I have 240,000+ mile on my 90 4runner & in traffic with the A/C on no problem I can hillclimb with the A/C on & still no problems but the min I get to 65-70 & hold that speed it starts heating up I can turn on the rear heat & it helps alittle. I did a flush & a new 180 thermostat it runs cooler at lower speeds.
I'm prob going to get a new radiator but wanted to see if anyone had a other ideas.

 

Fan clutch?

 

fan seems fine it has no play in it.

 

on cool days & most nights it runs cool

 

I'd have the radiator professionaly cleaned. I had mine rodded and rebuilt (top end) for about $85 last year. Good as new.

 

Perhaps a bad t-stat...clogged heater lines...got any leaks? I'd say it is something other than the radiator...unless it is clogged...but you'd think a flush would clean it out.

 

I already changed the t-stat no i don't have any leaks. my heat works great lol

 

Did you ever figure out what the problem was? Mine just started doing the same thing,,,its a 93 v6

 

Not yet I am going to try to test the radiator & the hoses this week end

 

Ok, well let us know what it is,,,,I figured i would pull the radiator and have it rodded. Thats what the problem is I bet. But f just doing a flush works ,,,then I would rather go that route

 

Hey dude, dont forget to check the operation of your aux cooling fan, operated by thermo switch... sounds like the prob may be happening during a/c poeration.

 

To me it sounds like a radiator problem. At highway speeds, the "ram air" does most of the airflow through the radiator. Does your aux fan function with the A/C on? Radiator isn't packed with mud?

 

the radiator is clean ( as far as air flow) & the aux fan works

 

I had the same problem. I took the radiator to a shop close by to check the flow and they told me that it was fine. They tested it by filling it with a garden hose and if it didnt back up then it had a good flow. That made since to me at the time so I ended up pulling my tarus fan, buying a new shroud and after market fan clutch just to have the same problem.

I ended up going to another shop and the guy showed me just how bad the radiator was when he was rodding it....I ended up getting a new radiator and things have been fine ever since....

 

I installed a new radiator last night along with a Taurus fan. It idled for almost 20 mins with the air on & no problems. I hit the interstate & had no heating problems. But it was night so I will see later on today.
I was suprised to find a good bit of crap on the front of the radiator blocking airflow.

 

Ok that was it. The new Radiator fixed it. So daveyboy if yours is doing the same thing then there is a good chance its your radiator or its blocked