MarkT

Just finished up my Timing Belt/Water Pump/Thermostat/etc; and noticed (after the fact) that my FSM says the Thermostat should be installed with the Jiggle Valve in the lowest (6 O-Clock) position. I did not pay any attention to which way it was pointing when I installed it. Just for the heck of it I also checked my Haynes Manual; it says the Jiggle Valve should be installed in the highest (12 O-Clock) Position.

Does anyone know what the function is of the Jiggle valve; why it matters what position it is in when the Thermostat is installed; and which is the proper position; when installed; the FSM or Haynes??

Thanks;

Mark

SEAIRESCUE

The valve allows trapped air to escape when the cooling system is flushed or broken open and drained. The trapped air is a serious problem creating hot spots and eratic sensor behavior. There are reports that the air is hard to remove without the valve. Since air seeks vertical height in water, I would be comfortable with the valve at 12 o'clock but I personally don't think it matters.

My$0.02

MTL_4runner

I've seen it installed both ways (12:00 and 6:00) and neither seems to affect the operation of the vehicle or the cooling system. That being said I always install mine at the 12:00 position or close to it.

MarkT

Thanks; I'm going to drain the system and re-install the new T-Stat with the valve at 12:00.

What got me wondering about the whole thermostat thing; is I reached down to feel the lower hose a couple times after the engine was at normal operating temp (about 1/2 way up on the dash temp gauge); and the hose is always cool. I've driven about 50 miles on the new Thermostat; no other signs of running hot. I'm wondering if my new thermostat (toyota brand) is functioning. Going to test it tomorrow in a pot of heated water.

Mark

warriors_03

That hose should be cooler...as its at the bottom of the radiator where the coolest coolant is. Also, did you check it after it had been driven and was at temp for a while? The gauge may show that it is at temp, but that the internal temp of the engine, and the coolant in the radiator may have not been heated completely yet. It takes more time for the entire cooling system to reach temp as well.

toytech76

I always put mine at 12 oclock as well. Some people cut them off when they want their motor to run a little cooler. (dumb) After you put it all back together and run it, let it sit and get cold then just recheck your levels and top off as needed. After that you should be good

MTL_4runner

Mark, that is totally normal (esp in winter.....the lower hose may actually stay cold).
I'd say unless you are overheating, your system is functioning properly.

MarkT

I've checked the lower hose after quite a bit of mixed driving (City/Interstate); no signs of running hot at all; but it still stays cool to touch. It has been cold here since I did the work on it last week; highs in the +10 to +20F degree range; lows down to -10F at night. If the cool lower hose is normal under these conditions; I guess the only reason to reinstall the T-stat is to re-position the Jiggle Valve; right now I have no idea which position it is in.

Thanks;

Mark

warriors_03

With those temps, I would put an educated guess that the lower hose is loosing any heat that it has on it from the difference in temps. What matters is that the gauge is reading normal, and saying that the heat in the cabin is pumping out good and hot air when fully warmed and full heat, then you should be good.