 

[Stink Star]

MY CORVETTE DID THE SAME THIS AS THIS WHEN I WOULD BEAT ON IT. THE HEAD GASKET WOULD LEAK COMBUSTION GASSES INTO THE COOLING SYSTEM AND CAUSE IT TO SPEW COOLANT. BUT ONLY IF I WAS BEATING ON IT.

 

[10sec]

It's a very common failure on boosted cars.

 

[Turk]

Would gas still leak in there at idle so I can test it?

 

[Stink Star]

what we do to test that failure is test the coolant for combustion materials. basically we take a small sample of coolant and add a chemical to it that changes colors if hydrocarbons are present

 

[SleeperLS]

Did the coolant spray vertical at all or just sideways mostly? All are viable options IMO. I wouldnt think coolant would spray straigt up if the cap was still on and it is indeed a screw on. Coolant test for combustion byproducts is very easy and takes no effort or a lot of time really. Do it.

 

[10sec]

Would gas still leak in there at idle so I can test it?

Doubt it, but hey, anything is possible. My advice is to just keep assuming it was a loose cap and hope she's ok. However, this could potentially be your lesson for boosting a perfectly good motor!

j/k j/k or am i?

 

[jason05gt]

Rick, could you pinpoint an area of the leak? I'd check the coolant overflow for leaks as they are typically made of cheap plastic.

Shaun has a cooling system tester when you can pressurize the system and look for leaks.

 

[Turbocharged400sbc]

haHA

being that it sat for a while the Tstat might have stuck and the cap vented but yeah youll want to pressure test it...i know i still have my eruo-pee-on closed system test adaptor for the thread on caps on those fuckers, prob in the bottom of my toolbox...im pretty sure the autozone type testers dont include the newer thread on adaptors...i might be wrong.
you can get the HC testers that test the coolant or the one's that you "sniff" the air in the system with hell even HF sells the vapor type setups iirc

 

[Turk]

The mechanic I'm going to has all these gadgets.

 

[10sec]

 

[Turbocharged400sbc]

yet it hasn't lost any additional coolant? did you overfill it/top off the res after storage? did it puke on its first heat cycle/drive?

when it puked where you flogging the skinny pedal at the point you think would have lifted the head? if so take it to him, if not it may be nothing huge just a Tstat that might have stuck closed

 

[10sec]

It's not a $300 3800, I doubt the thermostat was stuck closed...

 

[Turk]

It dumped the coolant after one full throttle run to 8400 rpm.

 

[Turk]

How bad is it lifting a head?

 

[Turbocharged400sbc]

and?

what did you pull the car cover off start it up pull out onto your street and burned rubber for 4 gears at redline, less than a minute after startup....or what?
did you top it off recently? if the res of the sealed system is too full and the system burps it will spew coolant from the lid area.
all Tstats are wax pelet type, they can and do stick all the time especially with hot running cars.

if it has not lost anything since id prob still have the guy replace the Tstat your junk is getting old

 

[C.Evans]

How much boost are you running?