Thermostat...

Hey,


First off I'd like to say that I've gotten fast, accurate responses to my questions here. Thank you!


Also, what a Great bunch of Guys and Gals that truly know the meaning of "It's a JEEP Thang!". I love my 88 XJ Cherokee Laredo and will keep her forever!


I just got done changing my Thermostat tonite. I'm so mad. The Parts Guy at Pep Boys gave me a 195 deg w/o the HOLE! So I had to waste a perfectly good gasket and put back in the old Thermostat until I can exchange it for one with a hole.

Would it be bad to use one w/o a hole? Can you just drill a small say 1/8 inch hole?


Thx, Phil:uhoh:

You need the hole to prevent air bubbles sticking the stat closed, unless there is a notch in the edge of the moving inside peice where it seals against the outer ring. You can drill one but I'd use a little smaller bit unless its not very cold where you live. Make sure you install it with the bleed hole at the 12:00 position if you want it to work right.

FYI...The last Mopar stat I bought at a dealer was only around $12.00 and it works perfectly. I never had any good luck with non OEM stats in cold weather.

Hey,


Here's another Thermostat Q. Since the Parts Guy at Pep Boys gave me a 195 deg w/o a hole I opted to leave the Mopar one in but I had to waste a perfectly good gasket (Mad).

So, here's the prob: I changed the closed to open rad system and I have my Dual Electric Fans set to kick in at 210+. I noticed that the Fans kick in at that Temp but the Upper Rad Hose Remains HARD for a few mins more before the Thermostat (Mopar 195 deg) Opens allowing Coolant to flow.

I'm using the Dash Temp Guage. Could it be that setting the Temp to activate the Fans by it is inaccurate hence the Thermostat opening a few min after the Fans turn on? IOW - When the Thermostat opens at 195 deg? Hope I'm making sense.


Thx, Phil

Where did you mount the sensor for the fans?

Where did you mount the sensor for the fans?

Hey Saudade,


I mounted it where the Upper Radiator Hose goes as per Flex-A-Lite's instructions. The Sensor Probe is mounted inside the Upper Inlet. It's basically a copper bulb on copper tubing going back to the control box. You can set the Fans to activate anywhere from 180-240 degrees.

Regarding the Thermostat, etc. :

I went to Pep Boys to exchange the Thermostat for one with a hole. Unfortunately NONE of them had a hole? I then went to four other Auto Part Stores and the same there; NO HOLE.

The only Thermostat that I could find that was different was a "Fail Safe" type. It's designed to blow open and prevent the engine from further overheating.

Q1. Anyone know if this "Fail Safe" type will do the same as one with a "Hole"? Hope I'm making sense.

I think the only place that I can get one with a hole is from Jeep Mopar. But the dealer's price is usually pretty high. Don't wanna waste money on a part when the above can do the job.

Q2. How about Synthetic Oil for the 4.0L Engine? Will using it hurt this engine (mine's a reman).

Q3. Speaking of Synthetic Oil, I heard (don't know how valid it is) that Castrol Syntec, and many other "SYNTHETICS" are NOT SYNTHETIC just purified, hydrocracked regular oil. Anyone heard about this?

Q4. How "Hard" should the Upper Rad Hose be when the vehicle's warmed up and the Thermostat Opens? Mine goes from ROCK Hard to just a little softer (it's subjective so it's hard to explain).



Thx, Phil

Hey Saudade,


I mounted it where the Upper Radiator Hose goes as per Flex-A-Lite's instructions. The Sensor Probe is mounted inside the Upper Inlet. It's basically a copper bulb on copper tubing going back to the control box. You can set the Fans to activate anywhere from 180-240 degrees.

Regarding the Thermostat, etc. :

I went to Pep Boys to exchange the Thermostat for one with a hole. Unfortunately NONE of them had a hole? I then went to four other Auto Part Stores and the same there; NO HOLE.

The only Thermostat that I could find that was different was a "Fail Safe" type. It's designed to blow open and prevent the engine from further overheating.

Q1. Anyone know if this "Fail Safe" type will do the same as one with a "Hole"? Hope I'm making sense.

I think the only place that I can get one with a hole is from Jeep Mopar. But the dealer's price is usually pretty high. Don't wanna waste money on a part when the above can do the job.

Q2. How about Synthetic Oil for the 4.0L Engine? Will using it hurt this engine (mine's a reman).

Q3. Speaking of Synthetic Oil, I heard (don't know how valid it is) that Castrol Syntec, and many other "SYNTHETICS" are NOT SYNTHETIC just purified, hydrocracked regular oil. Anyone heard about this?

Q4. How "Hard" should the Upper Rad Hose be when the vehicle's warmed up and the Thermostat Opens? Mine goes from ROCK Hard to just a little softer (it's subjective so it's hard to explain).



Thx, Phil

Phil,
A fail safe stat is usually designed to lock in the open position if it gets too hot. Most of the quality stats I've seen are this way. The bleed hole in the factory stat was to assist in the initial fill up and purging of air so th e stat doesn't stick closed. The secondary benefit is that a small flow will help the stat sense a more accurate engine temp and open a little sooner.

The hoses will be pretty hard warm or hot since the system is under about 15 psi. They stay pretty firm even when the t-stat opens fully. This pressure is what raises the coolants boiling point to operate at 220F. The only times I remember seeing the upper hose go soft was during the initial burping after refilling.

Any synthetic oil will be fine in the 4.0l engine. Just remember to change it at normal intervals. i gets dirty just as fast as regular oil.

I don't know anything about the chemical makeup of the synthetics, but at the Jeep factory training I attended, the general comment was the even regular oil never wears out, it just gets dirty and the additives break down with use. Thus the ability to rerefine used oil to start anew.

I hope some of this helps.

Phil,
A fail safe stat is usually designed to lock in the open position if it gets too hot. Most of the quality stats I've seen are this way. The bleed hole in the factory stat was to assist in the initial fill up and purging of air so th e stat doesn't stick closed. The secondary benefit is that a small flow will help the stat sense a more accurate engine temp and open a little sooner.

The hoses will be pretty hard warm or hot since the system is under about 15 psi. They stay pretty firm even when the t-stat opens fully. This pressure is what raises the coolants boiling point to operate at 220F. The only times I remember seeing the upper hose go soft was during the initial burping after refilling.




Hey OlJeepTek,


So a Stat with a bleed hole can still get stuck closed? If so then is the Fail Safe Stat actually better than one with a hole? Does the Fail Safe Stat need a bleed hole too or no?

Also, when I changed my closed system to an open radiator system I used a STANT Radiator Cap with a LEVER on top. This Cap says on it 13psi is that rating ok or do I need a higher one?


Thx, Phil
ps You Guys are so knowledgable! I'm glad I found a responsive site for the vehicle we enjoy so much!

According to the Castrol website, Syntec is a "fully synthetic oil". The merits of synths over petrol based oils (at least, high quality ones) have always been a highly "discussed" topic on here are other forums.

Hey OlJeepTek,


So a Stat with a bleed hole can still get stuck closed? If so then is the Fail Safe Stat actually better than one with a hole? Does the Fail Safe Stat need a bleed hole too or no?

Also, when I changed my closed system to an open radiator system I used a STANT Radiator Cap with a LEVER on top. This Cap says on it 13psi is that rating ok or do I need a higher one?


Thx, Phil
ps You Guys are so knowledgable! I'm glad I found a responsive site for the vehicle we enjoy so much!

Sure. Any stat can stick open or or stick closed. The bleed hole will help prevent an air bubble from being trapped against the bulb of the stat, thereby preventing it from accurately sensing actual engine temp and mimicing a stuck stat by opening late.

I'm not sure which brand "Fail Safe" stat you were looking so I won't try to guess what it is touting to do. Mostly the ones I have worked with it means they pop open if radically overheated and lock open. They are shot after that.

In my experience, I learned the hard way to stay with the factory stat here in Minnesota. The others didn't didn't hold the temp high enough in winter. I have seen very few Mopar stats stick shut.

As far as the cap goes, 13 psi should be fine. If its not, it will boil over or burp coolant regularly. Stant caps always worked wel l for me.

I'm not sure which brand "Fail Safe" stat you were looking so I won't try to guess what it is touting to do. Mostly the ones I have worked with it means they pop open if radically overheated and lock open. They are shot after that.





Hey OlJeepTek,


Just check the package this eve. It's made by MOTO RAD. Made in Israel and I bought it at AUTOZONE. Cost around $14 with tax.

Doesn't have a hole in it just the clips that hold it open.

Should I drill a 1/8" hole in it?


Thx, Phil

Hey OlJeepTek,


Just check the package this eve. It's made by MOTO RAD. Made in Israel and I bought it at AUTOZONE. Cost around $14 with tax.

Doesn't have a hole in it just the clips that hold it open.

Should I drill a 1/8" hole in it?


Thx, Phil

I'd drill it. Make sure the hole goes in at 12:00 position. You might drill it a little smaller if you live in a very cold climate such as here in Minnesota. It helps squeeze a few more degrees from the heater when it's below zero....