94 Q45 coolant boiling over in overflow tank

[ahardb0dy]

The car has been running perfectly lately, today after leaving the car running with the A/C on for about 35-40 minutes we stopped at a store and I noticed antifreeze all over the ground, shut the car off and the coolant was boiling over in the overflow tank, started the car and it stopped, shut it back off and it started again. Temp gauge never went above half, noticed if I pressed the ambient temp button it was saying the temp was 128 never saw it read that high before, have a new radiator and coolant was at proper level, filled the radiator and drove it home with no problems.

Noticed the electric cooling fan isn't coming on even with A/C on, fan fuse under hood is good and relay next to fuses is good, found out earlier that their is a 2nd relay behind the headlight and will check that one tomorrow, checked for power at fan plug and got none.

Questions? - even if the 2nd relay is bad shouldn't I get power at the plug for the fan? Which temp sensor ( under plenum or near thermostat ) controls the fan? Anyone seen a Q do this before?

Thanks alot.

[Q45tech]

On 94 and later ecu drives the relays based on signals from coolant temp sensor and ac system.

Use a Consult to cycle fan on/off test;

Was new radiator oem from dealer, did the foam surround seal get replaced and what is the fin condition of condenser.

As new cooling means everything oem new especially every 6-7 years.

[ahardb0dy]

radiator was from carquest auto parts, it's actually metal, today the fan is working don't know what happened, both relays are good and I just got home from driving the car and it was fine. Don't know about any foam and didn't notice how the fins looked.

[maxnix]

Got to have the foam blocks for air flow management and to prevent recirculation of engine bay air.. Stock radiator is aluminum.

[ahardb0dy]

stock radiator may have been aluminum but the one that was in the car had plastic ends where the hoses attach, that's what broke on mine. Spoke to my mechanic today the electric fan is not coming on when it should he advised to look for a new fan

[maxnix]

stock radiator may have been aluminum but the one that was in the car had plastic ends where the hoses attach, that's what broke on mine.

Plastic end tanks are ATF heat exchangers. Easily by-passed with auxiliary ATF cooler.

[Q45tech]

The main point is overheats are not normal [at least until the Earth gets significantly warmer] and over heats mean some part of the system has aged and is not brand new.

Aftermarket parts may fit but not meet oem new specifications........fewer, thinner fins per square inch, less weight because aluminum is thinner, etc, etc.

Every year from brand new the reserve is reduced from component changes until with enough owner abuse the system gives up and overheats.

After all it's not like the engine can suddenly create more heat from burning the exact same amount of gasoline [same idle rpm].

Using aftermarket/used parts is usually the cause of an unsatisfactory repair.......they may be close but a -10% off here and there adds up to a boiling.

[maxnix]

And the cooling margin is very slight, so if everything is not ast least pluperfect, then a high-stress environment will result in a runaway overheating condition.