Tundra running hot - Advice badly needed!

Ok, I’m stumped and more than a little worried, and I could use some experienced suggestions.

Short version:

My 2011 5.7L Crewmax with 136K miles just started running hot while driving up the mountain on which I live. It doesn’t overheat, but it does get uncomfortably close, running at 3/4 on the temp gauge. It never used to top 1/2, and still doesn’t under any other circumstances. Heat behaves normally.


Long version:

Three days ago, I drove up the mountain (about a 1500 ft elevation change in a couple miles of road), and noticed the gauge climbing. It was just over 3/4 when I got home. I got out of the car, and popped the hood. The coolant in the overflow was at full level, and boiling, with steam coming out of the overflow pipe. Not good!

After it had cooled, the coolant bottle was near empty. I opened the radiator, and coolant was low. I added two quarts. Since I could not see any leaks anywhere, I figured it was a bad radiator cap that had caused the fluid loss and boiling, and replaced it.

The next day, all was well on the drive in to school, and it never topped 1/2 on the gauge. I had heat within five minutes of driving. Outside temp was about 34 degrees. I checked it when I got to school. No overflow, no boiling, no weirdness.

On the way home, all was similarly fine . . . until I began the climb up the mountain. The temp gauge began to climb after the first hill, and gain got to the 3/4 mark by the top. This time, however, there was no overflow, and no boiling in the coolant bottle. I checked it with the engine still running, figuring that if it was a blown head gasket, it would bubble in that tank with the engine running. It did not. No bubbles. Again, no visible leaks. I did a squeeze test on the upper radiator hose, and it was full of fluid and hard to compress.

On the idea that I might have an air bubble, I let it cool and “burped” it, running it for a few minutes with the front elevated and the radiator cap off. Both at idle and with engine revved to 3K, no bubbles evident, though some coolant did splash out when I revved it. Replaced the cap and shut her down.

Today, the exact same scenario. Fine all the way to work, and all the way home until the mountain. . . then the temp spike coming up. Again, NO bubbles in the overflow tank. Now here is the really weird part. When I got home, with the temp gauge at 3/4, I didn’t turn it off right away. Instead, I revved it while parked. Hit a little over 3K. When I did so, THE TEMP DROPPED IMMEDIATELY, all the way down to UNDER 1/2. I am assuming this means it isn’t the head gaskets, since at that rpm, if it was forcing exhaust gas into the coolant, the temp should have gotten worse, not better, no?

It’s also worth mentioning that there is no white smoke from the exhaust.



Ok, if you’ve read this far, you know all that I do. SO . . . any guesses what is wrong? The radiator cap is new, so that isn’t it. Bad thermostat? Bad water pump? Bad fan (does it have a fan clutch?). Dreaded head gaskets? I could really use some experienced pointers here at what to look for. Any help is greatly appreciated!

 

It sounds like you might have air trapped in the system sometimes it’s very hard to burp system and it takes time I’m going to tell you what works for me and I just did it today on a Nissan Exterra and have done it on hundreds of cars in my career.
This Tool is Great I have 2 of them will make burping much easier and less messy
I use this funnel and fill it half way with coolant with the vehicle running heater all the way on high and hot engine RPM’s at 1800-2000 steady for a couple minutes you will see all the air bubbles coming out and it will suck in coolant then let it idle and settle down and do it again always have the heater on high and hot like that the heater valve is open and heater core will flow coolant and trapped air will work itself out

 

I had a thermostat go bad that caused the exact same symptoms you are describing. This is an easy and inexpensive replacement. You might start there.

Dan

 

Well, no smoke is a good thing. Short of the system still having air in it... Is your belt to the water pump tight? Spin the radiator fan by hand and see if it spins too much. There should be resistance. If you have one of those IR cooking temp guns you can always point it on the thermostat housing or the return line just before the radiator to try and help rule out the thermostat. I don't know about Tundra's, but in other vehicles once one cooling component goes, it's a good idea to go ahead and replace the thermostat, pump and hoses and any other components that are prone to leaking/failing as they're now the weak point in the system.

 

I would do a simple cooling system maintenance first. As was already said here, change the thermostat and flush the cooling system. Use that spill proof funnel. It's invaluable. This will all be relatively inexpensive and will knock a couple of things off the maintenance list as well as help diagnose this issue.

 

If you remove your thermostat from your truck and it’s OPEN then the thermostat is bad a thermostat is always CLOSED until it reaches operating temperature so you can check that as well like Bergman said

 

Thanks all!

It looks like I'm doing a thermostat change and a more thorough air-elimination this weekend. It's simple and cheap enough, certainly.

It is worth mentioning that the red coolant looks quite clean, so I'm no leaning in the direction of a dirty or clogged cooling system (though I guess I could be wrong)

I'm in terror of it being a head gasket; I know that the lack of white smoke and/or bubbles doesn't **definitively** rule that out. I would think, though, that if that was the case, the temp would not have dropped that sharply and immediately upon me revving past 3K in the driveway, no?

I'll change the thermostat and burp it again and post an update.

 

It might be inexpensive, but you need tiny hands to change it. It'll fight ya.

 

If you have heat right away, then the tstat is not stuck open.

 

The mountain climb should self burp the rad. My guess is the thermostat is stuck.

Good job on replacing the rad cap as they need to be changed every 5 years just because of wear and its cheap insurance. Cheaper than a pressure test.

 

Yeah, my T-stat failure was on my Gen 1 Tundra. I had everthing all apart during the timing belt replacement and decided to change it out then. Not familiar with the T-stat on my Gen 3.

Dan

 

Long-overdue update:

Shortly after my original post, she developed a pervasive whir/whine noise from the belt area, which got louder over the next few days (although the temp issue did not get worse - still only on load up the mountain, and remediable by dropping to lower gear/higher rpm). Although it was impossible to pin down for sure, it did sound like it was coming from the top-front passenger side of the block, where the water pump is, so it definitely had me leading towards that as the issue.

I parked it for winter break (I teach high school) and then took it in to the school shop when I returned. Free work by a talented bunch of award-winning seniors under a ASE master tech is one of the few benefits of my job. I like to do my own work, but they have a heated, well-lit garage, and I'd have had to do it in a freezing, sloped driveway, so I took the easy way out this time. Although it wasn't the approved one-thing-at-a-time trouble shooting method, I just had them replace the fan clutch, water pump, and thermostat together. Getting it done quickly was more important than tedious trouble-shooting. With free labor, it cost me about $275 including a new belt and 2 gallons of antifreeze, so it wasn't too bad.

The good news is, the overheating is gone. Unfortunately, because I had them do several parts at once, it’s impossible to tell which one of those parts was the culprit. Given the behavior and the increasing belt-whine, though, I’m strongly inclined to think it was the water pump. The Auto-Tech teacher is of a similar opinion. So, if this happens to you, that's what I'd suggest to address first.

Thanks for all the advice and help!

 

Good to hear you got that fixed.

 

Sounds to me like your clutch fan was the culprit. The reason I say this is when you revved it up it cooled off. Driving up a steep road you were probably not getting enough air flow across the fins to control the temp

 

It is certainly possible, Sunfish, but I wonder if that would have caused that ever-increasing belt/pulley/bearing whine?

In a perfect world, I'd have done that first and then checked the results . . . but I needed her back on the road, so I just went with overkill and did it all. Oddly, the fan clutch was the more expensive of the parts (although easier to replace by far).

 

The fan clutch is one of the easiest things to identify as bad. When started up cold you should hear the fan blowing for a few seconds. If it doesn't replace it. When the truck is hot, to the point of almost boiling over the shut the engine off and try to turn the fan. If it spins freely it's bad.

 

Doing what you did on a truck with that many miles was just a smart move. The water pump and thermostat are wear items and need replacing. Sooner or later the water pump was going to fail and leave you stranded. I would also replace the belt if there's any signs of age or if it's more than a couple years old.