Toyota 4A-GE Cooling issues
Discussion
Just one to bounce around here.
A couple of weeks ago on the final session of a track day I noticed the engine overheating. On returning to the paddocks, we noticed the expansion bottle was full and little coolant in the system. We refilled and bled the system and drove 4.5 hours home. The car never overheated or showed signs of leakage for the duration of the trip. Following morning checked levels and found it to be a little low. Refilled and bled. after every run, I am now checking levels and every so often having to top up and bleed the system. Yesterday the expansion bottle filled so much, it let coolant out the overflow. It appears coolant is getting into the expansion bottle but not back into the system. I have obviously checked hosesvalves for blockages and none were found.
Now first thing that comes to is Head Gasket... after doing both hot and cold compression tests all appears fine there.
The other thing is a leak in the system, but no signs of leaks found...
Anyone had any similar experiences with a 4A-GE engine?
Cheers
A couple of weeks ago on the final session of a track day I noticed the engine overheating. On returning to the paddocks, we noticed the expansion bottle was full and little coolant in the system. We refilled and bled the system and drove 4.5 hours home. The car never overheated or showed signs of leakage for the duration of the trip. Following morning checked levels and found it to be a little low. Refilled and bled. after every run, I am now checking levels and every so often having to top up and bleed the system. Yesterday the expansion bottle filled so much, it let coolant out the overflow. It appears coolant is getting into the expansion bottle but not back into the system. I have obviously checked hosesvalves for blockages and none were found.
Now first thing that comes to is Head Gasket... after doing both hot and cold compression tests all appears fine there.
The other thing is a leak in the system, but no signs of leaks found...
Anyone had any similar experiences with a 4A-GE engine?
Cheers
Thanks for the replies people 
The engine is still in a MKI MR2.
After many bleeding sessions and much head-scratching, I found a faulty filler cap (rad cap in other cars). The main seal was fine, but the secondry seal (that would be used to draw coolant back into the system from the expansion bottle) had "warped" probably due to higher pressures sustained on track.
Even after replacing the cap, the car was still overheating from time to time, but I found this was due to not bleeding the system properly and having a couple of air pockets in the system.
The loss of coolant was down to the faulty filler/rad cap dumping coolant into the expantion tank, but not being able to draw it back into the system. The expansion tank would obviously dump excess coolant under pressure.
I gave the car a full flush and renew of coolant this weekend, so fingers crossed it will be OK now.
The thermostat, oil cooler and heater matrix have also been under speculation, so will monitor things closely and replace as neccessary...
The engine is still in a MKI MR2.
After many bleeding sessions and much head-scratching, I found a faulty filler cap (rad cap in other cars). The main seal was fine, but the secondry seal (that would be used to draw coolant back into the system from the expansion bottle) had "warped" probably due to higher pressures sustained on track.
Even after replacing the cap, the car was still overheating from time to time, but I found this was due to not bleeding the system properly and having a couple of air pockets in the system.
The loss of coolant was down to the faulty filler/rad cap dumping coolant into the expantion tank, but not being able to draw it back into the system. The expansion tank would obviously dump excess coolant under pressure.
I gave the car a full flush and renew of coolant this weekend, so fingers crossed it will be OK now.
The thermostat, oil cooler and heater matrix have also been under speculation, so will monitor things closely and replace as neccessary...
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