Thermostat

Jsamps1345 · **Posted:** Fri Oct 28, 2016 2:50 pm

this is what i found on rock auto when i looked up the thermostat. It looks to be sealed like the jeep.

geordi · **Posted:** Fri Oct 28, 2016 4:38 pm

Definitely looks to be a sealed unit, but I see one "middle" outlet that would always be open (probably to the coolant bottle, this would match our middle port) and one possible bypass port that could feed either the viscous heater or loop directly to the pump intake.

Our thermostat has two "middle" ports, one for the viscous and the other for the coolant bottle. These are *always* open and flowing whether the bypass is open or not. The bypass drops directly to the intake, and is joined by the loop from the heater core (also a 3/4" diameter flow) as well as the 1" from the coolant bottle that receives the 1/4" feeds from the thermostat middle and the top-drivers-side of the radiator. That is how the water bottle is an active participant in the coolant loop, and how air is supposed to find its way to the bottle to be replaced by coolant.

So even if the bypass and the large outlet from the thermostat are closed, the 3/4" to the viscous heater and the outgas lines are still both flowing.

At no point is water ever "trapped" in the engine or head.

flash7210 · **Posted:** Fri Oct 28, 2016 6:33 pm

geordi wrote:

So even if the bypass and the large outlet from the thermostat are closed, the 3/4" to the viscous heater and the outgas lines are still both flowing.

At no point is water ever "trapped" in the engine or head.

You forgot one.
The egr cooler.

I made the same argument.
Until I gathered this hasty survey.
http://www.lostjeeps.com/forum/phpBB3/viewtopic.php?f=5&t=84411&start=0
Only 6 respondants.
4 reported a cracked head while using the inline thermostat.

Yes, its a poor survey. Buts its all I have to go on.
Few crd owners report here. And even fewer provide details about significant part failures.
If we could get casting dates off every failed head it might be possible to identify a bad batch of castings/assemblies.

Locked KJ · **Posted:** Fri Oct 28, 2016 10:30 pm

I think trying to get a list of casting dates is a great idea. I'm gonna take a look at my bad head tomorrow and see what numbers I can pull off of it.

WolverineFW · **Posted:** Fri Oct 28, 2016 11:19 pm

blk05liberty wrote:

justinmc wrote:

joelukex4 wrote:

Yes, 3/32 or 1/8 inch hole is all you need. Two screw clamps. One to hold the radiator hose to the OEM thermostat and a second holding the in-line thermostat as close to the OEM housing as possible. The head of the in-line will actually be inside the OEM thermostat housing. This way the inline will heat up as soon as it can and also so the pressure won't push it into the hose. Some people have said that if it is not clamped they have seen the in-line travel all the way through the radiator hose to the radiator.

The other item that has helped control temperature if you live in the north is a Fia Winter Front. I use it all the time and it is a great addition for adjusting air control.

OOO Fia winter front, exactly what I was looking for. Thanks! Definatly getting one of those!

Hey man.....you were told that cardboard wouldn't work.....so why would a winter front? ROLTFLMAO!!

Sent from my SM-N910W8 using Tapatalk

Ceearedeedriver · **Joined:** Fri May 06, 2016 8:44 pm **Posts:** 177

WolverineFW wrote:

blk05liberty wrote:

OOO Fia winter front, exactly what I was looking for. Thanks! Definatly getting one of those!

Hey man.....you were told that cardboard wouldn't work.....so why would a winter front? ROLTFLMAO!!

I've got two words for you, krazy karpet. Cheaper than a fia, won't get soggy like cardboard and you can color coordinate it with your vehicle.

WolverineFW · **Posted:** Sat Oct 29, 2016 11:15 am

Ceearedeedriver wrote:

WolverineFW wrote:

blk05liberty wrote:

OOO Fia winter front, exactly what I was looking for. Thanks! Definatly getting one of those!

Hey man.....you were told that cardboard wouldn't work.....so why would a winter front? ROLTFLMAO!!

I've got two words for you, krazy karpet. Cheaper than a fia, won't get soggy like cardboard and you can color coordinate it with your vehicle.

Even cheaper...corrogated plastic...pic your colour to accessorize your vehicle.

Sent from my SM-N910W8 using Tapatalk

jws84_02 · **Posted:** Sat Oct 29, 2016 12:09 pm

Hey man.....you were told that cardboard wouldn't work.....so why would a winter front? ROLTFLMAO!!

[/quote]
I've got two words for you, krazy karpet. Cheaper than a fia, won't get soggy like cardboard and you can color coordinate it with your vehicle.[/quote]
Even cheaper...corrogated plastic...pic your colour to accessorize your vehicle.

Sent from my SM-N910W8 using Tapatalk[/quote]

That's what I use. I have 2 different grilles. I just swap the whole thing

blk05liberty · **Posted:** Sat Oct 29, 2016 9:27 pm

. Lol!! I did go with a fia. Probably won't work because someone said so lol.

justinmc · **Posted:** Sun Oct 30, 2016 8:30 pm

flash7210 wrote:

Quote:

Someone should point a thermal camera at the engine and see if it picks up this assumed problem because otherwise it's speculation. Having an inline thermostat installed while a problem occurs may or may not be related depending on other factors that could have changed at the same time.

Sounds like a great idea. Are you volunteering to do that?
Not sure how well it would work considering you would only see temp on the outside surface of the head. You wouldn't see whats happening in the passages inside the head.
My head had cracks around the exhaust valve seats of cylinders 2, 3, and 4.

I took some thermal pics this morning as my engine was warming up from 3C to 61C (since my thermostat is broken/open flow). Not sure if it helps but here are the pics. Taken from the front left side of the vehicle.

flash7210 · **Posted:** Sun Oct 30, 2016 9:05 pm

That wiring harness sure covers up a lot.
Im surprised the fuel rail isnt hotter.

Cool images though. Thanks for sharing.

geordi · **Posted:** Sun Oct 30, 2016 10:49 pm

Dang... Now I want to buy an FLIR camera and mess with it. Cool images.

joelukex4 · **Joined:** Thu Sep 29, 2011 4:54 pm **Posts:** 386

flash7210 wrote:

geordi wrote:

So even if the bypass and the large outlet from the thermostat are closed, the 3/4" to the viscous heater and the outgas lines are still both flowing.

At no point is water ever "trapped" in the engine or head.

You forgot one.
The egr cooler.

I made the same argument.
Until I gathered this hasty survey.
http://www.lostjeeps.com/forum/phpBB3/viewtopic.php?f=5&t=84411&start=0
Only 6 respondants.
4 reported a cracked head while using the inline thermostat.

Yes, its a poor survey. Buts its all I have to go on.
Few crd owners report here. And even fewer provide details about significant part failures.
If we could get casting dates off every failed head it might be possible to identify a bad batch of castings/assemblies.

I mentioned the coolant flow vs trapped in the head to TDF back in one of the other Thermostat discussions and he totally blew it off. At no time is the flow of coolant shut off. It is just being re-routed to not include the radiator.

I use the Fia winter front to about 75F. it looks good with the grille blocked off in black and I can open the 2 vents to allow air flow in if needed.

flash7210 - I didn't respond to your survey because I didn't have any issues with the in-line for 50K. No cracked head or blown head gasket.

justinmc · **Posted:** Wed Nov 02, 2016 7:40 pm

joelukex4 wrote:

I mentioned the coolant flow vs trapped in the head to TDF back in one of the other Thermostat discussions and he totally blew it off. At no time is the flow of coolant shut off. It is just being re-routed to not include the radiator.

It seems very unlikely that a in-line thermostat would cause head cracking issues. Like you say with the factory thermostat, whether failed or working, open or closed, allows flow through the engine.

justinmc · **Posted:** Fri Nov 04, 2016 5:14 pm

Update: So I bought a used thermostat off ebay from a guy who said it worked and when I installed it my jeep is still not getting hot. He claims it's because of air in the system and that I need to do a vacuum coolant fill. But if that's the case wouldn't it overheat? I can drive and idle forever and it only gets to 64C (147F) at most.

I compressed the upper radiator hose a few times to get most of the air out and it seems that coolant is flowing through the hose and radiator. I had read that the engine will purge the air out automatically after heating and cooling a couple of times.

I had tried to test the thermostat before installing and it opened after pouring hot water through it and it was a better seal when cold than my old thermostat assembly so I figured it would work.

Now my theory is that it's opening at a lower temp than it is supposed to, does that makes sense? I'm probably going to add an an in-line thermostat to see if that will fix the under heating issue and improve my MPG a little.

Long term I'll probably modify the original thermostat assembly to bolt together and accept a drop in thermostat

Justin.

geordi · **Posted:** Fri Nov 04, 2016 8:11 pm

Probably what you bought "works" from the standpoint that it is closed when at room temp, but as you discovered, it is opening at a lower temperature than it should... Which is what happens when they are "weak" as a precursor to "failed open" which is basically that they open at a VERY low temp.

It is odd that the spring would be the thing that weakens so easily, and that the wax pellet that drives the pin is able to move the thermostat, the usual failure method I have heard of (not on these) is that the wax leaks out and that is why they never move. That would be failing closed though. These (as you have discovered) fail open, so either the wax has become more reactive to low temperatures (unlikely as this would be a chemical state change) or the spring is just poor quality metal from China. That seems much more likely.

Ceearedeedriver · **Joined:** Fri May 06, 2016 8:44 pm **Posts:** 177

geordi wrote:

....so either the wax has become more reactive to low temperatures (unlikely as this would be a chemical state change) or the spring is just poor quality metal from China. That seems much more likely.

I've dissected a couple of them and found coolant in the wax cavity when I pulled out the plungers on both of them. I believe that this contamination is the failure mode and it's moving the setpoint rather than sticking open.

lacabrera · **Posted:** Sat Nov 05, 2016 8:00 am

justinmc wrote:

Update: So I bought a used thermostat off ebay from a guy who said it worked and when I installed it my jeep is still not getting hot. He claims it's because of air in the system and that I need to do a vacuum coolant fill. But if that's the case wouldn't it overheat? I can drive and idle forever and it only gets to 64C (147F) at most.

I compressed the upper radiator hose a few times to get most of the air out and it seems that coolant is flowing through the hose and radiator. I had read that the engine will purge the air out automatically after heating and cooling a couple of times.

I had tried to test the thermostat before installing and it opened after pouring hot water through it and it was a better seal when cold than my old thermostat assembly so I figured it would work.

Now my theory is that it's opening at a lower temp than it is supposed to, does that makes sense? I'm probably going to add an an in-line thermostat to see if that will fix the under heating issue and improve my MPG a little.

Long term I'll probably modify the original thermostat assembly to bolt together and accept a drop in thermostat

Justin.

The life expectancy of theses original thermostats are short, with the work involved in replacing them Its a bit like using second hand engine oil. Buy new only.

WWDiesel · **Posted:** Sat Nov 05, 2016 9:54 am

Ceearedeedriver wrote:

I've dissected a couple of them and found coolant in the wax cavity when I pulled out the plungers on both of them. I believe that this contamination is the failure mode and it's moving the setpoint rather than sticking open.

That makes a lot of sense and is a logical explanation as to their failure mechanism!
Thank God they do not fail in the closed position or we would all be having a totally different discussion!!!! :grim:

And, I agree with lacabrera, I would never use a "used" thermostat when new is available; to riskey!!! :roll:

justinmc · **Posted:** Sat Nov 05, 2016 12:34 pm

lacabrera wrote:

The life expectancy of theses original thermostats are short, with the work involved in replacing them Its a bit like using second hand engine oil. Buy new only.

I'm well aware of that but I bought it for $30 including shipping so I wasn't expecting a lot. The seller who is a mechanic did claim it was working. My back up plan is to use an in-line thermostat and modify my old thermostat assembly to bolt together to take a drop in thermostat anyway.

Thermostat

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