The curious case of the over-heating radiator — that doesn't over-heat

[StreetCreeper]

When driving or sitting still, I have never seen the temp gauge move once it has reached normal operating temperature. However, I have on occasion smelt coolant while idling in a drive-thru or whatever, and on occasion, I've also noticed coolant that had leaked out of the overflow reservoir after parking...usually after having smelled coolant.

Mind you that this is with the air conditioning on. While driving, the A/C stays around 42 deg. But within 4 or 5 minutes of idling in park or neutral, the A/C temp will climb to around 60 deg (and probably higher but I shut it off).

My first thought was the fan clutch, but the fan seems to have decent resistance when I spin it, so I'm guessing it's not slipping.

So now I'm thinking maybe it's the radiator cap not holding the pressure and just lowering the boiling point? This (at least in my noob mind) would possibly jive with why I'm not seeing the temp gauge increase even though I am pushing a little coolant out of the reservoir.

I'm planing to replace the radiator, radiator cap, upper & lower hose and thermostat in about a week— just as preventive maintenance as I've not noticed anything wrong with them at all.

So I'm curious what you all think? Old radiator, fan clutch, radiator cap....or other?

 

[LittleCaesar]

I'd start with the cap and go from there. OEM for sure. I'd do a cursory check for bubbles in the coolant as well.

I usually give fan clutches 15 years or 150,000 miles. Past that and who knows. Check for play in its bearing when you have it off.

 

[cashmoney]

Could also be a bad coolant temp sensor.

 

[StreetCreeper]

I'd start with the cap and go from there. OEM for sure. I'd do a cursory check for bubbles in the coolant as well.

I usually give fan clutches 15 years or 150,000 miles. Past that and who knows. Check for play in its bearing when you have it off.

Could also be a bad coolant temp sensor.

So I was going to replace the radiator cap today with an OEM one from the dealer, but on principle, I'm not willing to pay $22...which is like $8 over MSRP, and I'm not going to waste money on a cheap parts-store one either. So I'll order it with other stuff online.

While looking up the part number for the cap however, I noticed on the parts diagram that the overflow reservoir cap assembly has what appears to be a hose extension that connects to the cap and sits deep inside the reservoir. I don't see this on mine.





So now I'm thinking that the coolant gets pushed into the reservoir when hot but doesn't get sucked back into the radiator when cold because of the lack of hose. Then I unknowingly topped off the radiator when I checked it before a recent trip—which essentially added too much coolant to the system and subsequently created a condition where the excess hot coolant was forced out of the reservoir later.

This would explain why I wasn't seeing an increase in coolant temp on the gauge even though I was leaking a little coolant from the overflow...but it doesn't explain the A/C temp increasing 20 deg while stationary.

Though to be honest, I don't know if that is abnormal or a symptom of another A/C related issue. The refrigerant level/pressure was correct when I checked it about a month ago. I eye-balled the A/C condensor and while I didn't see any obstructions, it does look like it's been around for a long while. Could an old inefficient condensor explain the quick A/C temp rise while stationary?

I think I will wait until the coolant is cool again, then pull the reservoir and empty it to see if there is a piece of hose at the bottom and go from there.

Also, I contacted the PO and they advised that they had replaced the radiator and thermostat about a year ago. So I will not be replacing those for preventive maintenance after all. But I will be flushing the green coolant out and putting in the proper red.

I'm hoping I don't have to mess with the coolant sensors as I understand the rear one can be a PITA, but I will cross that bridge when/if I get there.

 

[cek77]

Just went through my cooling system, it's fresh on my mind. On the reservoir cap there is a rubber hose that reaches to the bottom of the tank. Yours may have fallen in? Pull the whole tank straight up and it comes out. No mechanical connection. Pull it out and clean the crud out of the bottom. See if hose fell in. It's big so it should be easy to see.

Since your draining the antifreeze I'd go ahead and check the thermostat. Make sure it's a toyota. So easy to change out or at least check. 3 12mm nuts.

When your AC is on what is your idle speed? I just noticed mine is up over 1k when AC is on.

 

[StreetCreeper]

Just went through my cooling system, it's fresh on my mind. On the reservoir cap there is a rubber hose that reaches to the bottom of the tank. Yours may have fallen in? Pull the whole tank straight up and it comes out. No mechanical connection. Pull it out and clean the crud out of the bottom. See if hose fell in. It's big so it should be easy to see.

Since your draining the antifreeze I'd go ahead and check the thermostat. Make sure it's a toyota. So easy to change out or at least check. 3 12mm nuts.

When your AC is on what is your idle speed? I just noticed mine is up over 1k when AC is on.

So I pulled the reservoir and wouldn't you know it—the rest of the hose was wedged down in there...along with a white plastic "thingy" that I presume is supposed to not let the hose fall in there to begin with.



Anyways, got it out and re-attached after getting the reservoir cleaned out. It had been filled to the top with coolant and I was able to pour about half of it back into the radiator. I then ran the engine with the cap off until it was at normal operating temp, but it didn't take anymore.

Filled the reservoir up to the full mark and took it for a drive. The outside air temp was an even 100 degrees and the A/C was blowing at 45 deg while driving.

I then stopped and put it park and watched the gauges while idling. At the 5 minute mark, the A/C was blowing at 50 degrees.



At 10 minutes idling in 100 degree heat, no change in temp gauge and the A/C was blowing at 52 degrees. No coolant smell and no leaky reservoir.



I guess that was the problem—the reservoir hose.

Case solved...

Oh and when my A/C is on, the idle kicks up to about 850 or so.

 

[absalom]

Very satisfying indeed. Now for your next case ...

 

[crozhuyou]

I'd do a cursory check for bubbles in the coolant as well.

 

[StreetCreeper]

I'd do a cursory check for bubbles in the coolant as well.

I stood and watched the coolant in the radiator from cold startup until normal operating temp was reached and thankfully didn't see any bubbles.

 

[LittleCaesar]

It is always the little things.

Where did you go to get the Gearwrenches replaced in the end?

 

[StreetCreeper]

It is always the little things.

Where did you go to get the Gearwrenches replaced in the end?

I'm a procrastinator, but I'm going stop being one—starting tomorrow...

I have just been babying it. I only break things loose with the open end of that wrench, and then gently use the ratcheting end. So far it's worked, but I expect it to crap out at some point if I don't swap it out soon.