How Do I Replace a Thermostat on the V6?

[fdbyrne]

My thermostat is stuck open, apparently. A couple of days ago it started taking forever to warm up and not just because it's cold outside.

I need to replace the thermostat but can't find any writeups anywhere for the V6. Do you guys have any pointers? Do I have to drain the coolant completely to do it? I really hate to do that with the Toyota pink stuff being fresh and also quite expensive.

Any pointers would be greatly appreciated.

 

[Sherminator866]

I've haven't done one yet on the v6, but every other vehicle I've ever done is pretty simple. new thermostat/gasket and some basic tools is all you need. Get the thermostat housing off, scrape the surfaces if needed to get a good seal on the gasket and put it back together. A small amount of coolant will come out of the top hose, but not a ton.

-make sure to observe which way the thermostat came out, so you don't put it in the wrong way and it won't be able to open

** DO NOT over tighten the housing** They very easily can crack if not tightened carefully. Just take it easy and do both sides evenly and slowly, then apply pressure between the two sides until it's nice and tight. I've had many crack on me in the past.

Like I said, this is a broad approach from experience doing various vehicles and it might be a little different with the v6.

 

[fdbyrne]

Thanks. I appreciate it. I have a about a gallon of the recommended coolant sitting around to top things off with.

The FSM writeup for the V8 lists the first step as draining the coolant which had me concerned. I couldn't find the writeup for the V6 anywhere.

 

[MikeInNH]

The thermostat on the V6 is very simple to change. But you don't just replace the thermostat...you replace thermostat and housing. The come together as one piece.

2005 Toyota 4Runner Thermostats, Gaskets & Housings

No need to drain the fluid. A little fluid will come out when you disconnect thermostat housing.

This job should take no more the 20 minutes.

 

[Sherminator866]

I've never been concerned about losing a little bit of fluid then just topping it off, but it depends on if the 4runner is hooked to the bottom or top hose. If it is the bottom hose there should be a petcock on your radiator on the bottom and you can just drain down the radator and hoses. I see no reason to go through the trouble for a total system drain just to do the thermostat.

 

[fdbyrne]

This job should take no more the 20 minutes.

Famous last words. I think that every time I've said that it took me hours because of a rusted bolt or some other complication.

I appreciate the input guys.

 

[MikeInNH]

The hardest part is removing the hose. Usually because they get stuck on pretty good.

Then remove the 3 bolts holding the thermostat housing and the housing comes right off. The housing is right up front and easy to access.

 

[fdbyrne]

Just an update for anyone that might stumble across this thread months or years from now.

I just got done replacing the thermostat. By far the easiest thing that I've ever done to that truck. Don't hesitate to do it yourself. All you need is a 10mm socket to pull off the engine cover, a 10mm wrench (or better yet a ratchet wrench), a pair of channel lock pliers to compress and remove a clamp, and about half an hour of time. I lost about a pint of coolant which I promptly replaced when I was done.

It's right there in the front and on top. Easy to get to. Not much can go wrong.

 

[MikeInNH]

Excellant....

 

[bht2109]

Which gasket?

Hey guys! Thread revival here...


Just had a quick question about which gasket to choose for the thermostat replacement. On Rockauto there are 2 distinct shapes - triangle and circle - that are available. For example, Fel-Pro makes both styles, part#s 35767 and 35801 respectively.

To further add to my confusion, sometimes the word "seal" is used, and other times "gasket". AND I thought I saw a square-shaped gasket on some other site! Is there and inlet and outlet gasket involved in replacing the thermostat?

I know I'm probably overthinking this (for a $2 gasket? Yep.), but can you guys lemme know what I need? I should only need ONE gasket for the thermostat, right? For context, I'm replacing the rad, thermostat, and water pump as part of a 200k mile preventative maintenance schedule on a 2006 SR5 V6.

Going with the Aisin THT003 thermostat, by the way.

Thanks for you help!!!

 

[Supersonic]

I'd say get both, seems I only used the round one, but it also came with the thermostat.

What also doesn't get mentioned is you can't go straight on to the bolt(or nut) on the back, I'd recommend the 1/4" wobble extension, I didn't have one but managed.

 

[Miranthis]

Hey guys! Thread revival here...


Just had a quick question about which gasket to choose for the thermostat replacement. On Rockauto there are 2 distinct shapes - triangle and circle - that are available. For example, Fel-Pro makes both styles, part#s 35767 and 35801 respectively.

To further add to my confusion, sometimes the word "seal" is used, and other times "gasket". AND I thought I saw a square-shaped gasket on some other site! Is there and inlet and outlet gasket involved in replacing the thermostat?

[snip]

IIRC, from changing the t-stats in a few Camrys and a Sienna over the years, there is a gasket between the housing and he block and then a round seal that goes around the edge of the t-stat. So, if you have not already figured it out, I'll bet you need both the round 'seal' and the odd shaped gasket to do the full job.

 

[lightfreak]

Hey guys! Thread revival here...


Just had a quick question about which gasket to choose for the thermostat replacement. On Rockauto there are 2 distinct shapes - triangle and circle - that are available. For example, Fel-Pro makes both styles, part#s 35767 and 35801 respectively.

To further add to my confusion, sometimes the word "seal" is used, and other times "gasket". AND I thought I saw a square-shaped gasket on some other site! Is there and inlet and outlet gasket involved in replacing the thermostat?

I know I'm probably overthinking this (for a $2 gasket? Yep.), but can you guys lemme know what I need? I should only need ONE gasket for the thermostat, right? For context, I'm replacing the rad, thermostat, and water pump as part of a 200k mile preventative maintenance schedule on a 2006 SR5 V6.

Going with the Aisin THT003 thermostat, by the way.

Thanks for you help!!!

Aisin is the OE t-stat for the 4th gen, it should come with the seal you need.
I replaced mine after 300,000km and ordered from Toyota, it came complete with housing and round seal. It's all you need to do this job (besides coolant)

The triangular gasket is for the rear bypass joint of the cooling system. You don't need it, it's not part of the t-stat replacement.

The only thing I would caution is to not over toque the 3 bolts holding the t-stat. Since the housing is plastic it will crack.