9 replies to this topic

[liam1288]

hi guys, i recently had a split hose on a drive so all my coolant was lost... replaced the hose, coolant and bled the system until the heater was blowing hot (took a few times to get the air out) all the hoses were getting hot to touch.

so it was blowing hot while i had it on idle... i thought id go for a test drive to confirm...

basically now, when at idle the heater blows cool air but while revving or fast idle i get hot air out.

 

could it be more air in the system? 

an obstruction on the hoses? 

weak water pump? (there does appear to be a slight whine from the pump area, though not sure its the pump. it does increase with revs though)

 

ill check the belt and keep at bleeding tomorrow but whats the best way to flush the system? 

thanks

[Ben_O]

I would say more Air in the system

[Ellie]

Sounds like a water pump problem, maybe the fins have worn down a bit. So when the engine is at low revs the fan cools the stationary water. As soon as you increase the revs the water flow is re-established.

[liam1288]

That's what I thought to be honest. All the hoses are hot and the heater does blow really hot with the revs on... So with that I thought the air lock has gone
Plus I saw somewhere about the pump making a screaching noise to indicate either pump or belt...
Granted it's not a screaching noise but more of a whine but definitely from that area.

[liam1288]

Also what's the best way to flush the system??
Cheers

[grck1]

with car at idle and a mechanical fan you will struggle to get noticable heat output. just not enough thermal output at idle to overcome all the heat loss in the system. as it blows hot when revved /  driving then i wouldnt worry to much.

 

not just minis that suffer from this issue. had a mk2 golf that did the same thing when i younger. was a pain to demist it after steaming up lol

[sonikk4]

If the cooling system is in good condition and the engine at operating temperature you will get heat from the heater system at idle.

Now it could be there is still an air lock in the system so I would try that first as it's easiest to sort out. Rad cap off and run it up to temp, refit cap and see what happens. Try and squeeze the heater hoses while doing this. Another option is to take the heater hose off the heater valve and pour water into the hose. Reconnect and try again.

Now the pump could be an issue but screeching is normally associated with a slack fan belt or even water on the belt. It's also possible the bearing has failed or is failing in the pump but you will notice this by taking the belt off and seeing how the fan / pulley feels when you try and move it.

I replaced the pump off my 39 year old clubby this year and to be honest there was minimal wear on the vanes but slight play in the bearing. However it still worked fine and it was the original one to. ( very low mileage engine) It did get replaced with a higher capacity pump though while I had it all apart.

[liam1288]

yeah i remember a while ago when i used to drive it more often that i would get heat all the time at idle and whilst driving...

 

the belt tension is fine and its not a screeching, more of a slight whine to be honest

thanks

[KernowCooper]

If it was working before the hose split it points towards air in the system, remove the output hose from the heater matrix and allow water to flow through with the heater valve open and then reconnect, topping up as you work.

[jime17]

You might have a partial blockage in the pipes or matrix. The higher pressure when revs are up could be forcing enough water through to notice the difference.