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2006-2009 Range Rover Sport
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535 Posts
Discussion Starter #1
So I installed the Audi heater core and new core heat sensor on the weekend. Before I put everything back together I fired her up and got it to temp, checked for leaks and heat. It was 0 deg C and it felt like it was blowing heat so I shut her down and put everything back together. So here I am at -25 Deg C and I am getting heat but not enough. Feels luke warm.
I have no Error displayed on HEVAC screen and all blend, recirc motors operate correctly. The connections on the heater core were connected to the correct connections at motor. Top pipe on core is supply and bottom is return as the core showed on the connections with little arrows. I installed the sensor on the top pipe. I could not find a 5/8 to 3/4 plastic adapter and had to make the connections in the engine bay with brass fittings. Because of this the internal diameter in the 5/8 hose is reduced quite a bit. Would this prevent the core from getting enough flow, hence my lack of heat? Should I reverse the pipes and get it a go? Please help me I'm cold!!!! Thanks!
 

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1970-1995 Range Rover Classic
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2,032 Posts
did you bleed the system properly? if, not you have an air bubble keeping the fluid from going through the heater core.
 

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2006-2009 Range Rover Sport
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535 Posts
Discussion Starter #3
I will bleed the system tonight. I am also trying to locate plastic couplers for the piping as I am not happy with the internal diameter of the brass fittings. It reduces the pipes to 1/2" or less.
 

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2006-2009 Range Rover Sport
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535 Posts
Discussion Starter #4
I changed the brass fittings to a larger inside diameter plastic fitting. I then jacked up front corner of truck and bled the system. Still no real heat! Took the truck for a spirited drive and boom I had full heat again. Started the truck a few hours later and I had heat at idle when engine hit operating temp! Solved!
 

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1995-2002 Range Rover P38A
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176 Posts
when you put everything back together - did you inadvertently crimp or pull a joint too tight? I know that my transitions under the hood had some tight spots until I moved my joints and changed my plumbing :)
 

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Have you noticed any change in the resevoir level after that run which would indicate that you had an air pocket. Sudbury can certainly get brisk so good to hear you got it sorted and the audi core works as I'm sure ours will come due
 

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2006-2009 Range Rover Sport
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535 Posts
Discussion Starter #7
when you put everything back together - did you inadvertently crimp or pull a joint too tight? I know that my transitions under the hood had some tight spots until I moved my joints and changed my plumbing :)
I replace original hoses from motor and with the new connectors the flow increased to almost OEM diameter. I think this was the issue.
 

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2006-2009 Range Rover Sport
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Discussion Starter #8
Have you noticed any change in the resevoir level after that run which would indicate that you had an air pocket. Sudbury can certainly get brisk so good to hear you got it sorted and the audi core works as I'm sure ours will come due
I was waiting to check it when cold which I did not get a chance yet. I suspect it will have dropped. I had no change in heat until the RPM hit 3000rpm. Then it must have dislodged the air.
 

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2006-2009 Range Rover Sport
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535 Posts
Discussion Starter #9
So here I am a week later and I still have luke warm heat. No other issues.
On the Audi heater core the coonections when fitted in the P38 are Top = Supply and Bottom = Return As seen in this picture. $(KGrHqRHJE0FDdKielblBQ8-MpVylw~~60_1.jpg

On the original Core the connections are as shown in this picture: Photo credit to heater core replacement FAQ on this site.

heater02.jpg

Should I reverse the pipes on the audi core as it looks like the core is getting fed to the top rather than the bottom like the original core.
 

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Administrator
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27,802 Posts
That's like asking which way a straw should shuold go into a milkshake. It works the same no matter which way the water flows. The only concern with keeping top and bottom on the original core is proper fitment of the pipes. HOWEVER the slight difference for the heater core temp sensor MIGHT make a difference. Of course now that I say that I can't remember if the sensor clips to the inlet or outlet pipe. :-?
 

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2006-2009 Range Rover Sport
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535 Posts
Discussion Starter #11
If I was installing an original core to the truck your straws in milkshake theory would be correct as the fluid enters via one port and does not mix with anything and then exits.
These Audi A4 cores however just have a tank on one side so they depend on heat transfer within the core as the fluid mixes internally.
I can't remember which pipe the sensor was on either. I did clip it to the top pipe on reinstall.
 

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2006-2009 Range Rover Sport
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535 Posts
Discussion Starter #12
Here is a sketch I did showing what I think is the differene between the original, audi installation and p38 installation.
Core.JPG
 

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With something as small as the heater core I simply don't see it making any difference which way it flows. It's not like the added work a water pump has of pumping radiator flow bottom to top instead of flowing top to bottom on some cars. Hopefully Scotty and/or Martin will have an idea since they have dome this changeover.
 

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Those plastic tanked repro ebay Audi heater cores are junk, I had one split open after a month and shower my daughters leg with hot coolant.

Do yourself a favour and get a more durable copper one.
 

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2006-2009 Range Rover Sport
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535 Posts
Discussion Starter #15
Good to know! I've been into the dash 3 times now I think I could set a record for a core replacement lol!
Which pipe did you connect to which pipe on the core?
Also which pipe did you put the sensor on?
 

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LEGACY VENDOR
1995-2002 Range Rover P38A
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4,218 Posts
I've just had a look at the pictures I took from when I did the install in my RR..

I plumbed in the bottom connector as the input, and the top one as the output. I haven't had any issues with it (other than the hose clamps loosening over time) and it gets plenty warm.

I also put the heater temp sensor on the input pipe, as I figured it was better for the HEVAC to measure the heat on the input side, rather than the output, which would be cooler than the input, after having the air flow through it in the heater box.

I don't think it matters too much which is which as the coolant tank/top of radiator is higher than both of those pipe connections in the P38, so (in theory) the air will be pushed out as the system gets filled..

Cheers,
Marty
 

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2006-2009 Range Rover Sport
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535 Posts
Discussion Starter #17
Well I went back in under the dash and swapped the pipes. The supply is now connected to the bottom pipe and return out of the top. I put the sensor on the bottom supply pipe. Heat is now fully functional.
 

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1970-1995 Range Rover Classic
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2,032 Posts
good to know. i'm going to do this swap once the weather warms up. its too cold to rip the dash out.
 

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2006-2009 Range Rover Sport
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535 Posts
Discussion Starter #19
So I have air in my coolant system and have tried to bleed it several times. It is currently -27 Deg C (-42 Deg C with wind chill) outside.
I disconnected the small pipe from the rad and blew all the coolant from the line. Took res cap off. I jacked up the front and ran the motor at 2k rpm etc... everything Rave told me to do. But I am getting an air pocket on the return from the heater core. I checked the temp of all the pipes with IR temp gauge. Supply to core is 80 Deg C and return is 41 Deg C. If I rev the motor the temp on the return increases and the heater works. But once the motor returns to idle the temp of the return drops.
When I rev the motor I do get a burp or 2 of air in the reservior so there is air in there coming from somewhere. The top rad pipe is 80 Deg C and not hard. I measured the top of the Rad and it was 80 Deg C where the pipe enters and 50 Deg c on the oposite side. I have no overheat issues or coolant loss unless it is evaping on the exaust manifolds.
I have previously pressure tested to 18 PSI and found no leaks other than a loose clamp on the rad top hose which I tightened. Any ideas?
 

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JACK'S GRANDAD
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9,242 Posts
You are replacing the cap when trying for heat arent you?
O rings on the cap look good?
I posted how I bleed the P38's I work on before, and got moaned at about my way of doing it. Works ever time though, for others too apparently...
Will shoot you a PM with a good (IMHO) way of doing it, then I save myself from being whined at again for thinking outside the box.

Martin
 
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