Meant to write this for a while now but did not get to it till today. I'm mostly a leecher on this forum and don't have enough expertise to contribute back. If you look at my posting history - you probably see that I started a coolant flush. I'm going to list out all the things I did wrong and hopefully contribute something back and help avoid others making the same mistake.

I did succeed in doing a coolant flush and replacing the thermostat and the thermostat housing. It too me a long time here is how not do it.

The saga started when I was driving down the road and low coolant light came on. I panicked looked at the engine temperate and it was fine. I drive home wait for the system to cool down and take a look and notice the coolant reservoir take is low. What started as - oh I just need to top up the coolant a bit ended up with me replacing the thermostat housing, the thermostat and coolant.

STEP 1: Find the right coolant.

I've had this car for 3 years now and I only drive it about 2k miles per year. Having not serviced the coolant previously I didn't know what was on there. On to jaguar forums then - lets find the right coolant. I should have guess I was going to in for a ride, when every thread on coolant to use was just the bit different than the other - some suggesting selecting based on color, other based on chemical composition and yet others on specification which were a bit all over the place. After spending quite a lot of time on the internet and a drive down the the jaguar dealership there was only one lesson to learn topping up coolant was out of question I was going to have to do a flush.

Lesson one - don't mix coolants.

A search on rockauto had a lot of recommendation, from orange to pink, from zerex to prestone. A trip to autozone resulted in the tech there recommending zerex. The Zerex and Prestone choices did not match was seemed like the right choice - selecting something from ford and I did not trust the tech at autozone.

@michaelh respondedLesson two - grab a ford spec coolant - WSS (it is pink in color). Without trying to find the exact spec for the particular engine I had this was good enough as long as I was doing a full flush.

I got the BECK/ARNLEY 2521021 (252-1021) concentrate from rock auto and in the few months since I've been using it the cars been working great.



Select a coolant is more art than science, get a coolant that is a ford spec and don't mix coolants. One can over think step 1 and worry about it endlessly.

STEP 2: The flush

I started by draining the coolant via the bottom of the radiator nozzle. I was initially surprised by the volume of coolant that drained (too little) until I realized there was a lot more coolant in the engine block that wasn't going to come out yet. So it was going to be cycles of (a) adding distilled water into the system (b) bringing the system temperature up to where the thermostat opened and fans turned on (c) running the heater to circulate the water thru the heater core (d) waiting for the system to de-pressurize and draining the system.

After a while about 4 flushes I started making progress, the liquid coming out was beginning to clear but was hazy. At this point I was back on the forum - there must be a better way to flush the coolant in the engine block. There was

@motorcarman responded withDraining the engine block is not easy hobbyist like me - long extension, flex joint behind the wheel arch and steering rack - this wasn't going to happen for me. I was going to have to do it the hard way.

Lesson three - flushing the coolant is going to need patience and repetition.

Back to the internet to see if there is a way to speed this up the 30-40 minute cycles, using jack stands was both tiring and tedious. At this point I noticed on YT (channel chrisfix) video when doing the flush chris removed the thermostat to speed up the flush. Seems like a good idea and I went ahead and did that. Can't say that I thought this through at the time, would running coolant thru a cold engine cause issue? Well, it didn't and it did speed thing up. Was it worth it? NO - I don't think I saved more than a couple of drains - I wouldn't recommend it, but it caused no harm to my car.

You can see pictures of my progress with each flush on some of my previous posts. Here is the result of the final flush - this took me about 10 flushes. Looks clear enough for me.



Lesson four - remember lesson three patience and repetition, the tricks to speed up the process are probably not worth it.

STEP 3: Reinstall the thermostat

I went ahead and purchased a new thermostat. Nothing but the most expensive thermostat I could find on rockauto for my car - (it was only $2 more than the rest)




This wasn't a great choice. On the existing thermostat the gasket had a slit in the center and went around the edge on the thermostat. This made the thermostat and gasket sit nicely in the housing. This one had a gasket that just sat on top, making it difficult to hold it in place vertically while you installed the thermostat cover, it also resulted in a little bit of play in the thermostat when placed. So it was going to have to be the old gasket with the new thermostat.

Lesson five - watch out for small issues that ain't quite right even when you spend the most and will cause pain if you miss them.


STEP 4: sit back and rejoice a job well done. Nah, step 4 is where I take it to a 1000 with some stupidity.

While putting back the thermostat cover and tightening the bolt, I'm not quite sure if I've tightened them enough to prevent a leak. Instead of just running another flush and observing for leaks I decide to tighten it a bit more. I know shouldn't have - SNAP - the plastic thermostat housing gives way.

Step 4 is now replacing the thermostat housing. Everyone says the cheap 20 year old plastic is going to break at some point, this is going to be a nice upgrade and aluminum thermostat housing. Back to rock auto, they have only one aluminum housing, so price isn't a consideration this time



Now this is where the fun really begin. The back bolts holding the thermostat housing down aren't easy to get it. The intake manifold gets in the way. Off to the forums and YT videos to do a lot of research. I've seen a lot of videos by @O&DR on xk8 and had learnt quite bit from those so that was the first place to look. Sure enough they had a video, which starts with - this is the intake manifold method recommended by bob motorcarman on the jaguar forms. Release a few bolts lift the intake manifold and get access the back bolts, easy enough. Lets do this.





And ... the intake manifold won't budge a millimeter. I want to be careful with this, avoid digging myself a bigger hole, back to the forum and other YT videos. I find another video where it is clear that what was in the video from o&dr isn't adequate may be even right. O&DR asks me to confirm that my engine model is correct - the vacuum actuator on the top same as in the video it is an AJ-26.

At this point @michaelh responsed to one of my queriesLesson six - take breaks. there are almost always easier ways to do things which you won't find if you don't walk away from things for a while.

STEP 5: Succeeding with getting the bolts out.

I was ready to give up and get the car towed have a professional fix it for me. But I'd already spent 3 weekends on something that should have been a few hours of work. Time to drown my sorrows in more youtube videos of people working on their xk8's. I few days in i run into an obscure 90 second video with few views of someone demonstrating the removal of the thermostat housing using a crowfoot - hell ya to the youtube recommendation algorith, hell no to how long it took to teach itself what i was looking for. Turns out, the bolts don't actually get stuck on the intake manifold there is just enough (a millimeter or two) of clearance for the bolts to come off.

After a couple of experiments with the right drive (3/8 th vs 1/4 th). I find myself a crowfoot that fits perfectly. That single crowfoot cost me $20


But it was worth every penny. It was the only place and the only one I could find.




Lesson seven: Find the right tool and you'll make more progress and faster.

STEP 6: Installing the new aluminum thermostat housing and upgrading to hex bolts in the back of the thermostat housing

it took me a while to find the right m6(? - i forget now) hex bolts but I am excited I'm almost there and the car is going to be back on the road soon. I disconnect the hoses take of the crossover pipe and .... I notice a pretty decent sized gouge on the cross over pipe that was hidden by the hose going over it.

Lesson eight: Expect the unexpected, these are old cars and someone will have been in there and may be put things back in a way not to your liking

Off to rock auto then - for a new cross over pipe, temperature sensor and thermostat bypass hose. A week later with everything in hand, I notice the cross over pipe includes all the gaskets and the temperature sensor. Pay attention to whats included with each part of you end up spending more than you need to

Back to the installation, and I try the hex bolts. The manifold is in place already and I can't actually get leverage on the bold due to the clearance between the bolt head and the manifold. Is this really an upgrade? I don't see the upgrade if I am going to have to deal with the manifold if I ever need to back back in here. Back to the tried and trusted crowfoot and regular bolts, everything goes on in a straightforward manner.

Lesson nine: Upgrades lie in the eyes of the beholder.

Irrespective of what you read on the internet or view on videos, my own experience suggest for many things the manufacturer has made a set of choices that makes sense. As a hobbyist with less experience you are always better off sticking to those choices, most things will just work if you do.

STEP 7: Refill the coolant.

Remember the note about coolant in the engine block, during on the flushes we replace the coolant with distilled water. If you purchased pre-diluted coolant the mix ain't going to be right. I got lucky in that the coolant I purchased was only available as a concentrate.

Lesson ten: Always buy concentrated coolant, you can always dilute it and keeps your options open.

Look for leaks drive the car around, run the heater, check the temperature for a few week after and if you are lucky as in my case, there will be no leaks, the reservoir will hold it's level and you will know how not to do a coolant flush, thermostat and housing replacement.


There are a few more things I screwed up along the way that I don't recall and this seems long enough as is.

Thanks

 

I am sure there are some errors / typo etc. on here and things that are a bit incoherent, took me a long time to write it down. I will come back and edit it later.

 

Great Job!!! The 4.0L is unique as to intake and coolant tower. The latter 4.2l uses the 8mm and also some have Torx Head. The 8mm also is 5/16 SAE size. Reason it is so hard to find one They are same. The 1/4" dive is best option due to more room to work. Glad you were successful.

 

Enjoyed the read. Thanks for sharing your story.

 

I guess the 3/8 drive crowfoot was simply too bulky to be of any use?

 

Yep. The entire 3/8 th set was cheaper to get than the single 1/4 th. I tried it first. It was too bulky and i ended up returning it.

 

Thnaks

 

Well done, chillyp

Good move on replacing the crossover pipe. It's made from the same biodegrading material as the OE tower, and sadly there's no aluminium replacement for it.

Sounds like you're not overly impressed with the new thermostat tower?
It's pretty much a fit-and-forget part.

 

>Sounds like you're not overly impressed with the new thermostat tower?

The aluminum housing definitely an improvement, I agree on doing this. my breaking the plastic housing definitely says worth doing without a doubt.

I thought the couple of other things that I read as improvements (a) hex cap screws for the back bolts on the housing - which I read as being as an improvement that wouldn't need messing with the manifold if I ever needed to go back in there and (b) painting the thermostat housing to prevent rust - were not for me.

I did seriously consider both those. I even tried the first and for me it felt like an objectively unnecessary (potentially worse) idea. The paint on the housing to prevent rust I did not try - I couldn't find a single example (picture or video) of the housing having rusted.