I'm having trouble with my heater when first started and it's cold outside when I turn my heater on it causes the windshield to frost over but when traveling and the engine is warm and running above 2000 rpms I get hot air but lose it soon as I stop or even let off the gas and let the rpms drop what is causing this

 

If your vehicle has an auxillary electric coolant pump for
the heater, look at that as the first item. They are meant
to provide sufficient coolant flow to the heater core when
the engine is idling.

If not, then look at the engine water pump. The impellers
may have shredded.

 

There are a few checks you need to make.
1. Is the coolant full.
2. With the engine warm and at idle are the heater hoses warm like the radiator hoses. Both the inlet and outlet.
I have added a link to a post where we have dealt with this recently.
There is a lot of good information about all of the possibilities for the condition you are experiencing.

Let us know what you find and we can proceed from there.

https://www.jaguarforums.com/forum/x...-vents-154169/

 

Thank you and about the water pump if the impellers have shredded would it be leaking coolant because It doesn't

 

I usually see this when coolant levels are low. I wouldnt think water pump as you dont seem to have any overheating issues.

 

Bryan,

I think the Water pump is shot..But I know someone who is a Master Jaguar tech and has a shop in Moore off of I-35..he's reasonable and expert...give me a PM and I'll hook you up with him. If you want to have it looked at or fixed...His name is Bryan too.


Don't drive it much in stop and go traffic..I have a feeling you do not have proper coolant flow.

 

I had this issue and it turned out that the coolant was low. Reminder that I needed to flush and refill it anyway!

 

I would like to thank everyone for your opinions each one was taken into consideration. And as for my coolant levels it was low but even will topped off same stuff. Iv been fighting a constant battle with the cooling system ever since I blow a thermostat back in June I'll fix one thing and another thing breaks it seems like and DPK imma take you up on that offer I'll be getting in contact with you for the info and once again thank you everyone for the help but it's time to get this under wrap tired of throwing money into it I'll keep everyone posted on what I figure out about the problems I'm having vroom vroom jag lovers

 

Hey, um, I'm now experiencing this too. I don't seem to have overheating issues. I've driven in stop and go traffic. I had the oil changed and they topped off the fluids and nothing seemed out of sorts except the a/c compressor leak I have (still haven't fixed). I'll check the coolant again, but wouldn't the jag run abnormally if the water pump went out? Wouldn't my temp gauge show it running hot? I assumed it was my A/C compressor, but then questioned whether it was logical for the issue to be connected and decided to check on here. Viola! There's always a thread

 

The Jag engineers seem to favor the approach of a High Velocity/ Low Capacity cooling system for our cars. There are 4 major reasons for loss of heat at idle.
1. Low coolant. You stated they topped off the fluids at the oil change. Was the coolant low?
2. Air bubble trapped in the heater core. Can be caused by topping off with engine not running.
3. Worn pump impeller blades. Most likely cause if coolant level is consistent.
4. Stuck blend door on the air unit under the dash.

Check out the thread posted earlier in the this thread and you will find ways of dealing with each of the 4 problem areas.