T-stat issue resolved and why it happened. With pics.

[IwantMKIII]

First off thanks for pointing this issue out to those who helped...even if it may have been frustrating for you :biglaugh: . Here's why it was happening:

I don't know why the builder decided to do this but he had some type of reasoning behind it since he supposedly builds 7m's all the time for racing purposes. BTW he was a professional and this build was done during regular shop hours....not like paid on the side or something

Either way, i have a new Super Stat installed (192-195*). Heated up much quick to about 160*, after that it took a quite a bit longer to warm up. It averages about 190-195 however i still think i should've gone the 180* T-stat route. I find that after even one boost pull in third 3K to maybe 5.5K RPM my temps quickly rise to 200+ which was my fear with the 192vs.180. I have yet to do a full boost run...ie from 1st through 4th or so to see how that handles but well see....i started running low on gas and wanted to make sure the cover was sealed properly so i didn't do it yet. I will edit this post if the temps exceed far beyond 210 in a full boost run.

 

[Dan_Gyoba]

So... Basically no thermostat at all then.

I had mine stick open. It was horrible. The car would only ever warm up if it was freaking HOT outside. When the weather turned cold, it wouldn't warm up at all.

 

[IwantMKIII]

So... Basically no thermostat at all then.

I had mine stick open. It was horrible. The car would only ever warm up if it was freaking HOT outside. When the weather turned cold, it wouldn't warm up at all.

basically. My question is why even bother cutting it?

 

[IJ.]

It's an old school mod....

In some motors if you totally remove the T Stat the motor will actually overheat as the water moves through the Rad too fast so you gut the T Stat.

Moroso sell "kits" with different sized plates.

 

[Dan_Gyoba]

I used to know guys with big block V8s that would do this kind of thing. The idea being that on the hard drag runs, the thermostat was too much of a restriction in the coolant circulation. Removing the thermostat supposedly allowed things to cool more and faster.

But even those guys would only do that for a drag engine, never on a street or track engine.

 

[jetjock]

i still think i should've gone the 180* T-stat route. I find that after even one boost pull in third 3K to maybe 5.5K RPM my temps quickly rise to 200+ which was my fear with the 192vs.180

You still don't get it.

 

[jdub]

Now that that issue is resolved
And, did you cut the jiggle valve off?

The middle of your old stat was cut out so it would hold the rubber gasket around it in place. I hope you got a new one for the new stat. Your builder did this because he likely learned it (on V-8's) per the comments above...he does not, however, know how the 7M ECU uses coolant temps to modify fuel and timing.

A 180 deg stat is not going to help...if your coolant system does not have the thermal capacity or parts of it are not up to speed, your temps will still hit the same peaks. A colder thermostat will just delay it a bit...your radiator still has to transfer the heat to the air (this is your issue now)...pay attention in your thermodynamics class

How quickly does temps drop after a run and is the peak less than 210 deg?

Other things to check:
1) Is your fan shroud in good conditions...no cracks or pieces missing.
2) Is your fan clutch working properly?
3) Is there an under tray installed?
4) Is the radiator in good shape...no clogged passages or excessive deposits.
5) Is the coolant old? What type coolant and percentage mix of coolant to water are you running?

Might be a good idea to have the system pressure tested as well.

 

[IwantMKIII]

Now that that issue is resolved
And, did you cut the jiggle valve off?

The middle of your old stat was cut out so it would hold the rubber gasket around it in place. I hope you got a new one for the new stat. Your builder did this because he likely learned it (on V-8's) per the comments above...he does not, however, know how the 7M ECU uses coolant temps to modify fuel and timing.

A 180 deg stat is not going to help...if your coolant system does not have the thermal capacity or parts of it are not up to speed, your temps will still hit the same peaks. A colder thermostat will just delay it a bit...your radiator still has to transfer the heat to the air (this is your issue now)...pay attention in your thermodynamics class

How quickly does temps drop after a run and is the peak less than 210 deg?

Other things to check:
1) Is your fan shroud in good conditions...no cracks or pieces missing.
2) Is your fan clutch working properly?
3) Is there an under tray installed?
4) Is the radiator in good shape...no clogged passages or excessive deposits.
5) Is the coolant old? What type coolant and percentage mix of coolant to water are you running?

Might be a good idea to have the system pressure tested as well.

No more jiggle valve, hacksawed it off. I saw what you were talking about right away, how if it sets just right under pressure it would cause a block.


You hit the nail on the head. I understand the thermal peaks your talking about however, keep in mind these peaks are completely dependent on outside air temps at this point as the cooling system is working as efficiently as it can with the current setup....and it obviously is quite capable of cooling quickly as you saw from my op temps i posted in the other threads. Right now with temps pushing in the 20's and 30's i can cool the water temps rather quickly after a longer boost pull, however summer time is what im more concerned about. That extra 10* can possibly keep me out of a 'time pulling' situation if i were in the middle of a longer 'high' boost pull.

You're right though, i need to get a new undertray....mine was basically destroyed during the rebuild i just never got around to getting another, it would've been an annoyance anyway with how often i work under the car. This can add quite a bit of airflow to the rad not to mention highway MPG so ill see just how much it affects the cooling ability of the Fluidyne radiator after i track one down and have some extra $$$.

 

[IwantMKIII]

You still don't get it.

....then what is it.....?

 

[Frank Rizzo]

Where did you install the temp sensor for your gauge?

I have a 180 stat, I see peak temps of 205 on the highway, up a mile long hill, full boost, 90 degree humid summer weather.

If I stay out of full boost, I can keep temps around 190 all day long.

Ambient temps factor in as well as cooling system health. I find it hard to see 200F in sub freezing temps. I have a new stock radiator, fan clutch and waterpump. Fan shroud, yes, undertray or whatever you call the plastic piece that covers the underside of the engine, no.

 

[jdub]

If you're going just over 200 deg after a hard run, you are doing well with a stock radiator. Also, the 210 deg ECU temp is based on a chart...it could be slightly higher. At normal cruise, 190 deg is perfect. If you want a drag car, you'll need a bigger radiator

You have to think of the thermostat as the regulator, but the radiator as what actually gets rid of the heat. A stat also doesn't "snap" open at rated temp or close the same way either. Most stats start opening at ~20 deg before their rated temp as to be full open at rated temp. A 180 deg stat is only useful IMO when OAT is sustained above 100-105 deg for a week or more.

Do this: Take it to highway speed (60-80) for 15-20 min and observe what the coolant temp does. If it slowly climbs, you need an undertray. If it climbs during city traffic (stop & go), you need to take a look at the fan shroud and fan clutch.

 

[IwantMKIII]

If you're going just over 200 deg after a hard run, you are doing well with a stock radiator. Also, the 210 deg ECU temp is based on a chart...it could be slightly higher. At normal cruise, 190 deg is perfect. If you want a drag car, you'll need a bigger radiator

You have to think of the thermostat as the regulator, but the radiator as what actually gets rid of the heat. A stat also doesn't "snap" open at rated temp or close the same way either. Most stats start opening at ~20 deg before their rated temp as to be full open at rated temp. A 180 deg stat is only useful IMO when OAT is sustained above 100-105 deg for a week or more.

Do this: Take it to highway speed (60-80) for 15-20 min and observe what the coolant temp does. If it slowly climbs, you need an undertray. If it climbs during city traffic (stop & go), you need to take a look at the fan shroud and fan clutch.

like i said....no stock, Fluidyne radiator :icon_bigg . Highway is fine, however the undertray is a necesary item for not only cooling but MPG as well. I will have a better idea of how it reacts to longer drives today...i have a 2 hour trip ahead of me.

Read here:

http://www.toyotanation.com/forum/t74629.html <--- great write up on a forum i used to belong to. The guy who wrote it really knows his stuff, he is an owner of a MKIV, 550+WHP '94 camry, and a few others. Obviously our car isn't a camry but you get the idea on its importance.

 

[IwantMKIII]

Where did you install the temp sensor for your gauge?
192
I have a 180 stat, I see peak temps of 205 on the highway, up a mile long hill, full boost, 90 degree humid summer weather.

If I stay out of full boost, I can keep temps around 190 all day long.

Ambient temps factor in as well as cooling system health. I find it hard to see 200F in sub freezing temps. I have a new stock radiator, fan clutch and waterpump. Fan shroud, yes, undertray or whatever you call the plastic piece that covers the underside of the engine, no.

Well i checked your profile, all i can really say im outting quite a big more power when i boost than you and might be the reason why i run hotter

 

[jdub]

I missed you had a Fluidyne rad...no wonder your temps dropped like they did with no stat

Keep something in mind: You are in high boost runs for only a small percentage of the time. You want your coolant temps to be as close as possible to 190 degs for the majority of the time...if temps climb, but come right down after a run it should not be a problem. Make sure your fan shroud and clutch are in good shape and get an undertray installed.

One other thing to consider is upgrading the oil cooler and changing to a full flow thermostat controlled cooler circuit. That will help the motor get rid of heat too.

 

[IwantMKIII]

I missed you had a Fluidyne rad...no wonder your temps dropped like they did with no stat

Keep something in mind: You are in high boost runs for only a small percentage of the time. You want your coolant temps to be as close as possible to 190 degs for the majority of the time...if temps climb, but come right down after a run it should not be a problem. Make sure your fan shroud and clutch are in good shape and get an undertray installed.

One other thing to consider is upgrading the oil cooler and changing to a full flow thermostat controlled cooler circuit. That will help the motor get rid of heat too.

has been on my agenda but keeps getting pushed off by little things like these.

 

[Frank Rizzo]

Well I know people making 400whp and their coolant temps are as low or lower than mine. Last time I took a ride in one, coolant temp never got above 195F, this is on pump gas and 23psi. On a stock radiator. You should flush your radiator out, it sounds to me that it is obstructed or the flow is reduced from sediment. 166K? Yeah, I've never seen a clean cooling system on any vehicle with that amount of use unless the coolant was flushed religously. Even if you just flushed it, do it again.

You still never told us where you installed the temp sending unit. This plays a vital role in the temperatures you are seeing.

 

[Adjuster]

My guess is your fan clutch is shot/worn out.

The Fluidyne cools pretty well, even without the undertray in place. (But your stock fan shroud, fan and clutch have to be in good working order, or in place.)

E-fans, shroudless stock fans, and worn out stock fan clutches all contribute to a sickly, or fickle cooling system, even with a larger capacity radiator like the Fluidyne.

A few years ago, mine would overheat in traffic with the AC on. Turns out it was the fan clutch. (At the time, I was not running the undertray, and actually don't have the undertray in place right now, but my car is not running yet from a few other mods... )

Anyway, the solution was 80.00 from NAPA and a new fan clutch. (Hayes IIRC.)

I have the stock waterpump mounted fan/clutch, stock shroud and shroud fan on the left side plus the pusher fan on the front of the condensor between the intercooler/condensor. I also run an RX7 oil cooler that has all the engine oil passed through it after being filtered.

High boost, or high speed, it was rock solid in the control of the engine temps, especially at high speed with the undertray in place.

I'm going to add some vents to my hood to remove hot air possibly, just to make it even more effective now with the larger turbo.

Underhood temps have been cut way back with coatings and wraps too. (And this makes a serious difference from day to day, especially in traffic I've noticed.. The DP is wrapped down past the transmission, and that cut down on ambiant heat radiated to both the trans, and the floorpan of the car on long drives in the 100+ summer weather around here.) Basicly my DP is wrapped to the cat back flange. A mod I reccomend highly.

 

[IwantMKIII]

Well I know people making 400whp and their coolant temps are as low or lower than mine. Last time I took a ride in one, coolant temp never got above 195F, this is on pump gas and 23psi. On a stock radiator. You should flush your radiator out, it sounds to me that it is obstructed or the flow is reduced from sediment. 166K? Yeah, I've never seen a clean cooling system on any vehicle with that amount of use unless the coolant was flushed religously. Even if you just flushed it, do it again.

You still never told us where you installed the temp sending unit. This plays a vital role in the temperatures you are seeing.

Never seen my system then :icon_bigg . Temp unit is on the stock location. My temps are higher probably because the shroud broke off, didn't think it would effect it so much. Currently i'm looking for a new one that wont kill the look of my engine bay like the stockers do, or ill go e-fans but they are quite expensive (for the ones made for our cars); know any that don't cost an arm and a leg?

 

[IwantMKIII]

My guess is your fan clutch is shot/worn out.

The Fluidyne cools pretty well, even without the undertray in place. (But your stock fan shroud, fan and clutch have to be in good working order, or in place.)

E-fans, shroudless stock fans, and worn out stock fan clutches all contribute to a sickly, or fickle cooling system, even with a larger capacity radiator like the Fluidyne.

A few years ago, mine would overheat in traffic with the AC on. Turns out it was the fan clutch. (At the time, I was not running the undertray, and actually don't have the undertray in place right now, but my car is not running yet from a few other mods... )

Anyway, the solution was 80.00 from NAPA and a new fan clutch. (Hayes IIRC.)

I have the stock waterpump mounted fan/clutch, stock shroud and shroud fan on the left side plus the pusher fan on the front of the condensor between the intercooler/condensor. I also run an RX7 oil cooler that has all the engine oil passed through it after being filtered.

High boost, or high speed, it was rock solid in the control of the engine temps, especially at high speed with the undertray in place.

I'm going to add some vents to my hood to remove hot air possibly, just to make it even more effective now with the larger turbo.

Underhood temps have been cut way back with coatings and wraps too. (And this makes a serious difference from day to day, especially in traffic I've noticed.. The DP is wrapped down past the transmission, and that cut down on ambiant heat radiated to both the trans, and the floorpan of the car on long drives in the 100+ summer weather around here.) Basicly my DP is wrapped to the cat back flange. A mod I reccomend highly.

Shroud is broken, didn't think it would cause such a big change in temps. Fan clutch is definately good, it was "tested" almost everyday this past summer. I'm interested in your heat wrap though of the DP. I have to take mine off soon and i was wondering how you do that and what material you use and where to get it. Did you notice any significant changes in bay temps?

 

[starscream5000]

The DP is wrapped down past the transmission, and that cut down on ambiant heat radiated to both the trans, and the floorpan of the car on long drives in the 100+ summer weather around here.) Basicly my DP is wrapped to the cat back flange. A mod I reccomend highly.

I concur, I've done this as well .