Hi Guys,
Have an 88 4Runner 3.0 that only starts to over heat when the A/C is on. Tried new radiator, new water pump, new t-stat, new hoses and belts. What am I missing?
Thanks.

 

First post in 8 years?

Anyway, I would suspect the fan clutch. The fan should have some resistance when cool, and more resistance when hot. I can easily hear my fan sucking air when I have my AC on.

 

I would check out the fan clutch before any thing else. However you may have a issue with the compressor or the AC belt being way to tight.

 

I would hook up a set of a/c gauges and see what your high side pressure is, you may have a restriction in your condenser.
I also agree with rustypigeon and cbr600rx7; you need a good functioning fan clutch.

Are you overheating at highway speeds or sitting idle?

 

Has it been 8 years! There is so much info on here this is the first time I couldn't find my answer. Thanks for responses! Guess I should have mentioned that I have a Black Magic Electric fan on my radiator that I have had for years with no problems. I recently had my A/C checked and the pressures were right on. Speed doesn't seem to affect it, it's happened at around town & highway speeds randomly. Temp drops quickly when I turn off the air and returns to normal. I'll check my belt tension in the morning. I've owned this 4Runner since new and finally decided it was time for a complete rebuild, looking forward to posting more often.
Thanks Everyone!

 

I am guessing here if it is not your fan clutch I would think maybe a external blockage of the cooling area

Then the interior of the radiator is now blocked enough the extra added heat from the condenser is just to much for the cooling system to handle .

Myself I have had nothing but problems with electric fans !!

Is the electric fan motor getting old and tired ??

Something causing the input voltage to the fan to drop reducing the rpm ??

It most likely be one of these issues

 

Thanks for the reply! I've been thinking about the voltage drop. Been chasing electrical gremlins lately, thinking i have a bad ground somewhere. Going to start by changing the big 3 wires with a larger gauge and work from there. Checked for obstructions everything is clear.

 

Finding the root cause will take some troubleshooting but I can tell you straight away that you are not pulling enough air through the radiator to compensate for the heat radiating from your condenser. I have a very simple test for this on my semi trucks at work. I just engage the fan clutch and then hold a shop rag up to the front of the radiator. If the air flow will hold the rag against the radiator on it's own then the fan and radiator pass the test. If it falls to the ground then I start troubleshooting. That's not going to help you but may give you an idea for your own test. I can tell you that the earliest symptom of a fan clutch failure is high coolant temp with AC on and normal range with it off. I think you can rule out the AC system as the problem and check out the stuff Wyoming9 posted above. I have never used an electric fan on a Toyota so I won't be much help. My stock fan (89 4Runner) moves a ton of air. So much so that the noise of it irritates me. It would be hard for me to imagine a 12V electric fan being able to pull like the belt driven ones. Check your wiring. A loose connection or weak ground will really slow that baby down.

Oh, and one more thing. I doubt you are using the original fan shroud with the electric fan but the shroud is very important when it comes to pulling air through the radiator.. If you have removed any part of it and still have it, reinstall it if you can.

 

I have yet to see one of these Toyota`s with the fan shroud still attached

I could see in temperatures over 100 F where it would make a difference

 

Believe it or not, mine's still on there but I can see why folks take them off. They sure do get in the way. I'm sure you're right about it not making much of a difference. It seems like more of a safety feature than an aerodynamic device. Most of my experience with cooling packages is on big trucks and heavy equipment where fan shrouds are a big deal. On the big trucks, you really notice it at around 88 degrees and idling for extended periods. The fans will run almost continually which robs HP and fuel economy. They will also lock up an AC compressor or two or three without the shroud installed. Don't ask me how I know. I just went out and looked at mine again and you're right. That thing isn't going to make a big difference.

 

Thanks Everyone for the ideas! Charchee just tried out your shop rag idea, works like a charm! Held shop rag in front of the grill and it was sucked into the grill and stayed. Flow is not the problem. The fan I'm using is from flex-o-lite made for our trucks. It's a one piece unit with the shroud that bolts right on and flows 3000cfm. While I was checking things over I discovered the ground wire was loose in the connector that attaches to the fender. Crimped on a new connector and reinstalled it. Hopefully this will fix my intermittent problem I've been having. A bad ground would explain why it was happening randomly at low and highway speeds. Thanks for all the Help! I will check it out over the next couple of days and hopefully can move on to the next part of the project.

 

How are things holding up now?

 

Hate to be the guy to say this, but when I was running an e-fan I was always near the ragged edge of not enough cooling power. Hot summer with the AC on always equalled temp overshoots. The stock fan, with a working clutch, and the shroud of course, just provides way more cooling.

 

So far so good! But this week hasn't been really hot yet so we'll see. Fixing the ground did help fix some of my other small issues.

 

There is a product that I break down and buy from time to time from my local radiator / ac shop they call coil cleaner. Don't know the brand but it's expensive. We only use it when we are cleaning a radiator, evap, etc that we have no way to get washing water to. I wouldn't have believed it the first time the shop recommended it but after I watched them spray it on a new looking radiator I bought a couple cans for my logging jobs. A ton of crud just came running out of it from I couldn't tell you where and you didn't even have to rinse it. It foams up and they told me breaks up deposits that are packed in so deep you can't see them. I normally use BBQ grill cleaner on mine at home and then use no pressure hose water to rinse it out. Works well for me but what I'm saying is the cleaner those cores are, the better they will cool. Never use a power washer. We bought a big new washer for the company about two years ago and had 4 AC system failures in one week after my drivers flattened the fins on their condensers the first time they tried to clean out their radiators.

That's not going to make your problem go away but double check that your fins are clean all the way through. Crud can build up right in the middle where you can't see it from either side. I think that is what that coil cleaner product is helpful with. If you don't have another option for air flow, keeping it super clean may be your only feasible option to get you through the summer.

 

Thanks, I'll check it out.