thermostat won't open

[speedfreak]

right now i could let my car idle all day and it won't open the t-stat it's definitely not stuck i've taken it out twice now for testing and it opens at the specified 180f its also fairly new. my 7mgte has a totally stock cooling system except for a nice fat alum radiator and i cut the jiggle valve out of the t-stat, oh and i have no fan shroud. ive tried rallying it up a thousand foot climb and city driving still i dont think its getting hot enough to open which is fine in reality but ive had too many overheating issues in my life to feel comfortable with this. is idleing not the best way to get the t-stat to open? could my unshrouded fan be cooling the housing? could enough coolant go through the jiggle valve hole to keep the car cool? impossible! help me! oh i almost forgot to mention i have a meat thermometer stuck in my upper rad. hose to check temps after the t-stat and when i shut the car off after a run without opening the t-stat it seems to finally open and my thermometer climbs slowly to 180f but the lines arent pressureized for obvious reasons, this is kinda a dumb post but i need some peace of mind, thanks all.

 

[Kevin]

how do you know your tstat isnt opening?
is your car overheating?

 

[TurboStreetCar]

how do you know your tstat isnt opening?
is your car overheating?

:word8kn:

 

[speedfreak]

no its not overheating at all i can drive to the top of a hill and open the radiator cap no problem, also i can tell cause the upper rad. hose never gets firm after driving or idleing

 

[Kevin]

if your not overheating, your tstat is opening..
also.. what do you mean by "firm" how do you measure "firm" does it feel the same as a totally cool engine? or is it a little firmer? but not firm enough? lol

 

[lewis15498]

Are you sure you cooling system is full and has no air in it?

 

[speedfreak]

by firm i mean hard as hell when the thermostat is open the once squishable radiator hose becomes hard as a rock also if the radiator cap is off when the t-stat opens shouldnt the coolant come bursting out?

 

[Kevin]

so wait.. why are you checking anyway? is there anything wrong with your car?
did you once squeeze the hose and it was hard as a rock in the past and then modified something and re-squeezed it to check? lol im confused.. if there's nothing wrong with your car.. its not overheating.. why so paranoid?

 

[speedfreak]

uh cause i just dumped a year of my time and like $3000 bucks into it, im just worried that the tstat is not opening for some reason and the coolant inside the engine is reaching a critical temp and its hard to trust the temp gauge

---------- Post added at 09:29 AM ---------- Previous post was at 09:27 AM ----------

ya im pretty sure there is no air in it lewis theres no heater core gurgleing or obvious air pockets anyway

 

[Moy]

How much power are you making (mod list)? Also how is your gas mileage and air-fuel ratio (if you have a wideband)?

It sounds to me like you aren't reaching the optimal operating temperature that the ECT tells the ECU to go into closed loop. Your radiator sounds to be oversized for your application, resulting in too much cooling and lower coolant temperatures

 

[speedfreak]

ah thank you moy yes my 7mgte has eagle rods with probe pistons .020" over, a cometic mhg, and a 57trim ct-26, drilled out jtube, and a shimmed oil pump, thats about it for now as i have a stand alone system ill be adding later but right now its basically stock, no wideband yet, but the radiator is pretty big and has a 16psi cap

 

[Moy]

ah thank you moy yes my 7mgte has eagle rods with probe pistons .020" over, a cometic mhg, and a 57trim ct-26, drilled out jtube, and a shimmed oil pump, thats about it for now as i have a stand alone system ill be adding later but right now its basically stock, no wideband yet, but the radiator is pretty big and has a 16psi cap

Stock system pressure is supposed to be just below 1 bar pressure, around the 13.x psi area, with the pressure relief valve on the cap opening at 14.9 psi. Your cap is also overrated for the system.

If it were my car, I'd personally buy a stock pressure radiator cap, which will let the coolant reach a higher temperature.

 

[speedfreak]

thanks moy thats good input

 

[Moy]

not a problem

 

[TurboStreetCar]

The firm-ness of the radiator hose has to do with pressure, nothing to do with if the thermostat is open or not. If the thermostat wasn't opening and the system was overheating then the hose would be very firm as it contains the boiling water.

Use a stock radiator cap because if the pressure gets higher then stock it may stress things in ways they weren't designed like the heater core and heater hoses.

What does the coolant temperature gauge read when you are driving the car?

Because the hose isnt "firm" does not mean the car isnt reaching operating temperature. My car will operate at 180-190 without having really firm hoses. That temperature is reported to me by my standalone with the sender in the engine side of the thermostat housing.

Pressure in the system is regulated by the radiator cap, pressure in the system is to keep the water from boiling. Not much pressure is required as the coolant (even using straight water) shouldn't boil under normal operating conditions. Normally the only pressure generated is the expansion of the coolant when heated being contained by the radiator cap.

If your temps are good on the stock gauge and you dont trust it grab an after market gauge and recheck. I wouldn't worry because the hose isnt hard.

MOY: A higher pressure cap only increases the boiling point. Changing the cap wont change the temperature of the coolant.

 

[Moy]

MOY: A higher pressure cap only increases the boiling point. Changing the cap wont change the temperature of the coolant.

Ah yes, you are correct about that. I apologize for the misinformation. I just consulted my textbook and it says the same thing.

 

[jdub]

How much power are you making (mod list)? Also how is your gas mileage and air-fuel ratio (if you have a wideband)?

It sounds to me like you aren't reaching the optimal operating temperature that the ECT tells the ECU to go into closed loop. Your radiator sounds to be oversized for your application, resulting in too much cooling and lower coolant temperatures

QFT. What kind of radiator? What coolant are you running and in what ratio to water?

You might be getting enough flow through the jiggle valve hole...did you enlarge it? What brand of T-stat? Or, your T-stat could easily be just cracking open allowing flow to the rad - a big radiator will do a heck of a job thermal transfer wise. A big rad gives you a large amount of excess thermal transfer capacity and a 180 deg stat will keep the coolant right at 180 degs...a lower than stock temp stat is not always a good thing.

If you are hitting 180 deg F the ECU will go into normal ops - it comes out of warm-up enrichment at 176 deg F. Typically, a 195 deg stat is what you want to use (exactly for this reason), especially in your climate. Use a stock pressure rad cap (that is unless you want to blow a hose).

 

[speedfreak]

the radiator is a csf and i didnt drill out the jiggle valve hole, i just went on a long drive and it seems fine still i am using a 65%coolant to water mix. great heads up dub ill get a 195f t-stat i was hoping thats what someone credible would say just t-stat partially opening its just that a couple of days ago it would be really obvious that the whole system was pressurized to the max so i siliconed in a thermometer to measure the after tstat temps and i havn't been able to get it back to that kind of ppessure oh well at least its not too hot i guess thanks all

 

[IJ.]

"Pressure" is going to be the same both sides of the t-stat wether it's open or not.....

See the bypass lines?

 

[speedfreak]

this is off subject but i want to take advantage of your attention, i installed 7mm worth of washers in my oil pump relief valve and in the oil cooler relief valve and my pressure is high 42psi @650 rpms and 78-80psi@3000 what is the danger of high oil pressure and am i near the limit? if so how could i reduce it i use 10w30