02 DC Taco running hot on highway

Figured there are enough guys here with 1st gen Tacos that someone may have experienced this before.

02 DC Tacoma, 4x4, V6 236k, 3.5" lift, ARB bull bar, winch, canopy, rack, Rocket box, etc.

Truck has been running hot according to my ultra guage since the weather started warming up. This only happens when driving on the interstate for extended periods of time, and is a slow creep. The truck runs pretty consistently around 185 - 190 around town, and if i get off the interstate or stop at a light the engine cools right back down to normal operating temp. Today while driving back from the outer banks heading up a hill the temp got as high as 215 and maintained, and as soon as I crested the hill it cooled down to around 200. It has not overheated and spewed forth the contents of the radiator, but the temp has gotten up into the high 220's when towing a 1100 lb trailer on relatively flat road at 55mph. My initial reaction was fan clutch/maybe my daylighters are blocking air flow through the rad. Took the lights off, and replaced the fan clutch (HD for towing clutch from Napa, Stealership only had the standard orange hub clutch), put in a 170 degree t-stat, and replaced all of the coolant before the outer banks trip and it did not seem to make much difference. The radiator in the truck is brand new as of feb. I installed an ATF cooler in line after the radiator to help keep ATF temps down while towing. It really seems that there is heat build up that the cooling system is just not quite able to keep up with when the temp is above 70 degrees outside. Other than that the truck seems to run really well.

I would appreciate any experience with similar problems/ideas from people. I've considered the water pump, and have not yet had it off or been able to check flow levels. My fear is a head gasket issue, but my coolant looks fine, and im not buring/using/spewing any oil, and the oil looks great even after 4k miles.

And for kicks, here is a pic of the truck on our recent beach trip.

 

When was the last time you had the coolant flushed? Water pump and thermostat replaced? The thermostat has a little jiggle valve on it that should be pointed straight down, it allows the truck to run a little cooler. If it was installed with the valve pointed up, that may be what is pushing your temps up.

That's a hell of a username.

 

I purchased the truck in Feb. I have never flushed the coolant though I drained and replaced the coolant last week. The PO was using Prestone Green so that is what I went with to avoid a gel situation. I dont't have any maintenance records on it, so I do not know when the water pump was last replaced. I personally replaced the thermostat with a 170* unit. I purchased this from the dealer, though it does not have a jiggle valve on it.

As for the user name, I've been a jeep guy for about 15 years and recently saw the light. I however have had this username for quite awhile on a number of other forums, and in the interest of remember how to login I just kept it the same.

 

Interested in the answer as well, I'm having a similar cooling system issue.

My truck normally runs 195-200 according to my UG but appears to get hot linearly with engine RPM. I was coming back from the desert last week up through the mountains and was just watching my UG go from 205 to 215 to 225 to 235, idiot needle was getting mighty close to red. I pulled over and cranked the heat for about 5 minutes. Cooled down to 215 or so, I left the heat on to get up the mtn and when I crested I was back up to around 225...no boil over and still had coolant circulating through the heater core but it seemed way too hot. Ambient temp was maybe 85 and I was chugging up the mtn in 3rd at about 2700rpm, two people in the truck and couldn't have been more than 150lbs of camping gear, nothing towed, nothing in front of radiator, nothing aftermarket.

Previous owner said he had a similar issues with it running hot and replaced the radiator and fan clutch pack not too long ago. The timing belt, water pump, and thermostat were also replaced back in Feb when he still owned the truck. I bought a Toyota 82C thermostat that I plan on putting in to see if it helps (jiggle valve down). I expect to see some weird aftermarket thermo in there or jiggle valve up but I don't think that is enough to explain why it got so hot.

 

sounds like your radiator might have a restriction in it.

give it a good flush in both directions, make sure nothing is blocking the airflow through and to the radiator and if all else checks ok then replace the radiator

 

You guys need to read the whole question, OP said he's replaced both the radiator and t-stat recently so those shouldn't be the problem.

 

I did read it, he said the radiator was new since feb when it was cold and now that its hot its not cooling so maybe they gave him the 2wd radiator instead of the bigger 4wd radiator or the new radiator is plugged up.

if he has air circulation and coolant circulation he changed the stats, all that is left is a restriction in the radiator but he did not mention if he removed the atf cooler he added after the radiator which ,might be blocking airflow if its in the radiators airstream

 

Waht condition are the large hoses in? Soft? Have you replaced them yet? I had a very similar problem on my old 22RE on the way back from a camping trip. I limped home at 55 on an extremely hot night with the heater, never could find anything obvious. Turned out to be a large hose collapsing under suction.
3. RADIATOR HOSE:
The radiator hoses should be in good shape, not cracked, brittle or leaking. Hose clamps should not be over tightened so that they cut into the hose. Other than obvious damage, hoses can restrict coolant flow. Check the routing of your hoses. Make sure they are not routed in a way that causes kinks, pinches or sharp bends causing a partial or complete blockage. Flexible accordion type hoses will restrict the flow and should be avoided.
Another cause of overheating can be a weak, collapsing hose on the suction side of the radiator, usually the lower radiator hose. Located inside of the hose is a spring. The spring is usually located inside of the hose. It's job is to prevent the hose from collapsing. Check this spring and verify that it is in place and that it has not rusted away or simply broke allowing the hose to collapse. In many cases the hose will not collapse until the engine is at higher RPMs or the coolant is hat high temperatures. In some cases a stuck thermostat can cause a hose to collapse so check that as well.

http://www.offroaders.com/tech/engine-overheating.htm

I don't think your hoses have springs, but still the same thing can happen.

 

I appreciate the input from everyone. The radiator was replaced prior to my purchase of the vehicle, though just barely. I test drove the vehicle with the radiator prior to replacement, and the PO noticed that another PO had used JB Weld or some such goop on the top of the rad to fix some type of hole/crack. He decided that he did not want to sell it to me that way. I am not sure whether the replaced radiator was the correct one, though meeting the gentleman I bought the truck from I would imagine so. I have checked that there is no debris lodged in the fins of the radiator. It looks brand new still.

I installed the ATF cooler approx one week ago and noticed no difference at all in the cooling of the engine one way or the other. As of right now I do not have an ATF temp guage so im not sure the difference it has made on the tranny.

It could possibly be the lower coolant hose. It is getting on the soft side. I was planning on replacing it when I did the thermostat but Napa did not have the correct hose and I needed to get on the road.

I dropped the truck off at the shop I occasionally use here for them to see what they find. We are getting ready to move from Virginia to Colorado in less than two weeks and I will be towing a 6ftx12ft trailer. Needless to say its a very high priority to have this problem sorted out.

 

I've been dealing with the same thing for a year now. Not so much in the winter but I'm seeing it again as it warms up. I had the water pump and thermostat changed last fall along with getting the coolant flushed but it still does it.

I'm thinking its the jiggle in the wrong position or a hose collapsing. The max I've seen is 215, but as soon as I crest a hill or coast down a hill it will drop to 195. Other than that it will be pretty consistently around 200-208.

 

Yeah for normal driving its not a huge deal, but im getting ready to move across the country towing a trailer, and I am a bit worried about that.
My mechanic drove it and seems to think my ultra guage is pulling temp from somewhere other than the engine coolant temp sensor and thats why its giving me a high reading. I do not think he is correct in that assumption.

 

Just did a quick run on the highway and got up to 208 on the UG when going uphill in 3rd @ 2600 or so. I pulled off and into a parking lot. Fan was on and seemed to be pulling good air, could feel the air flow on the grill side of radiator. Put my hand on both inlet and outlet radiator hose...top inlet hose to radiator was definitely hotter, lower radiator outlet hose was much cooler. Only thing I can think is that thermo is gummed up and not opening all the way. Just seems like the cooling system can't keep up with the engine for some reason. Guess that could be a number of things....

 

I bought a new radiator cap because I noticed it my old one had a cracked gasket. New one didn't help. Got up to 214 coasting 1800 rpms at 6pmph. it drives steady at 204 degrees if I turn overdrive off though, which put me around 2300 rpms at the same speed.

 

I had the radiator flushed yesterday and installed a new lower rad hose. Took it for a spin last night on the highway and it didnt get above 186, though it was only 62* outside so I'm sure that had something to do with it. I took it for another drive just now with my trailer attached and doing 65 on the rolling section of interstate it got up to 208. Today isn't nearly as warm (74) as it has been the last few days so I'm not sure how I feel about 208. I did have the AC on the entire time, and once I crested the hill it started cooling off. My concern is running uphill with a trailer on a 95 degree day might put me in the 225-230 range which is definitely hotter than I would like to run.

The shop I took it to for the flush generally does good work. They said they did a block test and everything came back good.

 

When was the last time you decarbed your engine? When was the last time you did a compression check?
High cylinder pressures from excessive carbon build up will cause over heating especially with a load.
A semi restricted catalytic convertor or exhaust will do the same.
Radiator=good
Lower Radiator hose = good
170 degree thermo = good

 

When you say decarbed what do you mean? And I have not done a compression test since I've purchased the vehicle. I will definitely look into the cat. I'm running reasonably unrestricted exhaust (18" magnaflow dumping down below the truck) but I am not sure about the cat. Any way to tell without pulling it out of the exhaust?

 

Should be able to check the temp of the exhaust pipe before and after the cat with a thermal gun. It should be considerably hotter after the cat I believe.

 

so in your opinion what was the net result of getting it flushed? running a few degrees cooler or about the same?

 

I think it is running a few degrees cooler, especially on the highway, though I'll admit that the ambient air temp has cooled off 10-15 degree since I had them do the flush. It was in the mid 80s the days leading up to it being in the shop, and the day I got it back it cooled off considerably and is not in the low to mid 70s. So what I have noticed is it consistently ran around 190 - 192, now its running around 186. Whether that is a result of the flush or just the cooler air temps I am not sure.

 

Fan clutch. Under load, up hill will make the temp rise if the clutch can't keep up it will cause it to overheat.