Biazzare Tacoma Overheating!

[toyotatifft]

The Vehicle: 1997 Tacoma 4x4, 2.7L engine (3RZ) with automatic transmission and AC.

The Problem: Slow loss of coolant. During the summer I have been experiencing overheating, but not all the time. Usually I can drive for like 40 minutes or so, then suddenly I'll notice the temp guage going up slowly from it's normal position. Sometimes it has climbed into the red zone, sometimes it just runs up higher than normal. Most of th etime I pull over and turn on the heater, and it goes down, and I can drive for a while again before it happens again. Sometimes it doesn't happen again. One time, while on the beach, it ran hot, I turned on the heat and no hot air came out. I can't remeber what I did that made heat come out, but I think it was shifting the transmission in and out of gear. It does tend to run hot more often when riding in the beach sand. I have been slowly losing coolant (about 1/2 gal a month) and a few times low coolant has made the temp guage go up, but it also does it when the coolant is full. There is no visible coolant loss on the outside of the engine, nor in the oil. Does anyone have any ideas or similar experience?

Some History: The coolant was never changed in the first 6 years of the vehicles life and was pretty nasty looking when it did get changed. Looking down the radiator, there doesn't seem to be any excessive corrosion. Have already changed thermostat and Radiator cap. Changing the radiator cap did seem to made the coolant loss less.

My own suspicions: Corrosion in bottom of Radiator than can't be seen causing poor coolant circulation, Partial blockage in cooling system, A stuck valve somewhere in the cooloing system that I'm not aware of, Head gasket leaking into exhaust, Fan clutch faulty: Although it seems to be OK and I experince the problem even when driving on the highway, Water pump impeller "slipping" if that's even possible.

As you can see it's a bugger. If it was consistantly running hot it would be one thing, but the fact that it is intermittent and will run fine for another hour or more before doing it again is really hard to figure out. Any help and/or diognostic ideas would be greatly appreciated. Thanks

Email: bryanttifft@aol.com

[Bakemono]

I think you may be on the right track about the corrosion thing.
Another thing that caught my attention was the fact that you drive it on the beach. Perhaps some sand has gotten packed into your radiator and is reducing it cooling ability.
Ive never lived around an ocean but I wonder if perhaps you could have gotten some salt buildup on your radiator which would also limit it's cooling ability. Ive heard that cars from the coastal states have a tendency to have rust because of the salt that is always present in the air. I would try hosing off your radiator (from the back) and see if anything comes out.
I think it would be a good idea to get a cooling system FLUSH, not just a fluid replacement. I think that may flush out any flaking or corrosion that may be present in the bottom of your radiator.
Cap'n

[burger]

When i first got my 4runner,the coolant was rusty looking-I flushed it about 3 times-it was o.k for awhile and then got rusty again-then i started having the same symptoms as you,which went on for months.then the head gasket really "let go".When i took it out the gasket was all rusted where it met one of the water jackets-old coolant is very corrosive,if yours hadn't been changed in 6 years ,this could be your problem.Get a leak down test done.

[Sidney]

If your engine is a V6 then there is a recall on it,see below.

22 Toyota headgasket & oil sludge recall sites:

http://www.brian894x4.com/V6headgasketrecall.html
http://home.off-road.com/~kemanuel/V6-HG.htm
http://www.showmesome.info/hilux/info/recall.htm
http://www.off-road.com/toyota/4runner/topqs.html
http://www.yotatech.com/~corey/4runner_faq.htm
http://www.thecomplaintstation.com/c...inalrecord=14/
http://www.babcox.com/editorial/ic/ic110028.htm
http://www.alldata.com/recall/make/Toyota_Truck.html
http://www.alldata.com/TSB/60/94601650.html
http://www.yotarepair.com/Campaigns.html (3.4L,V6,headgasket recall)
http://home.off-road.com/~bibelheime...eadgasket.html (3.4L,V6,headgasket recall)
http://home.4x4wire.com/erik/t100/3.4v6_headgasket.htm
http://www.jasperengines.com/pdf/5SFECoolantLeaksTB.pdf
http://www.lemonaidcars.com/secret_warranties.htm
http://www.nordicgroup.us/oil.htm#Toyota%20Sludge
http://www.toyota.com/about/news/pro...-consumer.html
http://www.usatoday.com/money/autos/...ota-sludge.htm
http://www.petitiononline.com/TMC2003/petition.html
http://www.nhtsa.dot.gov/TSBScans/sb621323.pdf
http://www.nhtsa.dot.gov/TSBScans/sb628694.pdf
http://groups.msn.com/ToyotaOwnersUn...gaskettsb.msnw
http://groups.msn.com/ToyotaOwnersUn...adgaskets.msnw
http://www.babcox.com/editorial/ic/ic100052.htm

Sidney
Repairs tv's,vcr's,home/car audio out of my home
E-mail:sidneybek@yahoo.com
Dartmouth,Nova Scotia
Canada
1985 Toyota 4-Runner,22R-E,W56,RN60LV-MSEK,rusted rear step/towing chrome bumper with 244 000 KM

[toyotatifft]

Thanks for the input. I'm going to check the cylinder compression this week to see if the head gasket is bad. Then I'll look at flushing the cooling system real good.

[toyotatifft]

I had my truck checked out by a mechanic yesterday. He could find no visible leaks. His only thought was that there might be a very small leak in the head gasket. He made note of a small amount of condensation under the oil filler cap. He put a small tube of Alumina Seal into the radiator to see if that would stop the leak. He seemed to think that the overheating was probably due to low coolant because these small radiators need to be completely full to do the job. Hopefully he's right, althought I usually filled it up before going on any extended drive. We'll just have to wait and see.

[toyotatifft]

So far, I've gone about 60-70 miles since my last post and I haven't lost any coolant. My overflow resevoir is still at the same mark, which is good because I usually couldn't keep anything in it for over a day.

[burger]

Sounds like you plugged up that leaky head gasket.keep us posted on how long it lasts.I got about 11k miles by doing that to mine.