Overheating-3 Weeks in 2 Shops Still No Cure

[CowboyBob]

I have a 2000 Limited with 127k on it. It has started to over heat while on Hwy(50+MPH). It will idle all day long and never overheat. Stop and go traffic and it does not overheat. I have to get it out on the Hwy and go about 50+ MPH, then after about 3-4 minutes, the temp gauge will rise rather quickly. If I pull over and stop the engine for 5 minutes, then start it back up, the temp gauge usually drops to normal almost as fast as it rose. This cycle repeats itself until the engine cools off.

One time when it did this I quickly pulled over and popped the hood and the reservoir bubbled for about 10 seconds then quit. It has never boiled over (come close to the top of reservoir but never over). It does not lose coolant. There is a smell of antifreeze, but I think it is spilled out due to all the work that has been done to it in the past 3 weeks.

It has been at 2 different shops and no one can figure out this mystery. Here is a list of parts replaced in order. Radiator was replace 16 months ago and is not clogged inside or out.

• Fan clutch
• Thermostat
• Radiator cap
• Water pump and timing belt (It was due for it so I had it changed)
• Second thermostat from Toyota

Here is a list of test that have been performed more than one time by 2 seperate shops.

• Leak Down test to 150psi all cylinders passed
• Compression test each cylinder
• Pressure test cooling system while running and not running
• Ran camera in each cylinder to see if anything bad.
• No steam cleaned spark plugs or steam cleaned cylinders
• No sign of coolant coming out of exhaust
• No water in oil
• No oil in water
• No white smoke
• Not hard to start
• No strawberry milkshake tranny fluid
• Never once thrown a code.
• No miss fires
• Does not leak coolant

I have looked through some old threads and saw that the rear heater hoses may be an issue. I have checked them and they look fine. I also noticed that there is oil leaking at the rear passenger side (looks like valve cover gasket). The valve cover gaskets where replaced about 4 months ago. Not sure if this is related to a head gasket issue or not.

I have been told that this is more than likely a head gasket or cracked block. And the head gasket or block is failing only when the cylinders have a load(high pressure in cylinder), which causes the exhaust gas to enter the cooling system. I have been told that the only thing left to do is pull the heads and take a look. I can pull the heads but don't want to do that and then find out it was something else that was simple to fix.

This has been very frustrating if anyone can shed some light on this issue I would greatly appreciate it.

 

[phattyduck]

Have you had the coolant tested for exhaust gasses? If there are no fluids mixing, no exhaust in the coolant, no clean spots on the pistons and no coolant loss, it isn't your head gasket.

Do you have a scan gauge or similar device that can read the actual coolant temp? That might help the diagnosis process.

The only thing left that I can think of - was the jiggle valve on the thermostat put in the right orientation? Its not the normal 12 o'clock position on the 5vz...

-Charlie

 

[shahsmerdis]

Hey! I welcome, finally got enough posts

which Radiator? If its autozone or anything other than denso koyo or oem i'd get another one. .

get a scan guage, take the radiator cap off, rev the engine until temps hit 90C+ to get all the air out of the radiator. make sure both rear and front coolers are all the way hot to open the heater core.

 

[pluton]

All I have is probably what you've already thought of:
Poor cooling at speed is classic clogged radiator. Barring that, poor circulation(water pump turned to dust inside, etc) of coolant...really, same effect as a clogged radiator. I once caused such a condition by mixing GM orange "death-cool" coolant with conventional green coolant.

 

[diverscale]

All I have is probably what you've already thought of:
Poor cooling at speed is classic clogged radiator. Barring that, poor circulation(water pump turned to dust inside, etc) of coolant...really, same effect as a clogged radiator. I once caused such a condition by mixing GM orange "death-cool" coolant with conventional green coolant.

GM death-cool hahah.

Ok, if we ignore the possibility of a cracked head and look for simpler things:

Well, it does seems to be a constrained air or water flow for sure, but you state that your waterpump was replaced in the trials to fix the problem, along with all the other elements that could come to my mind.

So you do have enough flow to cool the relatively low energy dissipation at idle, but once the engine produces lot of heat (highway), your system can't keep up.

Seriously, the only impossible thing that comes to my mind is that one of your hose is kinked. Next one is that your condenser is so dirty/clogged that it prevents the airflow to your radiator that is just behind.

If, when overheating happens, you turn on your heater to max heat/fan/oustside air, and the heat comes down, that could be a clue of what's going on.

 

[ellis36]

GM death-cool hahah.

Ok, if we ignore the possibility of a cracked head and look for simpler things:

Well, it does seems to be a constrained air or water flow for sure, but you state that your waterpump was replaced in the trials to fix the problem, along with all the other elements that could come to my mind.

So you do have enough flow to cool the relatively low energy dissipation at idle, but once the engine produces lot of heat (highway), your system can't keep up.

Seriously, the only impossible thing that comes to my mind is that one of your hose is kinked. Next one is that your condenser is so dirty/clogged that it prevents the airflow to your radiator that is just behind.

If, when overheating happens, you turn on your heater to max heat/fan/oustside air, and the heat comes down, that could be a clue of what's going on.

Replace both upper and lower radiator hoses. One has likely separated causing a blocking of the water flow.

ellis

 

[nissanh]

Are the parts you replaced are OEM or Branded like denso, Aisin or Koyo?
Fan clutch: Aisin ONLY
Radiator: Denso or Koyo ONLY

Like Diverscale mentioned, did you clean the AC condenser? (apply water to the ac condenser and radiator. Let is soak. Then from the fan side apply high pressure, a garden hose with a trigger will do. You are in TN and I am sure there are LOTs of bugs getting sucked in by the radiator fan. I used to live in Louisiana and every time I do a drive in the night, next day morning I see millions of bugs in the front-end.

Finally, Your radiator may be clogged or does not have the correct core thickness (OEM is 1 inch) most aftermarket are 1/2 inch to 3/4 inch

 

[mckennar]

I'll throw my hat into the ring on this one.

On my Subarus the space between the A/C condenser and radiator would clog up and prevent air flow at speed only and make it look like it was overheating. When I pulled the radiator (thinking it was a radiator issue) about 2lbs of debris fell to the floor that had sandwiched between the rad and A/C condenser.

On an old Honda I used to have, the condenser fins themselves one by one over time bent to the point at which it would restrict airflow and overheat on the highway. After a long, frustrating night of using a flat blade screwdriver to straighten the fins, the overheating problem went away.

Not saying these are your problems... but a good way to check is to do a smoke test - not a traditional "smoke test" but one that indicates whether or not air is flowing through the radiator/condenser sandwich.

Some people use incense wands for this, others use rolled up paper (I smoke a pipe, so I used that). Your smoke trail should look like this one (h/t to [MENTION=44220]BigFishAllDay[/MENTION]): http://i1360.photobucket.com/albums/r645/bfadalbumtres/BM 70268/7_zpsb5451517.jpg

Again, just a theory, and be careful with open flame around things that are flammable... like cars.

Good luck.

 

[IBallEngineer]

The tubes on aluminum radiators can swell to the point they impede airflow. Flushing of the cooling system can possibly show a problem with water flow, but that is difficult.

A good technician is what you really need.

This is not a 4runner problem, it is a finding a good tech problem.

 

[CowboyBob]

Ok update to some questions you guys have asked.

The last thing the mechanic told me he did was to clean between the radiator and condenser. I will go check and see just how well he did.

The thermostat was installed with valve in 12 o-clock(that is what mechanic told me), is this not correct?

The heat works even when the engine overheats.

I was told that the radiator was not clogged internally. I replaced it last year because it started leaking. It has had the red Toyota coolant in it ever since.

The parts are all aftermarket except for the Thermostat. I think the water pump is Denso.

I will check the ac condenser. The ac blows ice cold, so if it were clogged, i'd think that the air would be so cold. I'll check it anyway.

Will keep you guys updated.

 

[Southernbike]

I had the same problem years ago on a old mustang. Baffled me until I revved up the engine and watched the lower (I think) radiator hose collapse. I replaced it and solved the problem.

 

[CowboyBob]

I had the same problem years ago on a old mustang. Baffled me until I revved up the engine and watched the lower (I think) radiator hose collapse. I replaced it and solved the problem.

I will remember to check this the next time I get it to overheat. The radiator hose is only about a year old because I replaced the upper and lower the same time replaced the radiator.

 

[shahsmerdis]

Ok update to some questions you guys have asked.

The last thing the mechanic told me he did was to clean between the radiator and condenser. I will go check and see just how well he did.

The thermostat was installed with valve in 12 o-clock(that is what mechanic told me), is this not correct?

The heat works even when the engine overheats.

I was told that the radiator was not clogged internally. I replaced it last year because it started leaking. It has had the red Toyota coolant in it ever since.

The parts are all aftermarket except for the Thermostat. I think the water pump is Denso.

I will check the ac condenser. The ac blows ice cold, so if it were clogged, i'd think that the air would be so cold. I'll check it anyway.

Will keep you guys updated.

6 oclock apparently is the right position. but i doubt its going to prevent your overheating issue.

aftermarket is not the end of the world just what brand aftermarket. denso or koyo for radiator. anything else could be a problem

 

[kolelt]

I believe water pump is Aisin

 

[CowboyBob]

Ok here is an update.

I opened the hood and looked from the outside and could see the fan blade through the ac condenser and radiator. I blew it out anyway with a tool I made just for this purpose. It is an aluminum tube bent over at 90 degree angle at end. The water comes out so hard you have to hold it with two hands. I made it to blow all the chaff and grass seed out of my tractor radiator when I bale hay.

I let the car warm up to operating temperature and hooked up my scan tool so I could see exact temp. I then took it out for a long test drive at 55mph. The temp slowly rose about 1-2 degrees per mile. It hovered at 217 for the longest time, then started climbing again. It made it all the way up to 230, then I headed back home. The temp got up to 236 and when I turned in my driveway and stopped the car, it briefly jumped to 239 for about 10 second then gradually dropped over ten minutes (while idling in driveway) back to 199. I then turned off the motor. The whole time the temp gauge never moved. I drove it a total of 30 miles, the temp was about 15 degrees cooler outside from last time it overheated, so I think that is why I was able to go greater distance than last couple times. Also, the lower hose never collapsed or kinked.

I'm thinking maybe the fan clutch is no good. When I spin it with my hand as hard as I can spin it, it is not loose, but it will spin about 3 or 4 blades then stop. It never locks up all the way even when the motor was 239.

I'm also thinking about pulling the radiator and taking it to the radiator shop in town and having it tested. What do you guys think?

 

[diverscale]

fan clutch is not your problem as dynamic airflow should be enough at speed.

Did you try to turn on the heat in cabin while overheating?

If you turn on the heat to max, fan to max, outside air, and your temperature start to go back toward normal it might lead on to a restricted flow to the radiator for whatever reason.

 

[phattyduck]

Get the jiggle valve in the right position first... Guys on here report between 15-25*F too hot with it in the wrong position. Consider getting a new OEM thermostat while you are doing that labor.

If you don't get the big fan noise at startup, you probably also need a new fan clutch too.

-Charlie

 

[CowboyBob]

Get the jiggle valve in the right position first... Guys on here report between 15-25*F too hot with it in the wrong position. Consider getting a new OEM thermostat while you are doing that labor.

If you don't get the big fan noise at startup, you probably also need a new fan clutch too.

-Charlie

The thermostat in there now is OEM ($26 from Toyota dealer in town). I asked the mechanic and he said he put it in at 12 o'clock. I get the fan roar for about 5-10 seconds at a cold startup.

 

[ThorInc]

The thermostat in there now is OEM ($26 from Toyota dealer in town). I asked the mechanic and he said he put it in at 12 o'clock. I get the fan roar for about 5-10 seconds at a cold startup.

Service manual says 6 o'clock and it does make a difference to the temp readings but the original gauge won't register the difference. If they have to drain the rad have them flip it to 6 o'clock....and yeah they will argue it should logically be at 12 o'clock but not for this vehicle. However, this is definitely not your problem but they should fix it anyway. I have to go with a clogged rad but I got nothing else other than test the coolant for contamination?

 

[CowboyBob]

Service manual says 6 o'clock and it does make a difference to the temp readings but the original gauge won't register the difference. If they have to drain the rad have them flip it to 6 o'clock....and yeah they will argue it should logically be at 12 o'clock but not for this vehicle. However, this is definitely not your problem but they should fix it anyway. I have to go with a clogged rad but I got nothing else other than test the coolant for contamination?

How do you test coolant for contamination?