My heat rapidly dropped off the other day. I've done hours of scrolling through the archives. I put my hand on the auxiliary water pump with heat on high, AC engaged and engine running and it feels as if it is running, though those could be vibrations from the engine I feel. I plan to go to my local indy this week with this request: 1) backflush the heater core with whatever descaler is appropriate, maybe a couple times; and 2) test the operation of the pump and, if it's dead, replace it. (At 75 with no great stock of tools and no garage in which to work I have to hire out most everything.)

While I suspect they have access to AllData, am I correct that to backflush the heater on an '03 XJ8 model you put water into the suction/return line attached to the center of the auxiliary water pump and the return water is cycled back through and exits from the hose attached to the pressure side of the pump, the one exiting horizontally?

If I am wrong, can someone clearly describe the proper water-in/water-out points.

Thanks. And winter can't die quickly enough in the DC area for me!

 

https://www.jaguarforums.com/forum/x...r-pump-152840/

https://www.jaguarforums.com/forum/x...r-valve-26589/

I did mine earlier this winter. First ran clean water through the core to clear out all the coolant. Poured a gallon of CLR into a bucket, arranged the hoses of a small fluid transfer pump to circulate the CLR through for a few hours. Then flushed with clean water for multiple cycles, again a few hours, before reconnecting everything and refilling with coolant. Started with flushing backwards, but also ran it forwards again after it started flowing more freely. Fairly easy and made it like new again. Put a few wood pellets in the car and smoke a brisket now.

motorcarman posted a Jaguar technical service bulletin describing the dealership flush procedure but I'd watched a bunch of videos online and thought it a superior process to just disconnect the heater core hoses and flush the crap out of the core straight into a bucket and not back through the rest of the system. The CLR dissolved much of it completely I'm sure but there were a few "chunks" of I suppose mineral deposit that it just loosened and came out into the bucket. Strained out the chunks, poured the CLR back in the bottle and it still cleaned up a shower head so its reusable for dozens of uses around the house (or the next car), don't know how many times. The fact that Jaguar issued a TSB tho indicates that a flush is very likely the correct solution or at least the first thing to try.

 

With the background vibrations coming from a running engine maybe not have it running and move the heat control to heat from A / C position and see if you can pick up electric motor vibrations

This electric motor will be running at all times in heat position and the coolant solenoid valve will regulate coolant flow to maintain cabin temp setting

There is a water shut off valve that modulates open and closed to maintain your set cabin temp that can be tested

There is a cabin temp sensor by the drivers left knee that can get full of lent and bias the climate control to not regulate properly

There is a control panel self test with codes of faults that someone has made a Youtube video of the X300 almost the exact same X308 system , this test does not see everything like a dirty cabin temp sensor and core clogging but I can tell the document was made for the X308

See page 110

T703 BOOK

Codes are here :

Coming

 

Couldn't find the X308 codes but this is the almost exact same X300 Denso manufacture system on the X300 / X308

14-10

 

This is why it’s important to turn the heater on full blast a handful of times during the offseason. Albeit you can’t prevent a pump or valve failure, you can at least help keep the minerals from sitting stagnant. Using distilled water instead of tap water also helps reduce minerals in the system. Eliot, flushing out the heater core in both directions is the way to do it. I would use white vinegar vs CLR as it’s cheaper and it’s just as affective.
my 2¢.

 

Damn those christian sensors giving up heat for lent

More seriously, I back flush in both directions too. It stirs stuff up & seems to get more out. I did mine when I changed the coolant the other year, I didn't have any issues but it seemed daft not to do it while I had the system empty. I did the same to the block, intercoolers & rad too.

 

I thank everyone for their tuppence of advice and links. I took the beast for a run today to band practice an hour away. After 45 minutes I stopped and checked the driver’s footwell outlet in full heat position. It was a mere 122F, and the top outlets were about the same. I knew I bought a digital meat thermometer for a reason!

However, on the drive back … when set for a lower temperature and a higher one was demanded, there was no rush of pleasantly warm air. When I got home I did set the system on manual, Hi heat, engine on,, and felt the pump. It felt as if it were running and the output hose felt warm.

What I have learned here (thank you everyone) is the actual location of the heater hoses: below and slightly to left of the coolant reservoir looking from the front of the car to the firewall. And the reservoir can be moved a bit for better access to the hoses. I see the heater core input hose runs from the firewall to the side of the aux pump. The output side goes heaven knows where but it should be traceable. I’m not sure I have either the time or talent to do this myself, but I now know enough to see if I can take a stab at it and, if it drives me nuts, button it up and take it to my Indy garage with specific instructions on what to do.

Question: This might be easier for me to take on if I knew the inside diameter of the in/out hoses or the pipes at the firewall so I could just disconnect the hoses, run to a parts store for some longish plastic hose that would fit into each in/out pipe or hose, then proceed with the flushing operation. That still won’t help me know if the pump works, though I suspect I could turn the heat on and see if it expels some water from the output side.

Again, thanks to all who have chimed in. And, yes, giving up heat for Lent is a very uncharitable thing to do!

 

5/8" heater hoses but you don't need a lot of flow or pressure for this operation. My cheap chinese little electric transfer pump has 3/8" hose barbs so I used the 3/8" hose I already had and ordered some cheap, plastic 3/8" <> 5/8" hose barb adapters off amazon.

 

Another bit of info is this…. Just because you can hear and feel the pump running does not mean it’s pumping. Huh? The actual pump impeller is not physically connected to the electric motor as it is driven off of magnets. If there’s still blockage inside the heater core, then it’s likely the impeller is sitting relatively still even though the pump is operating.

 

Thanks A2B, I recall that from rebuilding one either in my XJ40 but more likely in my X300L. I found brushes at a hobby shop, filed them down, and presto chango, it worked.

 

with a 122 F output air it does prove the pump motor is turning ( and magnetic driven impellor somewhat ) and the coolant solenoid valve is modulating open closed

So that leaves the question of heater core blockage

Self test codes ?

Cabin temp sensor clean of lent ? this require removing it from the backside of the large kicker panel below the steering wheel , use no solvent

Someone has a great pic of this sensor and back of panel

Before digging too deep are both cabin blowers working by fuse X and Y for total cabin warm up feel as a whole ?

This is a pic of a very much same X300 system ( yep , the arrow is not pointing to right thing )

 

Today is spoken for. I expect Monday will be sensor cleaning, code-checking day. Thanks.

 

Cabin blowers fuses :

# 11 left heelboard fuse box and # 11 right heelboard fuse box big power to blowers

and # 12 left heelboard fuse box ( you should have this as both cabin blowers relay " control " power as you have at least some cabin blower )

 

Thanks for adding to my store of knowfedge. Heaven knows i need all that can be imparted. Fortunately the blowers both work fine as do the blend flaps. I think there’s a fuse in the right heelboard for the auxiliary pump, I have a vague sense maybe #7. Monday and Wednesday are good days for me to goof around and at things. I did find the interior air sensor today behind and above the change cubby on the left side. I’m not big on laying upside down to take out screws I can barely reach so I just summoned up a deep breath and blew like crazy into the device! If I took down the entire bolster under the steering wheel it would be easier, but at the moment it’s not as suspect as the heater core.

 

coolant heat auxiliary pump fuse # 15 / 10 amp engine compartment fuse box

Relay # 1 engine compartment fuse box , you can put your finger on the relay and feel for click closed




See page 77

note the ground wire terminal can be cleaned with a wire brush and light bulb grease ( in the small packets at the auto parts store counter ) to preserve

X300 01/E COVER