LastViceRS

My car started this less than a month ago. On the highway, it runs cool(approx. 190), but in stop and go or idling with the AC on, it will climb past 220. Car has 122,000 miles on it, motor was rebuilt about 25,000 miles ago. Coolant is full, circulating, and looks good. Fan is operating properly, and everything is in place. Oil looks good. I've owned this car for about 1-1/2 years, drove it a lot last summer with no trouble. Oh, the problem is most noticeable when temps are in the 90's - not as bad otherwise. I'm not used to diagnosing these screwy cooling systems, so what would you guys try first? Thermostat? Cap? While I'm doing this, should I go to a lower temp thermostat/fan switch? Thanks in advance for any help :hail: Brian

SpeedCat86

How much over 220 does it go? If it's only a little, then you don't really have much to worry about. The boil-over for a stock cooling system is around 255-257 degrees, and 220 is about normal for a warmed-up engine. These cars have no real air flow unless they're moving, so they tend to get hotter in heavy traffic. You stated that you run your A/C, and these 1970's vintage systems tend to put a lot of load on the engine, more so at idle. More load equals more heat. Addionally, you may want to check the space between your radiator and the A/C condenser, as this space tends to collect leaves and other debris, thereby blocking your radiator. To check this, remove the upper radiator support, and lean the radiator back to see down in to the gap behind the condenser.
Last but not least, take a good look at the ends of the tubes in your radiator. They should be nice and clean and well defined. If they look like a coral reef, your radiator is getting clogged with mineral deposits, and needs to be cleaned/replaced.

If your temperature only gets a little above 220, i wouldn't worry, that is the correct temperature, especially in heavy traffic, with the A/C on in 90 degree weather. Don't be too concerned unless the temp needle is making regular trips to the 240-250 range.
Keep us posted....

LastViceRS

OK, so I'm a little jumpy - a set of cracked heads (on another car, years ago) can make one that way. I guess I've seen it go to 240 a couple of times, and when it does, I make an effort to cool it down. What really bothers me is that it didn't act this way until recently. Last summer I noticed that if I idled the engine for a period of time, i.e., wife runs into the store and I sit in the AC, the fan would kick on at 220 and keep it there until I got the car moving. Now, the temp gauge just keeps going. BTW, I forgot to mention, I blew the AC condensor out with compressed air a couple of weeks ago, didn't make much difference. Didn't actually remove radiator support, though, maybe I'll look at that next. I haven't seen the inside of the core yet, hmm... Also, I drove it today in some rush hour traffic (infrequent for me) with the T-tops out and it still got to 220, in low 80s temps. Just doesn't seem the same. Well, I'll do some checking, thanks for your input. Brian

MG86TA

Hook up a Scanner to it and check the REAL temp, My temp guage after my rebuild less than 1000 miles ago made my temp guage run 15 degrees too hot. so my temp guage might read 220, but its really at 205 or so.. oh yah i have a 180 thermo too

LastViceRS

Well, guys thanks for calming me down, I don't think this is as serious as I thought. Since the outside temps were more tolerable, I drove it all weekend without the AC off (T-tops out), had it in town for a good hour today, and the temp never went past 210*. I'm still going to check it over thoroughly, but I'm not as worried. The motor's in good shape, and I don't want to/can't afford to mess with the internals. So, thanks for your advice :hail: and I'll let you know if and when I find anything out.