Thermostat or radiator?

Hi, my 2007 5.7 Tundra overheated yesterday. Got it home and changed the thermostat.. same issue. has never leaked at all, no real sign today of that as the coolant is full and clean. Upper radiator hose is way too hot and lower is cool... My guess is radiator issue or a failed (new) thermostat. Any thoughts?
Mike

 

Or water pump

 

no sign of any leaking from the pump. I'm not sure how to check it otherwise.

 

It mY have been the thermostat but now you have a air pocket let it cool take the rad cap off start it and squeeze/pump so to speak the upper road hose till it gets to operating temp either a tad is good or bad. Unless it’s clogged. Which I doubt

 

Wondered about the fan clutch, but no noise from it and the hoses being so dramatically different in temp made me believe its the flow of coolant. about to go out (waiting on rain to stop) and check the "squeeze the hose" test, try to eliminate any air pockets.
MG

 

Air lock could also be in heater core and aiding to air in system issues. Place heater in full heat while testing to eliminate this possibility.
Good luck!

 

You can also test the fan speed by putting a piece of paper in front of the radiator. If it stays then the fan is pulling the right amount of air. If it falls, then it’s not turning at the correct speed. But it doesn’t sound like the fan cause of the difference in hose temps.

 

Thanks for all your help. manipulated the upper hose and the lower hose while the car warmed up... without much indication the lower hose began to warm and the temp stabilized at normal. It was late last night when i finished up, but will run a better road test this morning. Fingers crossed... going to be difficult to get out of the hurricane's way if I can only go 1/2 mile at a time!!

 

Good morning...
initial road test went great, temp stayed just below half. But on the way back from the store, jumped to about 3/4. Pulled in and the coolant res. was boiling, over max and spraying. During all the idling the coolant stayed at 1/2 between low and max. The upper hose is roasting and the lower was, again, much cooler even through 30 min idle they pretty much stayed the same. Thoughts?

 

Get a new cap, easy to eliminate and inexpensive.

 

It's been a while since I've done this. But try it.. Start engine when cold, remove radiator cap. As it warms up and the thermostat opens you should be able to bring up the rpm's and watch the coolant move. When you bring up the rpm's you should clearly see the coolant move. If the coolant barely moves then it is clogged..

 

Where are you watching it move? With the cap open on the radiator, not the reservoir, I can see the upper internal guts, but do not see any coolant much less any moving. Just checked it again on a short drive, temp stayed at 1/2, but lower hose is still cool to the touch. Is that normal? Upper hose is very hot.

 

Sounds like you got a water pump problem. Water pumps don't have to leak to go bad. Impeller could be off etc. Not sure how you can see the coils unless your looking through the coolant and seeing them. Could be a defective stat. Take it out and run without if possible

Your truck is old enough that it wouldn't hurt to pull down the cooling system and take the radiator to a shop to test and clean. Over heating an engine is not something to play around with.

I just reread and see you could be in a bind with this and my suggestion may not be good for the short term.

 

Yes, through the radiator cap not the reservoir If you can’t see coolant then you are definitely low.. I have never experienced a broken water pump impeller or a bad thermostat..Not saying it can’t happen just that I have never seen it..

 

Thanks. I may have to pull it. I added enough coolant to be seen above coils, but can't see whether it flows or not. The coolant we drained when replacing the thermostat was clean so I don't think debris inside would be bad. I will get the cap as soon as I am at the store again. And, yep, until Dorian has passed my options are limited, but at least I have a couple of days to work on it here.

 

I thought I was having a issue on mine when I brought it home as the level wouldn't hold. On the 2015 you can't see the coils and it flowing. But what you do notice as the system heats up the fluid expanding and over flowing into the jug connection. Had it pressure tested and just a huge air bubble that amounted to almost 3/4 gallon of coolant till it finally cleared up but never an issue with overheating on it.

FWIW wife's 2006 Lexus fried the radiator about 4 years ago.

 

Especially an aluminum one.

 

A simple test for the fan is when you start it up cold. It should sound like it's blowing air for a few moments until it warms up and then it'll quiet down. If it was me I would just break down and replace the water pump, the fan clutch and radiator cap. Use quality parts. 12 years old and if they've never been done before it's worth doing them. The most important thing is to not damage your engine or you are going to run into large bills to repair it. I even thing the radiator isn't that expensive but unless you look inside and see the internal cooling tubes corroded I would wait. Besides when you do the water pump you'll most likely pull the radiator so you have extra room to work and then can get a much better look at it to see if there's damage (once had one where the external fins rotted away on the bottom half).

 

I was curious and looked at a radiator on Rock Auto. $120 ain't bad for a brand new Denso. Iffin I was going that far to pull it out, I'd sling a new one in at that price.

 

Thanks to all. Went on a hurricane prep outing and coolant boiled out again. Only hitting 3/4 but that's too high a temp. When it cooled I checked the hoses and still too hot on top hose and cool on lower... seems like no flow. Funny thing is it stayed cool at the first two stops, it was after the third that the temp climbed.
I'll get the new cap and water pump as soon as I can.
Thanks again.

 

Remove the thermostat and see if you're getting the same problem. I've never seen a belt driven water pump not move water, the bearings will break and make a ruckus of noise before the impeller breaks which usually following a broken bearing causing it to misaligned and slap against the inlet.

 

Thanks for all your help! Here's the update. jeremyd, you hit the target. I bought the pump, gasket, and cap. Went to replace the cap and had not noticed that the bottom stopper/cap was missing on the old one. Im guessing it broke down and allowed the initial overheating issue. The first thing i did was replace the thermostat, so that's done. Now it runs fine, made it to work for a week, but will hold at normal, but creep above half on temp gauge. It usually will drop back down, but is still higher than normal. Im guessing the missing part of the cap is blocking flow or impeding flow somewhere... anyone had that issue. will draining from the lower hose allow the part to exit? the cap is about nickel size, the drain port is only about dime size, so that's out. Any suggestions?
Mike

 

Yes. Replace the two easy items--thermostat and cap-- and then think about replacing the radiator itself. 209,000 miles tells me you're in the life span probability zone.

 

Thermostat and cap are new ( two weeks old, cap is one week old) . Radiator is clean inside and removed fluid is very clean. The truck has never had a single temp issue until the cap broke. Now I've got the lower parts of the old cap inside, I'm pretty sure. She's not overheating, but running above half which is not normal. I'd rather not replace the radiator if its not absolutely necessary.

 

The truck should hold dead-steady needle position on the temp gauge as you drive and load the engine to various degrees. 209,000 miles, in my book (life's experiences) is in the radiator replacement zone. Most wait for a physical leak to spring, get stranded, and then replace under duress. You have a chance to avoid all that shiznit. Does your money allow you to buy a good new replacement radiator?

 

Already had the duress, but the radiator has no signs of any issue. Money is always tight, I'm a teacher. Basically, I feel I've already wasted $ on the thermostat, pump and gasket when I wasn't sure of the issue. Now its pretty clear the reduced flow is from the parts that have fallen in. Just need to figure a way to get them out or force them back to the top.

 

What ever is clogging it, I don't think will come out of the bottom..My gut instinct says replace the radiator.

edit : The fluid may look clean but internally the radiator water jackets may be clogged..

 

Is there room for two in this ^^^ boat???

 

I already know there’s not room for the two, I’m just trying to be nice to the dude..

 

If you’re trying to flush something out and radiator looks good you can always pull it and flush it. Whatever you think is in there should come out either the bottom hose fitting or top hose fitting.