Hey guys,

as we have had temperatures well below the freezing point (-10°C to -15°C), I have noticed that my heating seems very "meh", that is the best way to put it. It works, so the heater valve works, as I get some heat out, but I don't really get much heat.

What function does the heater pump have? Is that to help with the engine water pump cycle the water through the heater core or is that a different matter?

My water pump will be replaced soon, once the replacement is here. My brain is telling me, that the water pump isn't pumping enough (the fan cut in a few days ago after parking the car with a normal drive, at -12°C that day it seems a little "cold" for that...). 21 years in the car probably would justify a new pump. Especially since the fan would cut in in summer all the time. The thermostat is basically new. But will also be replaced.

Does that make sense to you guys? Water pump not pumping right (spinning impeller on shaft or better said not spinning impeller) causing the heater not to get enough water pumped through? The engine temperature is always reached within a few kilometers, even at -15°C. The upper hose is hot, so the thermostat opens...

Otherwise any ideas or is the X308 heating "meh" from the factory? The XJ-S V12 heated like a central heating boiler... So Jaguar knows how to make a heater

Cheers

Damien

 

The most likely culprit is the heater pump. It may have a blown fuse and not running or it may need replacement.
Take a read thru the thread below.

https://www.jaguarforums.com/forum/x...o-heat-152065/

 

Do I assume right, that applying 12V direct to the pump and seeing if it makes a noise should indicate a functioning of it?

If the pump is dead, shouldn't there be no heat at all? I have some heat and it does heat up but it isn't a high intensity... It doesn't heat to the degree I would expect it to.

 

Hit the heater pump with a broom handle and you might get the brushes to move down to make contact ( for a while ) . If you are over 100 k miles consider replacing the brushes . At high RPM the engine will feed the heater matrix but then there is a check valve the X300 does not have . Feel for the relay to click when commanded on . The flow valve does not have a relay

 

Jaguar addressed this 20 years ago.
When I flush the heater matrix, I 'pinch' and disconnect the hoses from it to attach clear poly hoses and JUST clean the matrix.

Gently blow compressed air to clear the fluid and then add some cooling system flushing compound. Let it sit overnight and then flush out the core.

Attach the hoses and see if the heater performance has improved.

I have done this when these cars were still in factory warranty. Almost always improves the heater if all else is operating properly.

bob

 

 

General first rules:
-if you got some heat on idle, but little on speed: heater core,
-if you got some heat at speed, but little at idle: heater pump,
-if you only got heat at full temp setting: interior sensor.

 

And if you have heat all over the range but it is all low? No matter if high RPM or low RPM?

 

Something is scavenging, either heater pump or water pump.

check the engine waterpump - if it's the black impeller then this is the likely weak heat cause a well known issue on the earlier cars, I'd be surprised if it was still in there, it led to a few dead engines (overheat events and dropped valve seats).

Have you confirmed if the heater pump/valve are working?

You want the heater loop 100% - use a radflush as Bob as suggested. Check all the parts in the loop and then post back findings. Plenty of good info already suggested.

 

As said, I will be changing the water pump, as I suspect it not to be working properly. Also, I bought the car with a full dealer service history. Yes, it looked very tatty as I got it but the mechanicals were to a rather high standard just the owner had lost interest in keeping the car and investing in it...

In all the papers, not once is the water pump mentioned. The power steering pump was replaced 3 years after leaving the factory in 1997, the intake manifold was replaced due to two faulty injectors in 2001. But nowhere is the water pump mentioned. So it has had a few things replaced but just like the tensioners, some things hadn't.

I just remembered, that I had some pictures of the water pump, as I replaced my tensioners and co. The water pump has the following number in it:

2W93-8501-BC



Google says it is a Land Rover part!? Although that might just be a crossreference, as other used waterpumps from early X308 and X100 models had the same number on them... At least by eBay and co. Very mysterious.

As said, I have noticed that my fan runs after the car is switched off nearly all the time. The thermostat is fine. But then, if the thermostat was dead, I would be getting a lot more heat inside the car... Or maybe the thermostat has died open for a change!?

I'll see next weekend when the new metal impeller waterpump arrives. Can't go a miss changing the water pump anyway.

 

If your fans are running full speed after a drive when you stop (and engine idles) or after you have switched it off, in so cold weather you have there, it looks very much like the water pump. You can verify this if you check the temperature of the radiator while the fans are running, it is probably "cool". I had similar problem on my Daimler Super V8 when I bought it. Not in cold weather but my fans would go to full speed after a short gentle drive (when they shouldn't really, perhaps low speed only) and run for quite some time after the engine switch off. When I removed the thermostat cover - there was no thermostat!? So, the flow through the radiator was probably only half of what it should be and the other hot half was going back into the engine without being cooled. On your engine, when you replace the pump it is probably a good idea to also replace the thermostat. I have read that the thermostats on these engines should be replaced every couple of years (perhaps only on supercharged, cannot remember now).

 

Yeah, I woud understand the fan to cut in after a hard thrash... As I replaced my thermostat tower, I replaced the thermostat. As the upper hose is hot though, it is opening, but I'll still be replacing it.

I know the temperature gauge isn't there for showing the temperature properly. It is just an idiot gauge BUT mine will sit regularly above the "normal" position. Cold starts obviously not. It has already before gone up before the red - as the thermostat was dead...

As already written, the pump is getting replaced.

 

The early cars had all kinds of cooling issues -- bad pumps/ clogged matrix/ two different fluids (incompatible). My 98 VDP had the WP upgraded as a precaution and the dealer went to great lengths to make sure everything was properly flushed. I'm sure procedure above from Bob ... you can see by the complexity of the TSB that this was not going to be followed if not under warranty and done by an outside garage.

My memory was Jaguar changed the fluid twice before the Orange. I can't remember ... I think my X300 was blue .. they went with a yellow at some point and finally the orange. My 98 was totaled and I bought the 02 ... so my problem went away. I also remember lots of early cars in for service having low heater output ... the incompatible fluids took a toll --- gummed everything up. Overheated engines. Bob can confirm ... I thought Jaguar upgraded the matrix ... maybe this was from the X300 to x308?

 

I just installed a digital temp gauge. Did not want to cut any holes anywhere so I found a good place, easy to see through the steering wheel. It shows ambient temperature in Celsius, slightly warmer than Europe at the moment.

 

After replacing my water pump yesterday, I can confirm the original plastic pump worked fine WHEN cold. The coolant from the last 21 years haven't left any traces inside the engine. So no deposits. I DOUBT the heater core is blocked. This is thr first time that I have ever seen such a clean cooling system in a Jag. Bei it my V12, my former 3.2l AJ16, my friend's 4.0l AJ27 or any of those many V8s where I replaced the camchains...

Once my new belt tensioner arrives, I'll be able to check for the heater pump.

Is it worth replacing it with a used part or are there any aftermarket parts you can rely on?

 

Used should be fine, I'd check the condition of the brushes in the replacement motor. I've been having the same issue this winter, poor heating with an occasional complete loss of heating, once up to operating temp. Not affected by driving speed. I'm suspecting the heater pump, so I've got a used unit awaiting brush replacement so I can just replace the pump in my car with the repaired pump and not risk being out a car if something goes wrong.