Thermostat replacement

Do you or do you not have to drain the radiator to replace the thermostat?

If you just pull the upper hoses and the thermostat housing, how much coolant would potentially come pouring out?

You don't have to drain the radiator. Best bet is to elevate the front so the coolant is leveled toward the back of the engine. This will keep more coolant in the engine. Then you need to either make a mess and remove the upper hose or drain a bit of the coolant out first.

Cottontail said:

Do you or do you not have to drain the radiator to replace the thermostat?

If you just pull the upper hoses and the thermostat housing, how much coolant would potentially come pouring out?

Click to expand...

You don't have to drain it fully but you will need to bring the level down a couple of pints. Don't forget to burp the cooling system when you refill.

One thing that I usually do if I want to just change the t-stat on my XJ is use a small siphon and shove it down the radiator neck and siphon out about a gallon of coolant. I do this so I don't make a mess or waste coolant.. more so on the making a mess part. My engine bay is cleaner than my apartment.

Talyn said:

One thing that I usually do if I want to just change the t-stat on my XJ is use a small siphon and shove it down the radiator neck and siphon out about a gallon of coolant. I do this so I don't make a mess or waste coolant.. more so on the making a mess part. My engine bay is cleaner than my apartment.

Click to expand...

I go one further. I have an old Holley electric fuel pump (only good to feed a carburetor...) that I use to pump coolant out of the radiator and into old antifreeze containers that I have saved for the purpose. Not saying it is the best way, just one way.

At any rate, once the coolant level is below the T-Stat's position, you can pull things part and not loose any coolant.

Just remember that is against the EPA rulings to dump coolant onto the ground. It was due to this requirement that I started pumping to begin with.

But then, I use distilled water only in all of the vehicles I own. No tap water for me, too many minerals floating about.

Remove the thermostat housing, elevate it, and replace the thermostat. The hoses can all stay attached. About 1-2 cups of coolant will come out.

If the cooling system has a cap on the radiator, the system is self burping.

I never saw it mentioned.....

Am I the only one who the part guy hands a 180deg. thermostat?

Every time? I have to hand it back. Why?

In case anyone who reads doesn't know.....

Your 'puter won't go into closed loop and your heat and MPG will suck.

Actually, you won't notice much difference between a 180* and 195* thermostat.

The thermostat temp rating pretty much only affects the temperature when it opens, at which time the other cooling system components and their condition determines the temp at which the system operates. I've recently seen statements that 180* units are available as OEM equipment for some years from the dealer but I don't know if this is true.

Don't forget to drill a 1/8" relief hole in the thermostat,
if it dosen't already have one.

Runnin'OnEmpty said:

Don't forget to drill a 1/8" relief hole in the thermostat,
if it dosen't already have one.

Click to expand...

What???

greychalet said:

I never saw it mentioned.....

Am I the only one who the part guy hands a 180deg. thermostat?

Every time? I have to hand it back. Why?

In case anyone who reads doesn't know.....

Your 'puter won't go into closed loop and your heat and MPG will suck.

Click to expand...

Sorry, Wrong. I run a 180 and the Heep goes into closed loop. ECT is the least important portion of the algorithm used to determine open/closed loop operation. My Heep operates at 90(C) degrees (194(F)) all day long. It will go as high as 93(C). That is where the fans come on line.

As for the hole issue. This must be done so that the engine will "self burp" the air. None of the aftermarket T-Stats I have every seen came with the hole. In terms of where to drill, there is, usually, a raised ring in the body of the T-Stat, drill the hole just inside of this ring. From the ring outboard, is the mating surface.

O-Gauge Steamer said:

Sorry, Wrong. I run a 180 and the Heep goes into closed loop. ECT is the least important portion of the algorithm used to determine open/closed loop operation. My Heep operates at 90(C) degrees (194(F)) all day long. It will go as high as 93(C). That is where the fans come on line.

As for the hole issue. This must be done so that the engine will "self burp" the air. None of the aftermarket T-Stats I have every seen came with the hole. In terms of where to drill, there is, usually, a raised ring in the body of the T-Stat, drill the hole just inside of this ring. From the ring outboard, is the mating surface.

Click to expand...

In researching further, I found writings to indicate that an open system (such as my 2001) doesn't require that mod, as it self burps the air as a process of the system itself.

O-Gauge Steamer said:

Sorry, Wrong. I run a 180 and the Heep goes into closed loop. ECT is the least important portion of the algorithm used to determine open/closed loop operation. My Heep operates at 90(C) degrees (194(F)) all day long. It will go as high as 93(C). That is where the fans come on line.

As for the hole issue. This must be done so that the engine will "self burp" the air. None of the aftermarket T-Stats I have every seen came with the hole. In terms of where to drill, there is, usually, a raised ring in the body of the T-Stat, drill the hole just inside of this ring. From the ring outboard, is the mating surface.

Click to expand...

O.K. I am wrong. Still doesn't explain the 180* thermostat.

The OEM is 195*...why do they hand me a 180*?

Good question.

Next question?

Seriously, some of the folk behind the counters are somewhat less than sharp. Every 4 litre out there calls for a 195 T-Stat.

I went with a 180 due to the supercharger. It should be noted though that the OEM T-Stat has an air bleed built into it.

Cottontail said:

In researching further, I found writings to indicate that an open system (such as my 2001) doesn't require that mod, as it self burps the air as a process of the system itself.

Click to expand...

Even open systems need burping its just that the process is a little different. No matter what, you will have air trapped in the system somewhere. With an open system, the best way to clear it is to turn your heater to the full "on" position and start the car with the radiator cap off. DON'T try to remove the rad cap when an engine is hot but if you start cold and let the engine build up heat until the thermostat opens, the air will be driven to the top of the rad and released. At this point, you need to add more coolant until it is full, reinstall the rad cap and you should be done. Make sure you have coolant in your overflow bottle

An open system will release pressurized air through the rad cap and will pull coolant back in from the overflow bottle as it cools which is (where the "no burping required" comments come from) but if there is a lot of air trapped, it is very common that the cool down cycle will suck your overflow bottle dry and will then proceed to suck more air in. If you keep refilling it you will eventually burp the system fully but it is much easier to just follow the process I outlined above and get as much air out as possible before you close everything up. It also doesn't hurt to squeeze the upper rad hose a couple of times to try to draw the air out.

HTH