I need to change the coolant on my 2001 4.0. According to JTIS there is a drain plug somewhere but looking under the engine (without lifting it up) I can't seem to locate anything that looks like that. Where is that drain plug hiding?

I will also change some bits of the cooling system whilst at at as preventive maintenance, like water pump, thermostat housing and some hoses. Since I have never worked on a cooling system before, is there any conventional wisdom that I should know to avoid leaks? Or is it as simple as just pull the bits off and put the new ones on, just making sure the surfaces are clean, and figure out how various clipses work?

And oh yeah, the water pump pulley, do you loosen and tighten the bolts when the belt is on?

 

The main thing I'd do whilst I was there is replace the header tank, this is the most likely thing to fail....

 

I think the drain plug will be at one side (sorry, don't know which) of the bottom of the radiator, either set vertically or maybe horizontally. They often have a cross cut into the plug that takes a coin or the like. On my car there's a splash shield fastened beneath all that stuff, so that would have to come off first.

I expect you'd need to take the belt off. When fitting the new water pump do not overtighten the bolts. If you're unsure, get a torque wrench and look up the torque in JTIS
(Likely "hand tight" for a weakling. JTIS will give an actual figure.)

BTW, I hope the new pump comes with new bolts. I'd buy them if not, but that's me. They're likely "stretch" bolts.

A fair few (maybe many) of the hoses and plastic parts will be brittle or hardened now so you "ought" to replace them but it's a major pain and not especially cheap so you have decide. You sound to be thinking along the right lines already.

 

I thought of skipping that, it was replaced five years ago and visually seems to be still in perfect condition.

 

I haven't took the splash shield off to have a look, but it must be there somewhere then.

Good point, the torque is 8Nm +90 degrees. it did not come with bolts, I'll need to order them then. Not this weekend job then..

Sure, when I ordered them from britishparts I pretty much took everything they had in the catalog related to cooling. The "extra" bits over the planned ones was not too expensive in my mind.

 

The drain is on the lower right side of the radiator. I use a short length of hose to the drain tube to route it out from the plastic under panels.

bob gauff

 

Just an update if anyone is interested or for future reference.

No surprises with thermostat housing nor pipe work. There is a DIY here about thermostat housing elsewhere. For clips, I found locking pliers invaluable since I do not have special hose clips tool. Maybe one of those would have been a good idea.

DCCV was some struggling to figure out how to detach hoses. I ended up taking DCCV and aux water pump out together with all hoses detached from the other ends which are more easy to access. Even with something to allow detaching clips in confined spaces, the hoses were pretty stuck to the DCCV and would have been difficult to remove given the limited space. On installation some lube was required to push hoses back to metal tubes with rubber o-rings.

Now, the water pump. It turned out to be a disaster. The new style pump is a bit thinner than what I had and it seemed I have to use both old and new gasket together to make the bolts fit. Alright, 8Nm plus 90 degrees it is, and I did not like the feeling at all at the end of the 90 degrees. I had to take the bolts off to see what happened and lo and behold, two of them had snapped inside the block.

Damn... ok, a bit of drilling and try some extraction tools. Nothing. I did not want to try too hard to not to break an extraction tool inside, that would be undrillable. Ordered some left hand drill bits, maybe that helps and they get unwound but no... at the end no, I really had to drill up to 5mm and retap. Even I was very careful to make them straight, at the end both holes were a bit angled and I had to shave a bit off from the water pump holes to allow bolts to go through with ease.

(Note to self. Should have used the old water pump as drilling guide with some tape around the drill bits to get them straight. Fan shroud needs to come off in this case, otherwise no drill will fit. Or maybe with an angle extension it would).

New bolts and now chop about 5mm off the length and add 3mm more thread to make sure nothing blocks them going in. I also added two washers to ease the stress on the angled bolt heads against the water pump.

I found that Alldata says 12Nm for the water pump so I used that and added sealant on both sides of the gasket to make sure leak free operation (no old gasket this time). No problems this time and no leaks.

For the water pump pulley, again conflicting information. For my year, they say 10Nm but for later years 12Nm and replace the bolts. Hmm, I did order also new bolts for the pulley, but I decided to install old ones with 10Nm and keep the new ones as spares if needed.

No problems with filling or bleeding. Since the stated capacity is 10L and I needed 7L there was quite a lot of old coolant still lurking around. After the first using of the car the level still dropped to minimum so not all air gets removed with bleeding procedure. After the second use it still seemed to down a bit. I haven't used the car for the third time yet.

tl;dr: don't change your water pump.

 

The "bleeding" is essential. I replaced my water pump, thermostat and re-hosed my 2001 XJR with 77K miles. After refiling the coolant, start the car and let it idle for about 5 minuets. Once the thermostat opens, turn on the heater to high and set the throttle to 2500 rpm. you will likely need to add a little more coolant. I kept my level just below the overflow port in the neck of the reservoir. After about 10 minutes, set the throttle back to idle and inspect the coolant for bubbles. It took almost an hour before mine completely purged all of the air. Replace the cap and turn the engine off. Let it cool down to ambient temperature and check the coolant level. Top off if necessary. Be careful to not overfill. About 1/4"-3/8" below the fill spout bottom when the coolant is at ambient temp (overfilling will cause over pressurization). My cooling fans are now back to normal when the engine is shut off. They run between zero and 2 minutes post shut down in Texas.