SilverGLE

iTrader: (3)

Alright, I have a base 04 with the usual exhaust mods, HFCs and a catback. No tune, no other power mods. When I first purchased it there was an air bubble in the coolant system that I purged fairly easily.

Now, ever since I've owned the car the overflow reservoir has pushed a bit of coolant outside itself at every AX event (40-60 seconds of hard 1st/2nd gear driving, then 5+ min to cool down after a run for 4-6 runs total. I called a reputable Z shop and was told this was normal... Not so sure about that one!

First solution I tried was to replace the overflow cap, as it was obvious that's where the fluid was leaving the reservoir. Still blew past the new (OEM) cap.

I then tried to replace the reservoir with an aftermarket metal one that has about half the capacity of the OEM one. Still no go. It has a breather port around the gasketed cap.

What happened with the new reservoir is that after my runs, it would seep more coolant than normal. Fast forward, and me and another guy took turns doing fun runs, so we had 6 back-to-back 55-60 second runs. We parked it afterwards and I popped the hood in time to see the coolant seep, then start to spray from around the reservoir cap (this was after the car was turned off). It cooled down and all was fine for the drive home, no coolant smell or anything. Mind you, the temp gauge never noticeably moved beyond its normal spot below halfway.

Fast forward to today, and I'm out driving, and notice a definite coolant smell after 20 min on the interstate. Pop the hood and there's a bit of coolant around the reservoir and it clearly sprayed a bit on top of the engine. Yay. Still the temp gauge is in the same spot!

At this point, I'm not sure what my next steps to to troubleshoot are. I'm considering replacing the radiator cap with a new OEM one, replacing the thermostat with fresh coolant, and possibly having the whole system pressure-tested. I've touched both upper and lower radiator hoses to confirm they're hot, I ran the "hidden" test mode and confirmed both rad fans work on both speeds.

Cliffs: Car sprays coolant from the overflow after driving. Temp gauge registers normal. Rad fans seem to work. Tried new OEM overflow cap and new aftermarket metal overflow reservoir. Thermostat? Radiator Cap? Clogged radiator?

I haven't taken an OBD2 dongle and looked at the actual temp the ECU is seeing, but that's the next step!

eZg

iTrader: (5)

If the aftermarket overflow res is too small won't the rad suck in air as it cools? As the car heats up the coolant kind expands and perhaps 'Overflows' but then the coolant contracts as it cools. If it expands more than your new res can hold it may suck in air.

AT least a thought....

SilverGLE

iTrader: (3)

Yeah, I thought about that... It's a Mishimoto reservoir that probably has about half the overall capacity as the OEM reservoir. Filling the Mishimoto about 3/4 full results in the same amount of coolant as up to the MAX line in the OEM reservoir.

I'm going to pick up another OEM rad cap, and reinstall the OEM overflow reservoir as those are the simplest things to check. I'm also going to more exactly monitor my water temp via OBD2 and see where that is. If I can't figure this out after the next event, then I'll drain the coolant system, check the rad, and replace the tstat.

dcains

iTrader: (15)

Buy one of those kits to check for combustion gases in the coolant.

SilverGLE

iTrader: (3)

I did, test doesn't show any combustion gases in the coolant.

I've swapped the radiator cap for a new OEM piece and reinstalled the OEM overflow reservoir, so we'll see at the next AX next weekend. If it still overflows, I'll have compression and leakdown tests done.

eZg

iTrader: (5)

Even after all that .....still may just be more air in the system.

Glad it doesn't sound like head gasket.

SilverGLE

iTrader: (3)

Yeah, I suspect it's a deep-seated bubble that just now appeared. Debating if I just want to burp it, again, or do some more preventative maintenance to ensure things are 100%.