slight overheating help

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W

W Powell

10 Year
Joined
Nov 10, 2014
Threads
12
Messages
51
Location
Santa Fe, NM
It is cold here currently in Santa Fe and high temps are in the mid twenties. Ironically my truck has been running hot especially at interstate speed under load. The temp gauge is getting right to the red zone but not in it under moderate load.

If I drop it down a gear and rev the hell out of it (same MPH) the temp gauge actually drops to normal???

I replaced the radiator this summer but not the cap. I wonder if I have some air in the lines or if the cap is malfunctioning.

I plan tackle this in the following order and progress as needed

1) Replace cap and burp system
2) Replace thermostat
3) Take to dealer

I just find it strange that revving the hell out of the truck makes the temp go down. Any advice is appreciated
 
@W Powell If I'm not mistaken rev'ing the engine makes the water pump spin faster, perhaps increasing pressure to temporarily overcome any air gap you may have in the system.
 
I forgot the fan clutch. The bearing was replaced last summer as it locked up and broke the belt. I wonder if the whole assembly is typically replaced. From memory it was a 700 dollar job
 
Yeah I'm think your fan clutch has shat the bed. If you have the engine off when cold it should have some resistance if you spin it by hand, and when you initially start the truck it should spin fast and be noisy for a few seconds until the internal thermostat warms up. If it starts quiet on a cold start your fan clutch is bad.

And a weird question... Because your below freezing, have you made sure that your antifreeze is of good quality? Just thinking you would have the same overheating issues if you have blockage from ice forming, or low on fluid. Take a look and report back!
 
Fan/fan clutch won't impact highway speed coolant temps- just low speed operation (<25mph). FWIW If your fan clutch bracket was changed that doesn't necessarily mean the clutch was replaced. Anyway you can check its operation by trying spin it (cold). If it makes a complete revolution or more its probably bad.

This is the first time since you installed the radiator ( several months) its started running hot? Does your coolant reservoir change level hot & cold? Once cooled down for several hours, remove the radiator cap: is the fluid all the way to the top of the neck? If air gap between fins and radiator neck add more coolant.

Did you replace thermostat when you replaced the radiator?
 
When was the last time you cleaned off the radiator?
It sounds stupid,but I know someone who replaced their radiator only to find it caked in years worth of dust
and mud.
 
Highway speeds are usually sufficient to cool the engine without the fan. Around town is where the fan makes a difference. Start with all the stuff you mentioned, the cooling system on these trucks is fairly simple and usually any problems have easy solutions.
 
Check the interior of the radiator. It could be clogged if you didnt flush the system.
You check the coolant flow as follows. When COLD remove the radiator cap and start the engine with AC on to warm up faster. When the engine is at its operating temperature, you can see the coolant flow inside the radiator. Wear goggles FIRST. Rev and see for increase in coolant flow
 
Radiator is new and clean. Fluid is new pink toyota stuff from the summer when the radiator was replaced. I did the radiator myself and all seemed fine. I did notice the overflow tank was at low level when cold this morning and raised to full when hot. I can't say I remember this from before. My memory tells me it was always at the high level even when cold. Engine oil is clean and not milky.

We drove the truck to Cabo San Lucas (all the way down) in August and did have a T in the coolant line give out. Much of the T had desintegrated into the system. A toyota mechanic that I respect told me not to worry about the debris as the impeller will grind it up.?? Replace those T s its is a thing! I attached a photo to show how much of the T desintegrated. I am lucky it happed in a town and not in the middle of nowhere in Mexico Cant tell you guys how much I love this truck. It does so much and does it well.

I will check the interior coolant flow tomorrow. I never have heard of this method of looking inside while running - makes sense. I checked the fan today and it turns at cold idle and continued turning for some time. It does have some resistance when pushed by hand engine off and cold but I do not think I heard any noise upon startup.

I have a new cap, thermostat and coolant. Tomorrow I plan to burp the system and replace the cap. Wish me luck Debri could be clogging the system but it has been months since the T was replaced so I tend to think it may be something else. I am lazy and semi cheap so will start with the easy stuff first. I'll report back. Keep em coming if you have thoughts - thx all

IMG_2918.webp
 
abuck99 - Just reread your post. Fan spins and spins when cold by had but does have resistance. Yes I remember now last year dealer replaced the bracket bearing not the fan clutch I am pretty sure. 700 bucks for the bearing (highway robbery) but I was traveling and not in my hometown.


This is the first time since you installed the radiator ( several months) its started running hot? Yes - except in the line to cross the Mexican boarder in stop and go traffic for one hour in 112 degree heat in August. Turning the AC off resolved this. Radiator was replaced a few months prior

Does your coolant reservoir change level hot & cold? Yes - this is new I think

Once cooled down for several hours, remove the radiator cap: is the fluid all the way to the top of the neck? Yes - Coolant to the top of the neck this morning when cold

If air gap between fins and radiator neck add more coolant. Not at this time - no gap

Did you replace thermostat when you replaced the radiator? I did not - probably should have - HS is 20/20
 
The overflow tank level will fluctuate. That’s normal. Coolant expands quite a bit when hot, hence the need for the overflow tank.

My money is on thermostat.
 
I burped the system and replaced the radiator cap. I did notice coolant movement once warm and a sucking and spewing of coolant with the throttle once warm. Pretty sure the thermostat is opening up. Fan is easy to stop with engine both cold and hot. I grabbed it while warm and it showed no resistance. I will see if I can find a fan clutch locally tomorrow. I drive to CA (3K miles RT) on Tuesday. Wish me luck I am got go for it - we will see.

I assume to buy the OEM Toyota fan clutch. I'm mechanically inclined. Do I have to pull the radiator or possible just the shroud?
 
Thermostat might not be opened up all the way to allow fluid to flow faster? When you rev the water pump is spinning faster causing the system to circulate more? Or could be water pump issue, since you mentioned at hwy speeds so we can rule out the fan clutch. Only thing left to figure out is where the blockage is that's not allowing the fluid to circulate at full cycle. Could be a blocked radiator or partially stuck thermostat.
 
I’d pick up a new OEM thermostat and replace it. It’s easy to do and if you are not sure it has been replaced then it’s a good idea.
 
Def do the thermostat, since I believe the water pump will still make coolant move around in the top half of the system even if the t-stat isn't open.

It's cheap and easy.
 
Cool as a cumber - it was the thermostat.

So easy to change, I feel foolish for not doing it when the radiator was replaced.

I removed the intake tube going to the throttle bottle to get to it. When in there I cleaned the throttle body. Cant recommend cleaning your throttle body enough. Truck is so much smother and has better throttle response

Thanks everyone for your help
 
W Powell said:
Cool as a cumber - it was the thermostat.

So easy to change, I feel foolish for not doing it when the radiator was replaced.

I removed the intake tube going to the throttle bottle to get to it. When in there I cleaned the throttle body. Cant recommend cleaning your throttle body enough. Truck is so much smother and has better throttle response

Thanks everyone for your help
Click to expand...

Glad to hear you got it sorted out. Did you bleed all the air out of the system after you installed the new thermostat? Make sure you keep an eye on the coolant reservoir levels.
 
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