I have a 2004 ford mustang 3.9l with 171k miles and it has been overheating only when the ac is running, the ac compressor was replaced back in Feb, so I do think that is the issue, I'm thinking it is the radiator, because I tried to do a coolant flush but was only able to get about two gallons when the car take almost three gallons.
Also it has a hissing noise coming from the rear of the car when on, is that an EVAP leak making that noise or something else? No check engine light currently, bud did have one back in Jan for small EVAP leak, checked fuel cap and cleared it, had not came back on. Just want a second opinion on possible causes.
You might try a new radiator cap first before going to the expense of a new radiator. Next, check for a stuck thermostat and if bad, get a fail safe one.
Already did radiator cap, then I did thermostat, then I did flush, so I already crossed those off the list
Yeah if nothing else is wrong I'd replace the radiator if it only overheats when you turn the AC on cuz that adds extra heat in front of the radiator from the condenser that's where the hissing do my video finding engine vacuum leaks with a cigar
Would the cigar trick reach all the way to the back of the car where the hissing is coming from?
@Xrayto Scotty does not answer follow up questions in this thread. Also, the cigar trick Scotty mentions is for the front to find vacuum leaks - doesn’t reach the back. You can do it separately for the back (I.e. for the EVAP system) to find leak there, however. Usually you will get a P04xx code thrown if there is a leak back there.
But does the hissing at the rear indicate an EVAP leak?
Also make sure you properly burped the air out of the system. It can cause overheating when there are air pockets.
You have to make sure you get the right amount of coolant in the radiator and burp the system correctly. Two gallons is not enough coolant.
