ridewrapper

I have a 1995 4runner that runs pretty much flawlessly it has 167k on the motor and the head gasket has never been done. I can sit in LA traffic for 2 hours straight and it has no heat issues. I went up a steady incline, maybe about 5 miles long at most and it starts heating up. The temp always runs about a needles width less than the half way mark on my temp gauge. I let it get to the heavy side of the halfway mark and I turned the heater on to make sure i didn't pop a gasket as a I hear they hate heat. As soon as I cleared the hill it ran flawlessly again at the temp range it always runs at. No codes are showing, It just passed CA emissions with incredibly low numbers so I know the Cat is fine. Any suggestions?

Also where should the temp needle be allowed to reach before I pull over so I avoid a costly head gasket replacement? Where does a 3.0 Typically run in the stock temp gauge?

Gamefreakgc

A 3.0 typically NEVER moves past the halfway mark. The fact that yours does means you've got an overheating issue. I can climb all the way up 8000 ft in the Sierras without it budging, and that's with 284k miles.

I highly recommend a full coolant flush (not just draining the radiator, search it on google or follow directions) and possibly even changing out your thermostat located at the end of the lower radiator hose. Also, there's debate back and forth on what coolant to use. I had green coolant and it started corroding my radiator. I switch to Toyota red (what the dealer recommends) and have had no issues since. If you have green in there and it looks rust colored or has flakes of rust, change to red.

ridewrapper

That sounds like a good idea that is routine maintenance and needs done anyway. But...Why can i sit in traffic all day and it not overheat? Even if i go wheelin it never gets hot. Does that prove the thermostat works and the coolant system flows well?

snobdds

With all cooling issues, the first step is to preform a coolant pressure test.

Then find if it hold pressure and if there are any leaks. The go from there. This will prevent you from not diagnosing the problem correctly and spending unneeded money.

RJR

When you're idling in LA traffic or out wheeling, you're probably burning about 1 gallon of gasoline per hour. Going uphill at 60 mph may push that to 5-6 gallons/hour. That's 5-6 times more heat your radiator has to get rid of. No surprise it heats up more, and I would expect the temp gauge to move up a bit. In general, the hotter the water temperature in the radiator, the more heat it can dump to the air flowing through it.

How fast is your engine turning when you go up the hill? Are you keeping the rpm's up around 3500-4000, or are you trying to lug up the hill at 2500 rpm? Higher rpm's will cool better because the water pump is moving more water and the fan is moving more air.

Unless your temperature gauge is moving dramatically over to the hot side, I doubt you have a problem. Serious overheating of the engine doesn't occur until you start boiling coolant away. Up until that point, nothing's getting hotter than about 250 degrees (the boiling point of coolant with a 14 psi pressure cap on the radiator), which isn't going to stress the metal parts of the engine, or the oil, significantly.

ridewrapper

I was going at the hill at about 3000 rpms took the OD off it jumped to about 4000 rpms then the temp started climbing. Put the OD back on speed went down and temp started going down im not sure if it was the heater going on or the OD going back on that brought the temp back to normal. It seems like that from what I've been reading that it doesn't take serious overheating to slip my head gasket though. maybe I'm being overly terrified of seeing that needle creep up?

Gamefreakgc

If you can, do it. The factory maintenance schedule says to replace the coolant every 2-4 years, depending on usage. So if you haven't, do a good flush. Coolant that has started to break down won't transfer heat as well and you risk ruining other parts like your water pump and cylinder head & gasket.

snobdds

There is no if you can do that, you must. What good is new coolant if there is no way the system is holding pressure.

ridewrapper

Okay, so just a tiny leak could cause what I'm experiencing? I mean tiny! I got to digging and it is a hose that looks like it was cut and reused as a smaller hose. The leak looks like it is a drop from an eye dropper size.

Inu

Mine gets warm coming from Victorville to cajon pass southbound. No where else. Adding a trans cooler helped take the cooling load of trans off. Check that your rad is full cold and that some is in the overflow, condition of the coolant, rad cap holding proper pressure. Caps pretty cheap.i just take od off set cruise at 55 on that grade now.

ridewrapper

That's the Hill I'm talking about! Cajon pass. My problem is north bound 15. I even tried to bypass it by going around on 138 its a steeper hill but a ton shorter. It was reacting the same in both routes. Going down hill though my 4runner seems to be fine tuned race car. I have the 4:88's I can take off the OD and do 65-70 but thats when it gets hot. So I took it off and was able to get behind a semi and crawl up the pass.

Inu

Yea same 4.88 31s. Just south for me. North it seems to do fine. Just get in the second lane shut od off 50-55

ThatGuy1295

Sounds weird. If everythings right that needle should never move past half way. Heck my 3.0 leaks coolant out the radiator hose and never moves past half way. Soooo, only one guy mentioned getting a new thermo stat because yours is obviously not opening all the way. Hmmm.
Start there.

Gamefreakgc

Uhh... overheating is not normal. Don't ignore it, unless you like changing blown radiators and head gaskets.

vital22re

iTrader: (2)

Your fan clutch may be starting to slip at high rpm.

j2the-e

Sounds like a blocked radiator to me. Here is a trick: take the radiator cap off (when cold of course) and an old wiper blade. Take the blade apart. The blades have a metal insert on either side of them(most older toyota blades do anyway). See if you can stick the insert all the way down the radiator tube. If its blocked, it needs to be rebuilt or replaced. Flushing is a waste of time and money to cure a blockage

j2the-e

I'd like to add that that test is not 100% definitive. If the 2-3 tubes you can access are clear, it doesn't meant you have no blockage. But if they aren't clear, the others are probably plugged too. A better test, if you have the tool, is to run it for 5-10 minutes and shut it off. Using an infrared temp sensor, run it across the engine side of the radiator looking for cold spots

RSR

The OD/auto tranny/hills is what you all are overlooking...

It very well could be (and I think it is) that your tranny was overheating your coolant!

OD on hills isn't much different than towing in OD... It can overheat and overstress your auto tranny...

Definitely get an auxilary tranny cooler on your rig and -- only if adding a tranny fluid temp gauge to keep track of temps -- consider bypassing your radiator tranny cooling tubes altogether once you get a baseline temp reading with factory setup to compare.

Running an auxilary cooler will also prevent pink slush/ruining your tranny when your radiator eventually fails...

RSR

Btw: https://www.yotatech.com/forums/f2/overdrive-off-14038/

Essentially for our generation of trucks and the OD switch -- as I understand it, the tranny fluid pump speed is directly correlated to engine RPMs. With the load of towing at low speeds, the tranny pump isn't pumping enough fluid through the tranny to keep it from overheating with the additional load being placed upon due to the extra weight being towed -- hence the OD switch and 3rd gear causing/forcing the engine and tranny pump to run at higher speeds to provide adequate cooling. Typically, it's the 45-60 mph range that's the issue I think (higher than that and engine is running at high enough RPMs to keep the tranny cool -- but don't quote me on that, just hearsay/if you ruin your tranny it's due to your own decisions and is your own fault not mine...). Regardless, yet another reason to go w/ synthetic fluids (once again, Amsoil is one of if not the best option for you as it takes a lot higher temps to compromise its fluid).

Additionally, on hills the auto tranny in our trucks tends to shift in and out of OD (between 3rd and 4th gear) unlocking and locking the torque converter which creates a lot of heat. That heat then flows from the tranny to the oil to liquid cooler in the bottom 1/4 or so of our radiator (engine coolant cools tranny fluid) which heats the coolant as tranny heat is transferred to the coolant -- this immediately before the coolant leaves the bottom of the radiator for the engine to restart its cooling cycle (far from ideal)... And you also have the engine/tranny under load issues discussed above that are not that much different from towing a trailer.

For newer generation trannies, this engineering "flaw" and/or compromise was made more bulletproof with adjustments to tranny cooler flow rate -- I think more electronically controlled and less mechanical but don't quote me. And this change was also necessitated in no small part to folks not reading their owners manuals and destroying their trannies...

And this is more related to my previous posts, but most tranny shops recommend external tranny coolers installed in sequence with factory setups but they recommend radiator then oil cooler to ensure lowest possible tranny fluid temps.
The Toyota towing package setup for our trucks included an oil cooler, which I have on my truck. It's not the best oil cooler nor mounted in the best location (one of my old posts in a thread about tranny coolers discusses and has pics -- you can dig through if you're so inclined), but it's installed tranny to oil cooler then radiator then back to tranny. My original thought was primarily to ensure a consistent oil temp/viscosity, but it also makes sense from a not letting an overheated tranny overheat your engine perspective as well.

*Please note I'm using "oil" and "fluid" interchangeably -- but referencing transmission fluid/ATF...

ridewrapper

Is this how your temperature gauge reads after an hour of freeway driving?





This weekend I'm going to pressure test, replace the upper hose either way. Mine has a drip and I have one on hand. Then go from there.