Mystery overheating

[MichaelRS]

I have a 2002 Toyota Sienna that currently has 242k on it. For about 2 years now I've had a mystery overheating problem.

I could be driving down city streets or the freway with or without the air conditioning on and sometimes it will start to overheat and sometimes it won't. To counter that I have to turn on the interior heating at full blast and the temperature starts to go down.

The only one pattern I've noticed is that many times after driving on the freeway and coming off it will start to overheat maybe 70% of the time.

Although recently I think that over heating has been too hard on my hoses because I've sprung a leak from one of the houses that comes out under the center of the engine on the passenger side and I think there's another leak down below. The leak(s) are so bad that it doesn't retain any coolant for more than a minute.
My mechanic has to take off the upper intake in order to get to all the stuff back down behind it but I'm not able to have that done until 4 days from now.

And, short of just starting to replace parts, he's not sure of why it might be overheating in the first place and that's why I haven't had the issue corrected in all this time.
That and my only income is my Social Security so there's not a lot of discretionary funds available and why i'm driving around in a 23-year-old car.

So, based on the vague symptoms that I have described, does anyone have any idea as to what the base overheating issue might be?

 

[bdcardinal]

Do you hear the fan turning on?

 

[dishdude]

It sounds like you might have a bad headgasket that's letting compression gases into the cooling system.

 

[MichaelRS]

Do you hear the fan turning on?

I can't swear that it's turning on all the time at the proper times, but it does turn on. So it's seems to be one of those things kind of like a watched pot doesn't boil while you're looking at it. And it also comes on when I turn on the AC

 

[MichaelRS]

It sounds like you might have a bad headgasket that's letting compression gases into the cooling system.

Ugh. That would not be good $$ wise. But wouldn't I see some contamination in the oil, that cloudy milkshake appearance?
Or could the leak from the gasket be so slight that it's only one way letting hot gases out?

 

[Rand]

clogged radiator?

if turning the heat on high helps.. its not shedding heat from the radiator properly for some reason. (fan, clog, thermostat, bug guts buildup on fins etc)

 

[Boomer]

Some ideas to check:

1. Check the fins on the radiator for debris that might be hindering air flow.
2. Water pump vanes may be bad and not always pumping correctly.
3. You may have an air bubble in the system.
4. Lower radiator hose maybe collapsing.

 

[MichaelRS]

clogged radiator?

if turning the heat on high helps.. its not shedding heat from the radiator properly for some reason. (fan, clog, thermostat, bug guts buildup on fins etc)

Could be, but SHOULD not be. I forgot to mention that I replace the radiator with a brand new one a year ago and the problem stopped for a bit but then started up again. But yeah, some of the other stuff. <sigh>

 

[Exhaustgases]

And no mention of the thermostat ? I remember many years ago traveling with my dad and having a weird transient over heat in his Datsun pickup. Only happened once and never again. So strange.

 

[Brian123]

Although recently I think that over heating has been too hard on my hoses because I've sprung a leak from one of the houses that comes out under the center of the engine on the passenger side and I think there's another leak down below. The leak(s) are so bad that it doesn't retain any coolant for more than a minute.

Did you correct the Coolant Leak?

The leak(s) are so bad that it doesn't retain any coolant for more than a minute.

I did not see this 1, so this car loses all coolant in 1 minute, where is it going, it has to be leaking somewhere?

And, short of just starting to replace parts, he's not sure of why it might be overheating in the first place and that's why I haven't had the issue corrected in all this time.

Wow!

 

[MichaelRS]

Did you correct the Coolant Leak?

I did not see this 1, so this car loses all coolant in 1 minute, where is it going, it has to be leaking somewhere?

Wow!

No. I don't have the money for my guy to get in there and do anything until 4 days from now.

When the coolant leaks out it just pours out the bottom. Right now I'm using water and when I pour in a gallon it just leaks out somewhere in the back/bottom at about half the rate of which pouring it in. So pretty quickly.

As I mentioned there's one visible leak in the hose that transverses the Middle top of the engine but I don't know if it's all leaking out there and I can't see the leak from the underside of that particular hose or if there's an additional hose leaking somewhere else.

As is every 4 hours or so I just turn the car on for about a minute, because I do have to move it a bit, and to keep the battery up.

 

[mk378]

You need to stop driving it while there is a major leak.

 

[Japanese]

There is no mystery overheating, you need to replace your water pump and timing belt as well when you are down there. I have a friend with Sienna and his overheating went away after he replaced the water pump.
Do you have an idea when was the last time the timing belt and water pump were replaced?

Try to don't drive the car until you do that. Make sure you keep adding coolant, so you don't go below min. in the expansion tank an the radiator should be full at all times.

Don't use water instead of cooland because you will cause even bigger damage to your engine

 

[The Critic]

Although recently I think that over heating has been too hard on my hoses because I've sprung a leak from one of the houses that comes out under the center of the engine on the passenger side and I think there's another leak down below. The leak(s) are so bad that it doesn't retain any coolant for more than a minute.
My mechanic has to take off the upper intake in order to get to all the stuff back down behind it but I'm not able to have that done until 4 days from now.

Sounds like the valley plate is leaking, which requires removal of both the upper and lower intake manifolds. The center bypass hose is also leaking. If you're going that deep, you should at least consider replacing the knock sensor sub harness, possibly even both knock sensors if budget permits.

 

[ecotourist]

I had something similar with my Volvo. When the weather was very hot, the engine would get quite hot (according to the temp gauge, it never boiled over) when I came off a fast run on the freeway.

I had the radiator cleaned inside and outside at a radiator repair shop and it never happened again. There was a lot of junk both inside and outside.

Do you have electric radiator fans? Are they working? I would also wonder about the thermostat and the water pump.

 

[MichaelRS]

There is no mystery overheating, you need to replace your water pump and timing belt as well when you are down there. I have a friend with Sienna and his overheating went away after he replaced the water pump.
Do you have an idea when was the last time the timing belt and water pump were replaced?

Try to don't drive the car until you do that. Make sure you keep adding coolant, so you don't go below min. in the expansion tank an the radiator should be full at all times.

Don't use water instead of cooland because you will cause even bigger damage to your engine

I know and all your advice is spot on, but unfortunately I have no choice. So fingers crossed.
Timing belt and water pump 81k ago in 2015. At least I keep good record <sigh>

 

[jjblbi]

Have you checked any Toyota or Sienna owners' forums? This overheating problem may have been diagnosed and/or remedied there. Good luck, John

 

[meep]

1. Is it holding coolant?

2. Is it holding pressure at op temp?

3. Do the cooling fans come on once it’s fully warmed up?

4. Does the upper cooling hose go from warm to HOT when the T-stat opens?

5. Is the water pump moving fluid?

6. Is the coolant clean to the appearance or is it nasty?

 

[jjblbi]

I had another thought...could coolant types have been mixed at some point and caused a "sludging" condition in your cooling system? Once your leak is sorted you might want to try a coolant system flush. Do some research, Cascade may be an option.

 

[Mechanician]

I've seen water pump impellers cause similar problems as well. Seen both rotted away metal ones, and slipping plastic ones.
Otherwise I would suspect an air flow problem - not enough through the radiator for some reason.
An electric fan should run whenever the A/C compressor is on.