over heating prob help!!!!

[stealthyQ]

Hey guys ,I have an overheating prob with my 94 g50 and was hoping that you guys could help.Let me start by telling you that my radiator and thermostat have both been replaced .The system was vacuum bled and pressure tested with no leaks .The system seems to hold pressure fine with no issues and could be driven for a week straight without issue,BUT,all of a sudden out of nowhere the temp gauge will rise and it will start to spew anti-freeze out of the pressure release on the upper cap.i have been a mechanic for a number of years and have never had this much trouble with a colling system ever. any help would be greatly appreciated

[Q45tech]

Reverse pressure test or read the actual running pressure, use HC tester to check coolant for combustion gases.

OEM or brand name rad? Nissan Thermostat? Aux Cooling Fan functional?

[goody90q45]

Is it happening in stop-n-go traffic (fan clutch or fan solenoid) or in steady speed traffic? Is your fan running at idle?

[elwesso]

Water pump?

[qship96]

the Pressure Relief cap should be on the radiator,the cap near the thermostat/engine should just be a cap

[carfrk666]

if all else fails, check for slight possiblity for a head gasket gone bad

[Jesda]

I suggest a leakdown test to determine HG failure, which is quite rare on the Q.

[Jeff Williams]

Sounds like the water pump might be going out. Or you have blockage in the water system.

Be sure to check the A/C Condenser for blockage, and make sure the electric fan is working in the A/C mode.

Also, make sure the gasketing around the radiator is intact. If it is missing, the car can loos a lot of airflow through the radiator.

Overheating will melt the knock sensors, and they are $1,200.00 to replace. Don't drive it hot at ALL!

[stealthyQ]

I put a sniffer in the cooling system all was well .Water pump was also replaced recently.After pulling what little hair i have left out.i think ive got it down......after all is said and done my fan clutch took a poop i replaced it with a 1600cfm hayden electric and thermostatic switch and so far so good . the clutch fan was working sparatically sometimes yes at full operating temp and sometimes no, which is why i think i overlooked it i appreciate everyones quick responses ....thats why i love this board.

[92Q45guy]

Keep an eye on your alternator now.

[stealthyQ]

Already ran a voltage meter on it and it only draws .6v and with all accessories on Heat, radio, my xm, headlights and the fan running it still never goes under 13.93v , but ill keep checking it from time to time .Thanks