Had timing belt done at dealer, now runs hot...

My first guess is that they replaced the thermostat and put the valve in the 12 o'clock position. I'm going to drain it and check tonight.

I dropped it off and it was running at 193 per usual. Picked it up and was running 200-202 on the freeway. Touched 204 on side streets.

Everything else looks good under the hood. New belts, pulleys, tensioner, thermostat, cam seals front seal.

Side note, I wrote Haynes and asked about the position they say the jiggle valve needs to be in (12 o'clock) and sent them the .pdf from the 03 FSM as a reference. Asked if they had a mistake in their manual...

We'll see what they say. Did it out of curiosity.

Copy of email:

My name is:

Jim Johnson

My Haynes manual is:

Toyota Tacoma 1995-2004, 4Runner 1996-2002, T100 1993-1998

My question or comment:

Regarding the jiggle valve position for a thermostat replacement on the 3.4 V6. The Toyota Factory service manual states that the jiggle valve should be “downward”. I’m guessing at the 6 o’clock position. Your manual states that it should be within 15 degrees of 12 o’clock. I replaced the thermostat on my one owner 04 Tacoma and found it to be near the 6 o’clock position.

There is a debate on a Tacoma forum regarding this, and some have done comparisons to coolant temp with the valve in both positions using a scan tool to monitor engine temp. With some noting higher temps (5-15 degrees) while in the 12 o’clock position and lower in the 6 o’clock. (Nothing you should be concerned about really, just us forum guys being picky.) But I have included a PDF of the 03 FSM to show that it does indeed state that the valve should be installed in the 6 o’clock position.

So is there an error in the Haynes manual with regard to the actual position of the jiggle valve?

Thanks for your time,

 

Yep sounds like the thermostat. I too went to the Haynes and had the same problem. Looked it up here and changed it around. Fixed. Haynes is wrong.

 

Convention is having the jiggle pin at the top, since that's where the trapped air usually is. Must be something unique with the 5VZ waterpump/ thermostat housing design.

 

Yeah, I'm just curious if the dealer got it wrong. I won't be surprised if they did. But I will wonder why.

Also curious what Haynes says.

I'll be checking it tomorrow morning.

 

Probly just something that was overlooked. It happens. Just drain your coolant into a clean container, check the thermostat and turn if need be, refill, done. I probably wouldn't have gone through all the hassle unless it turns out to be installed correctly. Not raggin on ya, just sayin At least it wasn't something major or pure ignorance on Toyota's end. Then I'd have something to say.

 

No, I know you're not raggin on me. Honestly I'm not even upset in the slightest, just kind of proud that after all these years on here, that I wasn't 3 minutes down the road and already had a clue what it could be. I just got used to seeing my temps at a certain threshold and want it back where it was.

It is a very easy fix, in fact the thermostat wasn't even a few years old as I had replaced it and the hoses a while back. But hey, they had it apart and I had a new one in an "Aircabinman" kit from eBay.

No, I'm very happy with the service I had. I don't go to dealers often, but I have confidence everything was done correctly. There are yellow paint pen marks on all the bolts they removed (comforting), and got an honest assessment about my valve cover gaskets. It's about what I thought.

 

You can't expect mechanics to do everything right. They only charge $100/hour.

 

Out of curiosity why would they mark bolts and hoses?

 

Probably for a visual reference that the bolt has been torqued. If you look at some new cars, a lot of the bolts will have some sort of blue red or yellow paint on them. Maybe they have a second tech check the work and look for all the necessary marks. That's my best guess.

 

So the answer is yes, the tech placed the jiggle valve in the up position...

The picture with the temp reading 204 is on the way home from the dealer (plus a few photos of the thermostat) and the temp at 191 is after I switched it this morning.

You can see some of the yellow paint mentioned above...

 

Awesome man, good to hear the fix wasn't a tough one. But it sucks not being able to trust the people you take it to to get fixed or maintained!

 

It's crazy that something so little, would make such a difference.

I run 204 - 211 Engine Temp via SG2, and I assume when the TB / WP was done the technician made the same mistake 40,000 miles ago. Everything has been operational and fine, but makes me wonder if I should do the same...

 

Yes, you definitely should at least check it to make sure the thermostat is positioned correctly. If it's not, correct it. If it is, figure out why your truck is running so hot. You've been running 40k miles, probably daily, about 30-40 degrees higher than your engine is supposed to run. For your own good, I'd recommend correcting it as soon as possible, like yesterday.

 

Point taken. I purchased the truck back in January (10,000 miles ago) and hadn't given it much thought or concern really. With that said, how easy is it to check? Not the most mechanically sounds, but do have some conventional sockets / wrenches. It looks like i'd have to drain the coolant...

 

You in a V6 or I4?

 

3.4L V6.

 

Either way it's going to be pretty easy to check where that jiggle valve is setting. I wish I had some pics, you know what, I'll bet there are some threads here that have good pics to guide you. I'll try and find one.

Edit: BTW, I'm jealous of your TRD double cab, you and all the other butt monkeys that have them.... Why can't I have one and you can??? Lol, nice truck. They are very nice, I like them.

 

Well couldn't find one, lol. I'm in a 2.7 four cylinder, but I'm sure it's very similar... Wait a minute there's gotta be something in the sticky section at beginning of the recent threads. Check there. Find your lower radiator hose. Follow it from the radiator to the engine. Where it connects to the engine is the thermostat housing. I wouldn't drain the coolant, but you will lose some coolant when you remove that lower hose from the thermostat housing. There are 2 or 3 bolts holding the thermostat housing cover down. Remove them. It's likely the housing will not come off by hand when the bolts are removed. You'll need to break it free by hitting a piece of wood (2x4,etc)with a hammer or something as it the wood or whatever you use is resting against that thermo housing. Get that off and you'll see the thermo sitting there still in the engine. Look at where the jiggle valve is oriented. If it's at the 12 o'clock, remove the thermostat (you'll lose a lil bit more coolant when you remove the thermostat, just don't be alarmed) orient it correctly and reinstall. The gasket that goes around the thermostat is likely fine with only 40k miles on it. And just read those instructions in reverse to put everything back, lol

 

Dude, it really is a complete mystery to me why this happens. I mean, some say it's for air to pass by. I don't know how this valve opens and closes but it has to be a very tiny amount of fluid that passes through. Whatever reason it's a 10-12 degree difference in my truck. Lol

I usually run 193 all day long. Now 191 seems to be the new normal (new water pump?). The thermostat is way easy. Draining the coolant was what took the most time.

Drain coolant

Remove the three bolts in the thermostat housing. A 3/8 12mm deep works best for all three. They are torqued to 14 ft lbs.

If the valve is at 12 o'clock, place a container under ththermostat, because when you pull it to flip it, more coolant will come out.

Put it all together and fill up the radiator. Give the top hose a squeeze to get the air out with the engine running.

Enjoy cooler temps?

 

I got a reply from Haynes:

Hello Jim,

This is an interesting 'live data' design question. The engine thermostat would first, have to be tested for the exact correct temperature rating and operational dynamics before running this test. Then, of course, the exact same thermostat must be used for the number 1 position and number 2 position of the jiggle valve. The scan tool temperatures would have to be compared to an infra red temp tester as well. Thanks for the feedback and our department will certainly look into this situation.

Technical Research Department - Rob