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Old 31st October 2021, 16:56   #1
Firmus Piett
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Default Hot air fine when moving, but cool stationary?

Hi all.
Got a perplexing problem at moment, especially with winter coming.
I have a R75 Connie 2.5v6 petrol auto.
It's had a replacement stat a year ago, no leaks or drop in coolant level, but my mechanic fixed a leak from the short straight plastic pipe a few months ago.
I think he put some kind of rad fix solution in, which I wasn't happy about.
After that I had no hot air.
I asked him to flush out all the coolant and replace, and while at it flush out the matrix.
Since then coolant seems fine, no loss, and car runs fine, but hot air is fine when car is moving forward but as soon as you stop, (with engine running) the cabin air drops to just barely warm. Start moving forward and goes hot again???
When running the engine runs at around 81° which I know is a bit cool, but the hot air is fine when moving.
Air con was degassed and checked about six months ago.
Any ideas?
Thanks

Last edited by Firmus Piett; 31st October 2021 at 16:57.. Reason: Mistake
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Old 31st October 2021, 18:07   #2
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When you say " but hot air is fine when car is moving forward but as soon as you stop, (with engine running) the cabin air drops to just barely warm. Start moving forward and goes hot again??? "


I presume you have the heater fan running at a reasonable speed both when moving and when stationary ?
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Old 31st October 2021, 21:09   #3
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You have an airlock!!!
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Old 1st November 2021, 07:58   #4
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You have an airlock!!!


That's my first thought too. There's a specific procedure for refilling and bleeding the KV6. How handy are you with the spanners Darren?

Oh, and steer clear of that mechanic. Putting sealing potions in the coolant can, and has caused catastrophic long term problems.

Simon
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Old 3rd November 2021, 08:54   #5
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Quote:
Originally Posted by Ducati750cc View Post
When you say " but hot air is fine when car is moving forward but as soon as you stop, (with engine running) the cabin air drops to just barely warm. Start moving forward and goes hot again??? "


I presume you have the heater fan running at a reasonable speed both when moving and when stationary ?
Yes fan on same speed. 75% speed.
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Old 3rd November 2021, 08:57   #6
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That's my first thought too. There's a specific procedure for refilling and bleeding the KV6. How handy are you with the spanners Darren?

Oh, and steer clear of that mechanic. Putting sealing potions in the coolant can, and has caused catastrophic long term problems.

Simon
I'm quite handy.
What's annoying is I asked him to do a coolant system flush and refill, and and assume he would follow rover procedures.
Do I need to empty it again and refill, following rover kv6 procedures?
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Old 3rd November 2021, 08:57   #7
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You have an airlock!!!
Mmm, that's what I wondered.
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Old 3rd November 2021, 10:21   #8
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Do I need to empty it again and refill, following rover kv6 procedures?
That's what I would do Darren. I'd say there's a high chance of success. Here is the procedure.

Unfortunately garages are under pressure to work as quickly as possible so don't have the time to look through workshop manuals for any special requirements, particularly when those manuals were, as in MG Rover's case, on CD ROM.

Please keep us updated!

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Old 3rd November 2021, 13:41   #9
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People who are smarter and more experienced with the 75 than I say an airlock is the likely culprit. Who am I to argue with that? They're probably correct.

The one other thing that comes to mind, though, is the possibility that the heater core (matrix) may still be restricted with the remnants of the goop that was put in to fix the original leak. That stuff is just evil. Some heater cores have smaller passages than radiators. I'd be prepared for another flush - maybe even just the core through the heater hoses and with a cleaning agent or vinegar or something. If the drain/refill process doesn't do the job...

Good luck,
Glenn
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Old 3rd November 2021, 15:16   #10
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... the possibility that the heater core (matrix) may still be restricted with the remnants of the goop that was put in to fix the original leak. That stuff is just evil.
That's a good point Glenn particularly as there's evidence that the thermostat is also suffering from the effects of the "some kind of rad fix solution", probably K-Seal.
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... the engine runs at around 81° ...
Hmmm, that's around 10° too cool so your thermostat has probably been sealed in a partial or fully open position. Your going to need several flushes using a cleaning agent and another new thermostat which should all be at the garage's expense, not yours.

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