Hey everyone, I'm new to the board - I have an 88 GTA with the 350 TPI motor in it, and I am totally stumped on a cooling problem. It usually stays below 220 just driving without AC, but with it on, (especially on a hot day, like in the 90s) it starts to get really hot (above 240). Once I shut the AC down, it cools back down after a bit - and goes right back up when the AC is turned back on. It gets hotter on the freeway than it does around town for some reason. My car has a 160 degree thermostat, SLP 4 into 1 headers (not coated or wrapped), the motor has been recently replaced and has @6k on it, the radiator is a stock replacement and was changed when the motor was swapped, the radiator hoses are new, the coolant is all new, my air dam is in place, the coolant temp. sensor was recently replaced, both fans and relays are working - I'm out of ideas. I don't want to just start replacing stuff right and left, because I don't have that kind of money - not to mention I'm out of stuff to replace.

In another post, I noticed someone had said that their car overheated when their ignition module went bad - I was wondering if this could be the problem, cause sometimes (rarely - it's happened twice that I can remember) when I'm on the expressway and I floor the gas to go around someone, the car will get a noticeable increase in power and throw a code 43. Could my ignition module (or ECM, for that matter) be taking a crap on me and making my car run too lean (and too hot)? I don't know a whole lot about this, my knowledge on the subject is fairly limited. I tried to include everything I thought could be related to the overheating. Sorry for the long post, but any help is very much appreciated! TIA

 

Well, my first thought was to check the fans but you say they're working fine. The problem seems to have something to do with the AC, so concentrate on that system. Could the clutch be bad making it hard for the engine to turn? Could the system pressure be incorrect?

 

I think the system pressure is OK - although I'm not sure. The AC has been professionally retrofitted to R134a by a reputable shop at the same time the motor was replaced. How would I be able to check system pressure, or if the AC clutch is bad?

 

A/C clutch shouldn't have anything to do with your problem. The clutch should be released when a/c is off. With the engine idling and a/c shut off, the center of the clutch should not turn. When the a/c is turned on, the center section should lock up and turn without slipping. If the clutch is slipping, (very rare) you should hear it making noise. Make sure that the radiator fins and the area between the radiator and condenser is clean. Leaves or debris in the space between the condenser and radiator will cause overheating.

 

I am a Nissan tech by day and I had a weird one last week. I had a 1996 Maxima overheating only with a/c on. It got so hot it melted the plastic fans right of their motors! I saw the a blown fusible link to fans and thought that was the problem. Nope, the melted fans bound the motor and popped fuse. But the fans where not the original problem. I had technician next to me hold a cigarette in front of the grille and try to notice if smoke/air was being sucked into the grille area. It wasn't. We compared it to another car and the smoke was drawn right in on other vehicle. I removed the refrigerant from the system. Removed the condenser. You couldn't even see through the condenser. It was packed full of dirt and road grime. I took condenser to the carwash, powerwashed it, and installed it. Charged system. test drove. Bingo! Car was fixed. I would check restrictions in front of the grille, condenser, and air dam area.

Good luck,
Hank O.

 

Couple of questions. If you are running a colder stat and driving 45 or so where is your average temp. It should be below the first line on the guage, if your average temp is around 220 with that kind of driving and a 160 stat you have a problem. First thing to check is base timing. Make sure it is set when engine is hot with the set timing connector disconnected. I think most are 6 deg BTDC but the VECI label will tell you for sure. Me thinks your average temp to start is too high and running the AC is only making the problem more apparent. I have a zz-4 block and all stock emission controls. New OE radiator and 195 stat. In normal driving it runs the same as most TG's it stays right on the first line between 100 and the 220 points. In traffic it hit a little over the 220 mark then the primary fan kicks in, and it will stay a little below 220 until I start moving and the airdam kicks in. Question, were the fan motors ever replaced. Make sure the fan is pulling air in, not pushing towards the rad. Keep us posted

 

I would definetly check to see if your condensor is not full of crap and in good condition. Next i would let the car warm up with the a/c on, and pop the hood and see what if any fan(s) come on.

When the a/c is turned on and you are going faster than 35mph i believe, then non of the fans should come on, and the car relies on the airflow to cool it down(unless the temp is where the fan normally come on at). But when sitting in traffic there is no air flow, so the car relies on the fans to keep it cool. I would check to see what your fans do when the a/c is on, sitting idle in park, and notice what temps the fan or fans come on at, if they come on at all.

 

OK, I had a chance to check the condenser and radiator - there are no blockages in either one. In fact, the radiator was replaced with a brand new one about 6,000 miles ago - so that should be OK. As far as I know, the fan motors were never replaced, but both fans are working, and they do push air toward the motor. In normal driving without A/C, the temp usually stays about 2 marks before 220. On really hot days, it'll climb to just shy of 220 without A/C. I haven't checked my timing yet. Thanks for all the help so far everyone, I'll let you know if I ever get this taken care of.