Chicken12

I am looking for some advice. I live in the San francisco Bay Area and we drove up to south Lake Tahoe via highway 50. Everything seemed to be going well until we were about 10 miles outside of the summit. I have a 99 4Runner sr5 with the v6 engine. It normally runs exactly in the middle of the temperature gauge. As we were going up the summit it started to rise about 1/8 higher towards red but was still far from red. I then noticed a little steam coming from the front left of the hood so I pulled over. The steam was coming from the top off reservoir so I carefully pulled the cap off all the way and there was not a ton of water in there but what there was seemed like it was boiling. I proceeded to dump a few water bottles worth of water in there and cranked the heater to max and took it easy into town.

After reading these forums last night it almost sounded like it might be the fan clutch going out on the car. So this morning before the car got hot I checked the water level on it. The resivour was bone dry so I popped the radiator cap and started filling it up. The radiatior took about a little less than a quart of water and then I filled up the resivour to the line. I proceed to drive around town until the engine came up to temp and I took a rolled up magazine and gently tried to slow the fan. At first it did nothing so I tired a little harder and have about 10 seconds I was able to stop it. So figuring that was the problem I wanted to see how the 4Runner was doing so we did a 10 mile drive. This time with the raditior and resivour topped off the temp never even made it up to half way. Thinking we would be good enough to make it home tomorrow I turned around to our hotel but stopped for a quick lunch on the way back. Before we left lunch for the hotel I figured I would check the coolant level again and it was low again just like yesterday.

So at this point I am confused. I think the fan clutch is going but not sure if I have another problem or not due to the coolant dropping so fast. Today's drive was about 20 miles round trip so not sure what to think. We are hoping to leave for home tomorrow around lunch time but not sure if it is safe or not to drive the nearly 3 hour trip. The local Toyota dealer does not have a replacement fan clutch but o'reilieys did. I just read here that everyone said they were junk through. If I stop every 30-40 minutes and make sure the resivour is full and watch the temperature gauge do you guys think it would be safe to make it home? Thanks!

Chicken12

One other thing, I checked the ttransmission fluid and its a nice clean red so I don't have any issue yet on the raditior leaking into that. One other bit of detail. Mother 4Runner has about 225k miles on it and I last had the timing belt and water pump done at about 125k so it's getting up there in age. Thanks again!

millball

Sounds like you are loosing coolant somewhere, whether you have an external leak, or you have a headgasket problem, some diagnosis will be required.

When cruising at highway speeds, the fan has little bearing on how hot the engine runs, because of the great volume of air forced thru the radiator by the trucks forward motion.

It may be that your fan clutch is bad, IDK, but you only need the fan to pull air in during relatively slow speed operation, and stop and go conditions. Look elsewhere for the solution to overheating at speed.

If you watch the temp gauge, and it does'nt loose coolant too fast, you may make it home. I'd try hard to find and repair the leak, if at all possible, before starting out. Good luck!!

Chicken12

It's was late when I posted this last night and forgot to include one other thing. It seems like the coolant leak is via the coolant boiling over from the reservoir. When I got back from the little test trip now yesterday I noticed the fender well of the front driver side wheel was soaked and some even ran down to the running board under the drivers door. I did some additional searches here last night and it sounds like that could mean the radiator cap is going. Does that make sense? I looked around as much as I could and that's the only place I saw where the coolant was coming from.

The 4Runner has been running great till this trip. One difference is this is the first time in a long time we have been at high altitude. We live at just above sea level and the summit here is nearly 7400 foot. Thanks again!

J2F42C

Head gasket. The bubbles in the coolant in the reservoir are a giveaway.

Rent a pressure testing tool from an auto parts store, hook it up, pump up the pressure to 15 psi and if it drops any within 15 minutes or so, then you have an internal coolant leak somewhere, most likely the head gasket.

If it doesn't drop then check the thermostat to make sure it is opening up.

habanero

Had the exact same symptoms in the 96- turned out to simply be the radiator cap. Replaced the cap with something from Auto Zone because that's what was open. A year later it happened again- radiator cap again. Both situations occured at higher altitude than our usual- we're normally 500' above sea level. One Toyota rad cap later and it's all good for the 96.
But...
Have also had those same symptoms in another car-though elevation was at the usual 500-700'- that one was a head gasket.

What's the oil look like?

Chicken12

I figured I may as well give the radiator cap a try. Stopped at o'riles on the way out of Lake Tahoe and bought a new one and a few jugs of coolant. I also doubled checked the oil and it looked clean. I then went to replace the radiator cap and when I pulled it off this time it fell apart in 3 pieces. This is like the 4th time I have taken it off since this started. I put the new on and we are now half way home and the coolant level has not moved. Thanks for the help. I'll post more details later

stevegriffin

I think that is really your radiator cap. I already experience overheating on my truck and replaced so many parts like water pump, radiator fan, gaskets worst that happened to me is when i forgot to close my radiator cap which lead to overhaul of my engine because of my dumbness. Radiator was empty with water because of it. haha oh well lesson learned.