Epic Ed

I've had more issues with my damn '95 4Runner over heating the past couple of years than I care to mention. Part of that is simply a fact of living and driving in the scalding temps of an Arizona summer. Well, summer has arrived a little early with temps in the 105-110 range all week, and that first heat wave always exposes the weaknesses in the cooling system that were lurking during the cooler months.

Over the past year due to various cooling issues I have had my radiator re-cored and now am running a three row radiator. No maintenance has been done to it since the install May '04, but I haven't had any coolant loss, either. I had the water pump and thermostat replaced when I had a new engine swapped in last May. Had some fan clutch issues last March and installed a heavy-duty fan clutch. Electric fan that cools the AC compressors was also replaced at that time. New hoses (upper and lower) were also replaced during that same time frame, so every freakin thing I can think of of the POS is nearly brand new.

Mix in the TJM T15 bumper shortly after all of this was done and the engine was replaced, and there are two Hella 500 series lights mounted in the usual position. I ran all summer long with frequent weekend trips up to Flagstaff that involved long, hard, uphill pulls without incident. Fast forward to last weekend...

My mechanic is also a good friend of mine. He, too, owns a second gen 4Runner and is very familiar with their quirks and follies. I trust his work and his judgement, but this time I'm a little skeptical. I had some bizarre over heating problems as follows:

- Runs fine at idle 100% of the time.
- After a short drive with the AC on the temp gauge starts to climb after about 5 minutes. This happens intermittently about 80% of the time.
- When temp starts to climb, if I leave everything alone (AC on), the temp gauge drops back to normal most of the time after peaking mid-way to the red zone on the temp gauge.
- If I turned the AC off when the temp gauge starts to climb, the temp drops back to normal immediately.
- I have good AC flowing as long as the temp gauge is running normal.
- Trouble shooting while parked reveals the AC fan is not moving when it is over heating with the AC on. (possibly bad AC fan?)


- Take the AC out of the equation -- I drove up to Sedona with the AC off and had no problems with over heating on the way up. On the way back, after climbing the long steep hill out of Camp Verde, my "AT Oil Hot" light went on.
- I have an AT cooler and have never had any transmission over heating issues and that's a climb I do every weekend during the summer. I had to pull over and let it cool down five times on the remainder of the drive home.
- When I got close to town I got caught in a 4 mile traffic jam and with the AC off the temp gauge started to climb and didn't back off as it headed for the red. I had to cut the engine to keep it from pegging out in the red and causing the usual catastrophic damage we've all come to love when our head gasket blows.
- After 20 minutes I did a U-ey and went back the other direction to get some air flow going through the engine and it immediately began to cool down.

Here's the kicker. My mechanic thinks this is all due to the lack of air flow and obstruction due to the T15 bumper. I think I have multiple fan-related issues going on, with the situation being exascerbated by the reduced air flow.

My questions -- any of you who run with the T15 bumper ever have any problems with over heating? Any at all? Any modifications you've had to make to increase air flow?

Secondly, given the symptoms above, what do you think is behind my over heating issues?

Thanks for your help.

Ed

KING

You and I are running the same issues, with the same engines, and roughly the same year, minus one variable: the TJM.

I am in the process of replacing the thermostat for fear that it may not be functioning as it should.

The radiator has been taken apart, cleaned and filled with new coolant.

I need to double check the fan, as I too seem to be having a variety of fan related issues.

The one that tickles me the most is when doing highway speed, with below than normal engine temperature, the engine fan kicks in.

As I am reading your post, I am just thinking, you and I need to have a one to one talk and nail this down or call it for good.

I will be doing a trip to Colorado in June and I am now skeptical how the performance of my truck will be and if it is capable enough to make it there and back without any issues.

Epic Ed

Yeah, the unreliability issues have been killing me. There's nothing that shuts you down quicker or makes you hesitant about the stability of your truck than temperature issues.

Did yours start with the recent heat wave, too?

Dude -- you're just down the road from me. We oughta go wheeling when we get this mess sorted out.

I ran into Christian (96 Runner) a couple of weeks ago at Starbucks -- good guy. Maybe we can get a group run together.

Ed

Ironmike4x4

The mechanic you talked to can be right about the restriction in airflow. At GM, it's not recommended that you put anything on the front of the grill for reduced airflow. One thing that could be the problem. Did you ever take any airdams or anything like that off? At idle the airdams created a vacuum swirl helping the cooling fans to be more efficient. You would be surprised at how much of a difference that has made on the Camaros and lowrider cars where I work. People hate how it scrapes the road then take them off causing their problems.

Epic Ed

Nope. No air dams removed. I can agree that it may be contributing to the problem, but there's got to be more to it than that. Just found out he fabbed up a piece of sheet metal to block the lower opening at the bumper. This will cause a more "forced air" flow up to the radiator. We'll see...

Ironmike4x4

Sorry man, I wished I could help more. That's all I could think of on the top of my head other than the fan isnt turning on, but that would be the first I would check. If you were local then I could probably diagnose it. What is the CFM rating on the fan or do you know?

rimpainter.com

This is highly unlikely, but is there a chance that the temp gauge itself is faulty?

Sorry to hear this Ed, I know car problems suck. I bet a 3rd gen is looking better and better each day!

I am not sure if a 3rd gen fan would fit on a 2nd gen, but I have 2 spares and you are welcome to give one a shot if you want.

Epic Ed

Thanks for the input, guys.

Ironmike -- no, not sure what CFM is. How would I check what the fan is supposed to produce vs. what it currently produces?

As for the temp gauge, not likely. Most of the time it hasn't gotten hot enough to boil, but it definitely did a couple of times. Weird. These intermittent problems are a whore to fix. Also not sure about the 3rd gen fan, but I'll check. It may be a solution. I'm also considering going with the electric fan mod at this point.

Ed

Yota4runner

Air in the cooling system? Seems to simple to be it. I remember when I had my Grand Prix, it did the same thing...in the middle of winter, I pressure tested the Cooling system and found it had a small leak in it. put some stop leak in it and it fixed it right up. Obviously not a long term fix but I drove that thing into the ground anyway.

ChickenLover

I had my very first overheating issue today, it was similar to what you described (and I have a flexalite blackmagic electric fan). This is what I plan on doing and I recomend the same to you. First I'm going to replace the t-stat (OEM of course), then burp the system. Your t-stat is only a year old, but they can go at any time. Then I'm going to take a closer look at my EGR. Right now it is plumbed half-assed into my intake (it's hose is just sitting in the bottom of my airbox). The EGR's purpose is to help the engine run cool.

Epic Ed

Hmmm...interesting. I wasn't aware that the ERG played a part in cooling. Anyone else confirm this? The reason I'm interested is because mine is no longer part of the engine. I'm aware of the exhaust implications, but had no idea about the cooling aspect. You might be on to something. So yours is happening even with the flexalite, huh? Dang -- that's discouraging. Let me know what resolves the problem. I'll definitely have him check for an air pocket if he hasn't already.

Ed

dragon564

The removal of the EGR can chage the amount of fuel used in the air fuel mix...leaner is hotter which does have a direct impact on the coolant temp. I keep seeing the fan clutch issue pop up, unless your system is completly different than mine that huge setup is not a true clutch, it is there more to provide some spin up and spin down room for the fan, not engage and disengage of the fan. If your gettin in to the red with the A/C on and the AUX A/C fan in the front is not kicking in then I would start to think the the relay controling that fan is going out or the temp sensor that controls it. You can wire it so that fan is always on or connected to an on/off switch. I highly recommend going with a all electric cooling fan set up (i.e. flexalite or the Taurus swap) for the main. If the tranny cooler is not in the air flow of the main fan or aux fan then I would also look at getting a fan just to cool it. I would need to see a picture of the front of your truck before I start jumping on airflow problems created by t15 and lights. I used to own a GTR that had been highly moded in the engine bay, I had various over temp problems until I installed an oil cooler which helped alot and after I provided a fan on the oil cooler my over temps went away, and the current owner says he has not had any temp problem unless he forgets to turn the fans on......

Epic Ed

Mighty good post, Dragon. Thanks. I get the explanation of running lean -- so it certainly could be contributing. I'm heavily leaning toward the flexalite mod. You're are supposed to pick up a few HP by doing it, too, aren't you? We have discussed an oil cooler so that may get worked into the mix, as well. Heck, I'd be willing to put five radiators and three Eskimos in there if I thought it would solve the problem.

Thanks,

Ed

rimpainter.com

I can help you with the install if you need it Ed. I recommend going dual if you can.

Have you seen the Taurus fan mod? Check that out too. It is popular with the 2nd gens.

I run electric fans and have never had a cooling issue, even while off-roading in 100+ temps.

Let me know if you want to try that 3rd gen fan also.

dragon564

Ed,

I have no DYNO run from a manual main fan to a electric main fan, however the electric set up is much lighter and the engine is not turning it so seat of my pants says a little bit more pep, and every little bit helps the 3.0. Also with the manual fan the air flow is controled by engine speed the man fan at idle has to pull the air through the grill and then push it by the engine bay at idle it just might not be able move enough air since the T15 went on. The electric always moves at the same speed and cooling can occur at idle. Also where did you put the trans cooler? Could it be adding to the blocked air flow therory?

Epic Ed

Makes sense...

Tranny cooler is mounted under the vehicle, passenger side, behind the differential and away from the exhaust pipes. A fan may be needed there, too.

Ed

bamachem

1. Sound like it could be a bad thermostat. You might want to change it out.

2. Could also be a bad fan clutch. Have you checked it???

midiwall

fwiw, I'm running a TJM T-17 (a -15 without the hoop) and a pair of Lightforce 170's in front of the grill. At the moment cooling is provided by a Flex-A-Lite setup, and when it works, it's great.

I've had a horrible problem keeping these fans running... I've been through two mechanical controllers (they love to get caked with mud, corrode, and become worthless) and just last weekend I trashed a brand new $65 electronic controller and broke two blades off of one of the fans in the pair.

I'm in the process of going back to a mechanical fan. Replacing the setup will cost me upwards of $200, and I can buy a new clutch and a Flex stainless fan for a lot less that. I used to be a HUGE proponent of the electrics, but it just hasn't worked out for me.


HP wise, yes, it will free up a couple based on there being less drag hanging off of the crankshaft. You'll also pick up some throttle response on the bottom end since you have less mass up there to get spinning.


Anyway, I don't mean to turn this into a gripe about the electrics, I just wanted to share that I have a lot of stuff blocking air flow and I run cool. I don't expect the mechanical to be any different.


Christian; I'm gonna PM you about coughing up one of your clutch assemblies.

rimpainter.com

Uh oh! What did I get myself into?

Based on what you are saying Mark. I might need to keep one around as a spare!

I am thinking about squirting silicone gel into the openings of the controller box with all the wires plugged in. That should make it water tight and still allow me to unplug the wires, should the need ever arise.

KING

Ed, the cause of my recent problems have been because of the heat wave which was Friday and Saturday.

Friday was bad, Saturday was worse.

On Friday, I got stuck in traffic jam on Grand Ave waiting for train to go by. I was there for a thirty minutes at the hottest time of the day - 5 in the evening.

I see my temperature climbing but think nothing of it since it has been doing fine for the past nine months. After a while, I look at it again, it is about 1/4 shy of the red spot. At this point, to get ouf of the jam and to cool the engine down, I make a u-turn and head home using another route. No problems after that.

Today, I left the truck idling as an experimenting feature. Time was around 2PM and the truck was left idling, with the A/C on for thirty-five minutes. The needle made it as high as the middle but then cooled back down, and so forth. I then opened the hood and it never moved from the cool spot. Grant it, it isn't any where near as hot as it was Friday or Saturday.

In addition to all these heating issues, I seem to think I do have an electronic problem, either with the gauge or the sensor.

As I have repeatedly said, when my truck has been running for a lengthy period of time and if I turn off the truck and restart it within the next twenty minutes, the needle rises past the half point mark but immediately cools down.

I have absolutely no problems during the "winter" months just like you. As soon as those temperature begin to exceed the 108F mark, my truck starts to act up.

I have had no overheating issues while off-roading in the desert in summer months.