Help please- replacing thermostat, what's the easiest way to drain the coolant?

captain_k · Mar 20, 2011

I'm going to attempt to replace the thermostat on my own, the only part I'm hung up on in how to actually drain the coolant.

The official service manual says to use the drain plug on the radiator, which requires removing the headlight and grille.

The Haynes manual says to use the engine block drain plug. I got under there and can't even find the damn plug.

The guy at Autozone says to just disconnect the lower radiator hose... so which method is best?

Once I get it drained, I'm pretty confident I can replace the thermostat - I have the new thermo, a seal scraper, a new seal, and RTV. Then I just replace the fluid with 50/50 mix up to the line on the bottle, right?

xjtrailrider · Mar 20, 2011

You can get to the radiator petcock valve by removing the grill, 6 or 8 screws then reach in and loosen the petcock up.

xjtrailrider · Mar 20, 2011

The block drain plug is on the drivers side of the block near the motor mount but that plug is hard to get to.

birchlakeXJ · Mar 20, 2011

I hesitate to use the petcock. It is under-designed and prone to cracking/stripping. Plus some disassembly required.

If I'm going to drop all the fluid, I always remove the lower hose. Simple and quick.

For just the thermostat, you could also just remove the upper hose and try to direct what comes out to a waiting catch pan.

johnnyc · Mar 20, 2011

I tried to unscrew the petcock once and it snapped off. So then I had to completely remove the radiator in order to seal up the petcock hole.

Much easier to pull the lower hose.

UNCC_99XJ · Mar 20, 2011

xjtrailrider said:
You can get to the radiator petcock valve by removing the grill, 6 or 8 screws then reach in and loosen the petcock up.

And if you've got a good set of pliers, you don't even have to remove the grill...just the headlight bezel and the turn signal and use the pliers to loosen the petcock.

Replacing the thermostat is a very easy job on an XJ. You may have to remove the electric fan and/or the mechanical fan shroud to get the tstat housing completely off...I can't remember from the last time I did mine.

captain_k · Mar 21, 2011

Sounds like I'll be removing the lower rad hose. Will I need to remove anything else to get at the hose connection?

birchlakeXJ · Mar 21, 2011

captain_k said:
Sounds like I'll be removing the lower rad hose. Will I need to remove anything else to get at the hose connection?

Nope, just get underneath and use either a screwdriver for a worm gear type of clamp or something like a vice grip pliers for some factory style clamps. Very straight forward. Just have that catch pan ready when the hose comes loose.

robhurlburt · Mar 21, 2011

not sure your year, but i found it much easier to remove the air box. just 3 screws, and gives you a TON of room to work

ParadiseXJ · Mar 21, 2011

You don't have to drain the coolant to replace the thermostat. You might lose a cup or two of coolant, that's it. Two bolts.

RenegadeT · Mar 21, 2011

robhurlburt said:
not sure your year, but i found it much easier to remove the air box. just 3 screws, and gives you a TON of room to work

this^

ParadiseXJ said:
You don't have to drain the coolant to replace the thermostat. You might lose a cup or two of coolant, that's it. Two bolts.

but more importantly this^

Dragonslayer · Mar 21, 2011

I did mine 2 weeks ago. I did the same as ParadiseXJ recommends. I found that
the coolant seemed to keep dribbling out of the head without end and so I then put the
front of the car on jack stands. That tilted the engine up and stopped the coolant from
dribbling out. All that made it easier to clean and keep dry the thermo housing mating
surfaces so that the RTV could achieve a better seal when I put it all back together.

I lost about 1/3 - 1/2 gallon of coolant into the catch pan, but I think most of that came
from the upper rad tank.

ParadiseXJ · Mar 21, 2011

Dragonslayer said:
... put the
front of the car on jack stands. That tilted the engine up and stopped the coolant from dribbling out. All that made it easier to clean and keep dry the thermo housing mating surfaces so that the RTV could achieve a better seal when I put it all back together...

That's a great tip!! I'll be using that idea next time.

lawsoncl · Mar 22, 2011

Once when doing the thermostat, I just popped the radiator cap off and stuck a siphon down into the tank. Once it was automatically drained down to about halfway down the radiator tank, it was pretty painless to pull the thermostat housing.

And not, I refuse to touch those little drain valves because when the don't snap off they are flipping slow.

Help please- replacing thermostat, what's the easiest way to drain the coolant?

captain_k

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xjtrailrider

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xjtrailrider

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birchlakeXJ

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johnnyc

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UNCC_99XJ

Twisted Up

captain_k

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birchlakeXJ

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robhurlburt

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ParadiseXJ

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RenegadeT

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Dragonslayer

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ParadiseXJ

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lawsoncl

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