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1998 Toyota 4runner overheating


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trmcph01
User

May 31, 2013, 4:23 PM

Post #1 of 12 (3927 views)
1998 Toyota 4runner overheating Sign In

1998 Toyota 4runner, 218k
The engine overheats and the fluid levels aren't low. There is a check engine light on but I haven't ben able to get a scan yet. I'm thinking it may be the thermostat or pump? Where should I start troubleshooting? Thanks in advance for any advice.


Discretesignals
Ultimate Carjunky / Moderator
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May 31, 2013, 4:26 PM

Post #2 of 12 (3926 views)
Re: 1998 Toyota 4runner overheating Sign In

Does it overheat at stops or while driving? Does the heater work?

Have you taken the cap off the radiator and checked the level in the radiator? What is the condition of the coolant?





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trmcph01
User

Jun 2, 2013, 10:04 AM

Post #3 of 12 (3863 views)
Re: 1998 Toyota 4runner overheating Sign In

The car overheats while driving and the heater does not work. Fluid was just replaced so it is fine.


Discretesignals
Ultimate Carjunky / Moderator
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Jun 2, 2013, 10:16 AM

Post #4 of 12 (3858 views)
Re: 1998 Toyota 4runner overheating Sign In

Faulty thermostat won't cause loss of heater performance.

Does the heater control valve function properly? Heater hoses hot?





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trmcph01
User

Jun 2, 2013, 12:08 PM

Post #5 of 12 (3850 views)
Re: 1998 Toyota 4runner overheating Sign In

The In hose with the valve is really hot, the out hose is not.


Discretesignals
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Jun 2, 2013, 12:14 PM

Post #6 of 12 (3849 views)
Re: 1998 Toyota 4runner overheating Sign In

You either have air in the system, the heater valve isn't functioning properly, or the core is plugged up.

Have you tried back flushing the core?





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trmcph01
User

Jun 2, 2013, 1:07 PM

Post #7 of 12 (3847 views)
Re: 1998 Toyota 4runner overheating Sign In

I just backflushed the core and it was fine, flowed easily with little water pressure. I took the valve off and it works. When I drained the radiator the coolant was not even warm.


Discretesignals
Ultimate Carjunky / Moderator
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Jun 2, 2013, 1:32 PM

Post #8 of 12 (3845 views)
Re: 1998 Toyota 4runner overheating Sign In

Normally even if the T stat was stuck closed and causing overheating, the heater would burn you out of the vehicle.

If you are sure you don't have air in the system, you could have a flow problem from a water pump issue. Water pumps are kind of hard to test. The pump on the 3.4L is driven off the T belt, so you kind of want to be correct in your diagnosis for suspecting a water pump issue if that is the engine your playing with.

There are no tools for testing water pumps, but you could make your own:

http://www.autospeed.com/..._110478/article.html





Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.


trmcph01
User

Jun 4, 2013, 10:40 AM

Post #9 of 12 (3823 views)
Re: 1998 Toyota 4runner overheating Sign In

I ended up back flushing the heater core, replacing the T-stat + gasket, and refilling the system. Everything seems to work just fine now. I'm not sure if it was the T-stat or air in the system but it is fixed and didn't have to spend a ton of money. Thanks for all of the help it is greatly appreciated.


trmcph01
User

Jun 4, 2013, 10:41 AM

Post #10 of 12 (3822 views)
Re: 1998 Toyota 4runner overheating Sign In

Just to help me learn something that I didn't understand. If the T-stat was stuck why would the heater burn you out of the vehicle? Seems to me that it would be the opposite because nothing is flowing through the core.


Tom Greenleaf
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Jun 4, 2013, 11:06 AM

Post #11 of 12 (3819 views)
Re: 1998 Toyota 4runner overheating Sign In

Dunno if DS is around right now but if a T-stat stuck shut, engine would get hot to total overheat and before it all boiled you would get super hot heater.

Hot air or plain air from being low will not transfer much heat - anywhere as liquid does,

T



Hammer Time
Ultimate Carjunky / Moderator
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Jun 4, 2013, 12:01 PM

Post #12 of 12 (3813 views)
Re: 1998 Toyota 4runner overheating Sign In

Coolant still circulates through the heater when the T-stat is closed. The only thing it controls is coolant into or out of the radiator.



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