Adding a thermostat bleed valve

[TurboRA28]

Hey all, got a question for you.. I have the biggest problem evah trying to bleed the coolant system in the 3sgte.

When I first installed engine had lots of problems, quick fix, drilled some holes in the thermostat which fixed the problem.

Problem is with that I find on cold days and light cruising the engine takes forever to get up to temp (15mins +) also it often just never gets there, will hang around 60 - 70 degrees.

So I recently purchased new thermostat and thought i'd give it another go with no holes in it. But after hours of trying to bleed it I gave up. The bottom hose just stays cold and engine eventually overheats.

I tried drilling just a very small hole 1.5mm in the new thermostat and it still didn't work.

Eventually gave up and put the old holey thermostat back in.

But would like to sort this problem out somehow.. I was thinking of drilling a hole in the thermostat housing, and tapping a bleed valve/screw in there to let air out when im filling the system up?

What is everyones opinion on that?

If its a good idea.. what side of the thermostat should I put the bleeder? The 3s thermostats are in the lower hose on the engine.

Thanks
Joel

[oldcorollas]

is it air that is the problem or just not enough hot water getting there to open it up?

when i put a decent gauge on the crappy K motor, the temp went ever so slowly up (like 2 minutes), and then when it reached opening temp, it would shoot up to about 5 deg above the thermostat opening temp.. and then suddenly go down again.. all in about 15 seconds.. and then the cycle would repeat itself...
to fix, i tried 2mm hjole but ended up with a 4mm hole in the thermostat, which kept the cycling down, but didn't affect the hot temp performance

if your temp gauge is responsive (i had VDO, and temp sensor was on hot side of the thermostat too..), then see if it cycles.. if so, try bigger holes until cycling decreases...
(if the gauge is not responsive... use a multimeter and measure the resistance of the sender....log every 5 seconds or so?)

are you sure it is air at the thermostat that is causing the issue?

if you drill hole in thrmostat.. do it at the egde of the side that sits highest (to let bubbles thru?)

tapping bleed in also sounds like good idea

but if you say engine stays cold until overheating, i'd be thinking about enlarging hole and logging cycling temps.. then going with smallest hole that keeps cycling down... once open, the hole makes little difference anyway.. and the thermostat should let water thru so that the whole system warms up quickly.. rather than shooting up and down..


or your cooling is too efficient

[TurboRA28]

Hey mate, thanks for that info.

I guess I cannot be sure if its air or not enough hot water getting there. I'll dig up a 3sgte coolant system diagram as there is a pipe from the block and also from the back of the head that feeds back into the water pump. So I would have thought this would provide the hot water.

The prob with enlarging the hole on the thermostat is it seems to dramatically increase warmup times. Also often after it warms up, a long gentle cruise and its down below operating temp. So I'm thinking too much coolant is getting through the hole in the thermostat?

I'll need to do some testing on that cycling. I did notice when I was trying to bleed it that it would get hot around 100 deg, the bottom hose still dead cold. Sometimes it would start to heat up the bottom hose so I figure the thermostat opened a bit, and temps would steady themselves around 100 and not keep increasing. But then the hose would go cold again and it'd start climbing up again over 100.

[jonra23]

Unlikely that you are getting air locks at bottom of cooling system, does the top radiator hose run up to the radiator or slope down with the 3s there.

Is the top hose getting warm at all, for the bottom hose to get warm requires a reasonable flow if radiator has decent airflow.

From your symptons i would be more inclined to think that thermostat is either too hot or temperature gauge is not quiet reading right.

[TurboRA28]

The radiator is higher than the engine, so the top radiator hose goes up.

The top hose is getting very hot, its the bottom hose that is staying cold. The radiator core itself seems to stay cold also.

The thermostat opens at 82 deg. I'm looking at the temp gauge and also the autronic temp sensor, both seeing similar temps.

[roadsailing]

have you tried un-doing the thermoswitch for the thermofan? that is sometimes designed as an air bleed.

actually, here is an idea, fill the radiator up with boiled water, if you have enough kettles

[Pure_In_Sanity]

Hey Joel
If it turns out air locks are the problem, it may be worth getting one of those small header tanks. They advertise them at the importers in magazines like Zoom.
That way you can run a few small bleed hoses from the head, thermostat housing, radiator hoses etc and mount it up high in the engine bay.
May look a bit messy, but its just a thought.

Cheers
-Phil

[jonra23]

Where are the temp sensors in relation to thermostat housing?

Not familair with 3sgtes, so sorry if not on track.

The only systems that i have played with that have thermostat in bottom hose have a small (19mm or so) hose that runs from top raidator hose back into the thermostat housing, this circulates coolant continualy and the theromstat only bleeds in cool water from radiator to balance water temp going into motor.

Because of this there is a only a small flow through radiator unless motor is under a reasonable load and it is not unusual for bottom radiator hose to feel fairly cool.

If the thermostat is 82 degrees it is only going to take a very small amount of cool water from bottom of radiator to dilute the hot water circulating inside engine back down to closing temp again, unlike a discharge thermostat type system that will bring a engine block amount of cool water into engine.

[30psi 4agte]

is the water pump ok?

it does sound like a thermostat prob though providing the temp gauge is accurate.

[TurboRA28]

Shinybluesteel - ha that suggestion of boiling water was actually something a mechanic said to be. But yeah, not sure how practical that would be. I guess i'm trying to find a fix that means future coolant changes are not always going to be a headache.

jonra23 - Due to the nature of the rwd 3s conversion, the thermoswitch and temp sensor are in a pipe about 15cm away from the outlet at back of head that runs from the rear of the head back to the top radiator hose. That is similar to factory, just in factory they are actually in a housing that comes off the back of the head.

There is also a pipe from the outlet at the back of the head (small 19mm thing) that runs back to the water pump.

Phil - good idea mate about the header tank! I will research that a bit more.

[TurboRA28]

Oh yeah, forgot to mention.. Brand new water pump.. It all seems to do what it should with a few 6mm holes in the thermostat, temps stay in check even on track days. But then I might as well not have a thermostat.

[kingmick]

You still need the restriction in the water way
Unusual problem, You might want to go a higher temp thermostat and give it a go. There cheap so its an easy test!

[jonra23]

An air lock in the 19mm hose possibly?, can any ait trapped in it work its way up to top tank of radiator?

Does it overheat under load or just when idling?

regards
jon

[TurboRA28]

Thats possible Jon.. Air probably couldn't get out of that hose very easily.

Overheats just at idle, don't need to load it up.

I'm thinking one of these external header tanks might be the go? Could run a few hoses into it from areas air might get stuck, like the 19mm hose from back of head to water pump, maybe the thermostat area itself?

[allencr]

Due to the nature of the rwd 3s conversion,

OK, now we know that this is something cobbled together!!!!!
I think you've got your piping wrong.
Every engine that isn't being raced at its max needs a thermostat, and every thermostat needs water to circulate by its bulb/sensor to operate when needed. A small hole or notch may be needed in the thermostat for air to purge easily.
It's pretty difficult to have an 'air lock' when anything over 2500rpms will
produce lots of pressure & volume from any water pump.