Slightly overheating and heater blows warm air

[cj80cruiser]

I changed my radiator in September of 2011 with a koyo and about the same time I bought an Ultragauge to monitor my cooling system temps. At the time I should have changed my thermostat but didn't think about it until I already started draining the old radiator. I figured it was probably fine for the time being and continued on with the new radiator and fresh fluids.

Fast forward to last summer when I made a trip to Monroe, ga (about 2 hours away all interstate) and my temps got all the way up to 213 degrees when I stopped at the traffic light off the exit ramp. Most of the trip I was riding at 208-210. This didn't raise the needle on the OEM gauge much if at all.

My temps are now consistently around 199 compared to last winter at 194. I'm still in the green at those temps but I also noticed my heat didn't get as hot as it should minus one day this winter when it was really nice and hot like it should always have been.

I'm leaning towards a sticking thermostat which I'm going to go ahead and replace today.

Could this be my waterpump on the way out? I havent heard any unusual noises coming from the pump. The timing belt was changed at 68k, not sure if the water pump was changed too as I didn't own the truck at the time this was done. I'm sitting at 128k now and was going to wait until I hit 150k.

 

[BlackCat914]

213 should not be any concern. Make sure you have good flow going through the heater core, and that there is no debris blocking it on the outside.

 

[cj80cruiser]

213 should not be any concern. Make sure you have good flow going through the heater core, and that there is no debris blocking it on the outside.

By make sure no debris is blocking it from the outside you mean to make sure there's nothing blocking/clogging the lines at the firewall? Am I understanding you? Sounds like a good idea.

I wasn't so much worried about the temp as I knew it wasn't ridiculously high. My concern is the change in temps from one year to the next combined with the heater only getting warm. Thought maybe the thermostat might be restricting the flow.

 

[02_SE_Runner]

By make sure no debris is blocking it from the outside you mean to make sure there's nothing blocking/clogging the lines at the firewall? Am I understanding you? Sounds like a good idea.

I wasn't so much worried about the temp as I knew it wasn't ridiculously high. My concern is the change in temps from one year to the next combined with the heater only getting warm. Thought maybe the thermostat might be restricting the flow.

Do you know your exact driving pattern/temperature/humidity from year to year? Unless you had a controlled variable from year to year, there is no way to tell if you would be running hotter or colder unless you had the EXACT SAME variables this year then from the last. Maybe your heater is hotter, because it's hotter outside?
/.02

 

[JEL]

I recently ran into a cool heater issue intermittently, but mine turned out to be the servo for the 99+ Limited auto climate controls. One thing I would also check is the condition of the condenser, make sure it's clear as BlackCat914 mentioned. Also, I think you're on the right track with the thermostat, but check out the fan clutch. I'm not sure if you can do the magazine test on these trucks, but at the very least I would ensure it doesn't wobble when the engine is on or off. A bad water pump can also do things such as this, if the impeller has begun to degrade it'll provide less cooling and less flow, especially at idle. This happened in my 7.3 Powerstroke truck from the silicate (essentially sand) drop-off in the antifreeze.

 

[Grenvilleter]

For some reason, i'm thinking a partial air lock in the heater core. I think you could tell from your temp monitoring if the t'stat was sticking.

 

[cj80cruiser]

For some reason, i'm thinking a partial air lock in the heater core. I think you could tell from your temp monitoring if the t'stat was sticking.

I guess I would see a fluxuation in temps soon after I hit 180° on my ultraguage if my thermostat was opening all the way right?

Do you know your exact driving pattern/temperature/humidity from year to year? Unless you had a controlled variable from year to year, there is no way to tell if you would be running hotter or colder unless you had the EXACT SAME variables this year then from the last. Maybe your heater is hotter, because it's hotter outside?
/.02

It hasn't even gotten close to how hot its going to get this year and I'm already running hotter than last year.

 

[Grenvilleter]

I've watched regular temp gauges rapidly fluctuate when a stuck t'stat opens and if it sticks shut, you really notice it fast with the heat gauge climbing rapidly. With real time temp monitoring like you have, I would think you could almost tell when a normally working t'stat opens up.

I've had too light an anti-freeze mix and when the real cold weather starts, it was very easy to tell when my t'stat froze shut. The engine temp would shoot up quite rapidly and when the t'stat thawed out and opened, the temp would decrease just as quickly. I was lucky and shut down the engine when the temp started going up rapidly and sitting for 5 minutes shut off allowed the t'stat to thaw and open. Temp decreased just a quick when I started the engine again.

The lack of heat from the heater makes me think air lock and although it is partially working it don't take much of a bubble to interrupt the whole system.

 

[robb1887]

If your radiator was clogged up and required replacement chances are if you ran you heat at any time around the radiator needing replacement, whatever clogged your radiator is gunking up your heater core(s). I ended up having to replace both of my heater cores this winter because the heat just didnt work at all. This was after doing a major cooling system overhaul the previous fall and the summer let all the gunk settle in the fins. As far as "not getting as hot" check the valve on the firewall to make sure its operating completely.

 

[LittleCaesar]

Have you grabbed all the coolant hoses once the 4runner is really warmed up? If one is cold, then you can pinpoint your problem area.

If you don't know if the water pump has been changed, I'd do so sooner than later. How is the fan clutch?

 

[cj80cruiser]

If your radiator was clogged up and required replacement chances are if you ran you heat at any time around the radiator needing replacement, whatever clogged your radiator is gunking up your heater core(s). I ended up having to replace both of my heater cores this winter because the heat just didnt work at all. This was after doing a major cooling system overhaul the previous fall and the summer let all the gunk settle in the fins. As far as "not getting as hot" check the valve on the firewall to make sure its operating completely.

It wasn't clogged that I was aware. I changed to prevent the pink milkshake. The coolant needed to be changed and I ran several gallons of distilled water through it. Then parked on ramps, let it cool down, opened the radiator cap, and started it back up to burp it. I did this several times to ensure I got all the crap out but it's possible 2 winters later it something broke free and clogged the heater core.

I hope it's not the heater core. I loathe the idea of removing my dash but thats just me being lazy.

I've watched regular temp gauges rapidly fluctuate when a stuck t'stat opens and if it sticks shut, you really notice it fast with the heat gauge climbing rapidly. With real time temp monitoring like you have, I would think you could almost tell when a normally working t'stat opens up.

I've had too light an anti-freeze mix and when the real cold weather starts, it was very easy to tell when my t'stat froze shut. The engine temp would shoot up quite rapidly and when the t'stat thawed out and opened, the temp would decrease just as quickly. I was lucky and shut down the engine when the temp started going up rapidly and sitting for 5 minutes shut off allowed the t'stat to thaw and open. Temp decreased just a quick when I started the engine again.

The lack of heat from the heater makes me think air lock and although it is partially working it don't take much of a bubble to interrupt the whole system.

My heat tends to rise at what I would consider normal. It takes about 3-4 minutes to rise from around 40 to mid/upper 100's.

I feel liked I burped the system pretty well by parking on ramps and letting the truck run for a while with the front elevated about a foot or more since it was on a slight incline. I ran through all my heat controls at the same time.

Have you grabbed all the coolant hoses once the 4runner is really warmed up? If one is cold, then you can pinpoint your problem area.

If you don't know if the water pump has been changed, I'd do so sooner than later. How is the fan clutch?

I really should have taken a second today and checked the fan clutch. I ended up losing my opportunity to work on the truck today due to my twins acting up. My wife and mom took them shopping but they were so ill that they brought them back home and put them in the bed. Then they headed back out without the twins.

Anyway, i'll check the clutch tomorrow....my wife owes me one.

 

[Grenvilleter]

"I hope it's not the heater core. I loathe the idea of removing my dash but thats just me being lazy."

Sure don't blame you there ! I HATE that job.

As LittleCaesar queries, check your heater hoses and try to determine if there is much difference.

If your heater blower motor is not running, hoses should be the same temp (almost). Make sure you have the temp control in the cabin set to maximum. If you start the blower fan and can detect the return line a few degrees cooler, you might be light on flow and consider changing the water pump but again, it could be partially blocked

If they are the same temp, you can try to back flush the heater core as a stand-alone unit thus keeping track if any debris ends up in your catch basin.

If you have one of those laser temperature readers(they are quite cheap now ) this makes your job really easy.

Just measure the 2 heater hoses and coolant temp in the rad itself and those numbers will tell you if you have to flush your heater core or change your water pump or just burp it more thoroughly.


In the absence of a laser thermometer, I'd do the easy stuff first by re-burping the heater core
Throw a rag over the loose coupling so you don't spray anti-freeze all over and then start the truck and bring the rpm's up to 2500 and hold it for a few seconds (15-20) and watch for air escaping.
If the flow seems strong, & steady, tighten 'er up, check your reservoir, tighten your rad cap and try it out again.

Just a thought...did you change your rad cap when you changed rads? You might want to do that regardless.

If you are not in stop & go traffic, regular airflow through the rad should keep it cool enough with no fan so but it would be remiss to not inspect.

 

[cj80cruiser]

"I hope it's not the heater core. I loathe the idea of removing my dash but thats just me being lazy."

Sure don't blame you there ! I HATE that job.

As LittleCaesar queries, check your heater hoses and try to determine if there is much difference.

If your heater blower motor is not running, hoses should be the same temp (almost). Make sure you have the temp control in the cabin set to maximum. If you start the blower fan and can detect the return line a few degrees cooler, you might be light on flow and consider changing the water pump but again, it could be partially blocked

If they are the same temp, you can try to back flush the heater core as a stand-alone unit thus keeping track if any debris ends up in your catch basin.

If you have one of those laser temperature readers(they are quite cheap now ) this makes your job really easy.

Just measure the 2 heater hoses and coolant temp in the rad itself and those numbers will tell you if you have to flush your heater core or change your water pump or just burp it more thoroughly.


In the absence of a laser thermometer, I'd do the easy stuff first by re-burping the heater core
Throw a rag over the loose coupling so you don't spray anti-freeze all over and then start the truck and bring the rpm's up to 2500 and hold it for a few seconds (15-20) and watch for air escaping.
If the flow seems strong, & steady, tighten 'er up, check your reservoir, tighten your rad cap and try it out again.

Just a thought...did you change your rad cap when you changed rads? You might want to do that regardless.

If you are not in stop & go traffic, regular airflow through the rad should keep it cool enough with no fan so but it would be remiss to not inspect.

I did replace the radiator cap with OEM from the dealership with the radiator change out. I'm going to check the fan clutch in the morning just for the hell of it. Since I already have the part (whether it helps or not) I'm going to change out the T-stat which will cause me to re-burp the system.

If I'm still having trouble then I'm going to go through the process you suggested.

Does the dealership do the standard coolant flush in reverse cycle?

 

[Kurtis]

A thermostat does not instantly open/close at 180°. It will slightly open/close more and more depending on the temperature. The higher the temperature, the more it will open; allowing more flow. So, you will not see a difference in temperature when the thermostat opens and closes because it is designed to keep it at a certain temperature.

If the thermostat did open and close instantly you would have temperatures that fluctuate very rapidly which is terrible for metal on a long term scale.

If you see your temperature is fluctuating then it very likely that you thermostat is not operating correctly.

 

[robb1887]

Yes, replaceing the heater core in the dash was a PITA, but SOOOOOO worth it when I had heat again. Would do again 10/10. Would enjoy doing it 2/10, again.

 

[cj80cruiser]

Late reporting back but since my timing belt/water pump/thermostat change my temps have been 8-10* cooler and my heat has been nice and warm so far this fall. I believe my thermostat was sticking.

 

[4eigner]

Nice. I've actually referenced this thread last week with similar issues. I'm running a bit more hot on the hwy though. Oem Thermostat replacement seemed to help a little bit. But temps still climb on hwy to around 205-220 on the scangauge2; the more load, the hotter it gets. At idle it doesnt break 190 and around town it may occasionally break 200. Clog, water pump, or head gasket are on my mind.

Used a laser thermometer at the heater hoses and they get to about 160 at normal operating temps. When heat is blasting the return line drops to about 130. The heat currently blows between 100-110 in the cabin (hotter on the driver side vents). Does not feel as hot as it used to be. What's everyone else's blow at?

FYI: the needle will hover right in the middle of the temp gauge even at hot temps but shoots up to the red zone somewhere between 240-250 (at least on this vehicle.)

 

[tshandonay]

I'm having a similar issue on my 01 minus the high coolant temps. Drove 120 miles on the highway in the last couple days at the lowest temps we've seen so far this season. 15-25 degrees. Almost no heat at all out of the front....rear blows hot. Given the rear works and coolant temp on scangauge sits around 186 I think the cooling system is fine.

I did flush my heater core and burp air out in the summer, Temps on the in/out heater core hoses are similar. I'm fairly certain my blend door is working...I can see it move from the passenger footwell when I change temp from cool to hot.

Stumped....nothing really stands out as an issue to drill further down on.

 

[tshandonay]

I think I got some more air out of the heater core. Actually squeezed the hoses that go in and out of the heater core at the firewall to force air out. Even with incline it didn't produce any bubbled until I did this. Going to take a test drive now.

 

[piecesparts]

Anyone know what the dealerships do to get the heaters fully purged of air? I am experiencing a littloe warm air and not hot air when I have mine running and with the single digit cold, this morningi it was an experience I don't like.