13 replies to this topic

[lippo]

 Hi, I have just performed a radiator flush as over the weekend, when the mini was in stationary traffic, the needle started to creep up to the red.

 

 I've followed the helpful suggestions already posted on the forum. I flushed through with Holts Radflush (didn't like the sound of the CLR stuff) and the rad was reasonably clean. I could only drop around 2 litres of water, and I think the total coolant capacity is nearer 4 litres.

 

 I noticed that the heater matrix wasn't getting hot at all, and the pipes in the engine bay were cool. I disconnected them and flushed them with a garden hose, both ways. A fair amount of fine sediment was removed, and the heater matrix wasn't allowed to run dry. The garden hose passed water through fine, although the flow rate wasn't great - it was more than a trickle, less than a torrent! I ran the water through for quite some time and it was clear for pretty much all of this period.

 

 I have re-connected everything and the heater is still cold. I have checked the heater valve on the cylinder head - it doesn't appear blocked and I've put a screwdriver down there to make sure it isn't wedged shut.

 

  All the pipes seem in good condition, some of them renewed within the last few years. At least the Mini doesn't overheat when idling now, but I would like to get this working properly.

 

 Is it best to replace the heater matrix due to the average flow? Remove and try to clean it that way? Should I replace the heater valve too?

Edited by lippo, 19 May 2025 - 04:34 PM.

[bpirie1000]

Would certainly consider a chemical flush or if possible take radiator out and check individual components.

Also maybe consider thermostat change...

May also consider the temp sensor change... just to make sure the sender is not faulty....

Interir heater matrix are also usually an issue can flush them independently just be methodical..

[Quinlan minor]

I’d suggest bleeding any air out of the pipes to the heater.
It may simply be airlocked.

[lippo]

Would certainly consider a chemical flush or if possible take radiator out and check individual components.

Also maybe consider thermostat change...

May also consider the temp sensor change... just to make sure the sender is not faulty....

Interir heater matrix are also usually an issue can flush them independently just be methodical..

 

 I think I'll have to take it out and get a proper look. The water does flow through the pipes/matrix so I'm confused why there's no hot water getting through. I've had the thermostat out last week, and it does hold temp at normal running - it also holds temp better after the rad flush. I feel the temp sender unit is working correctly too.

 

I’d suggest bleeding any air out of the pipes to the heater.
It may simply be airlocked.

 

 I flushed it with the garden hose for quite a while, I'm confident there's no air in there.

[Steve220]

Did you reverse flush it?

[Kevybmini]

Hi,

 

I had all the same problems, changed the heater matrix for one of these and all is well. £90 but is a proper copper radiator not a rubbish pressed aluminium one. 

 

 

https://thecarheater...x-1984-to-1992/

[lippo]

Did you reverse flush it?

 I did, yes. Fine, dark sediment came out during both flows of flushing.

[Kevybmini]

The two pipes to the heater matrix should both be hot - if not it’s block or restricted flow inside 

[lippo]

Hi,

 

I had all the same problems, changed the heater matrix for one of these and all is well. £90 but is a proper copper radiator not a rubbish pressed aluminium one. 

 

 

https://thecarheater...x-1984-to-1992/

https://thecarheater...prated-version/

 

 That would fit mine. I would consider it, but in the first instance I'm not looking for a performance enhancement, just something that allows the hot water to flow through correctly. 

[lippo]

The two pipes to the heater matrix should both be hot - if not it’s block or restricted flow inside 

 They are stone cold. Matrix is cold too, which I find strange as I flushed it thoroughly. I wasn't impressed with the flow rate, and think that the blockage is too much for the pressure in the cooling system to overcome. I just wasn't sure how well the matrix flows in the first place.

Edited by lippo, 19 May 2025 - 08:19 PM.

[lippo]

I've removed the heater, turns out the newish pipe to the heater valve was blocked with crud from the heater matrix.

 

All cleaned and matrix properly flushed through then topped up with de-ionised water. Bluecol used 50/50 with the de-ionised water to fill the radiator. I could still only get around 2.5 litres in there in total, I guess there's a lot of water in the block that's difficult to drain.

 

 The car is getting to temp and staying there, the heater is hot to the touch, and no overheating whilst idling.

[mullet]

I've removed the heater, turns out the newish pipe to the heater valve was blocked with crud from the heater matrix.

 

All cleaned and matrix properly flushed through then topped up with de-ionised water. Bluecol used 50/50 with the de-ionised water to fill the radiator. I could still only get around 2.5 litres in there in total, I guess there's a lot of water in the block that's difficult to drain.

 

 The car is getting to temp and staying there, the heater is hot to the touch, and no overheating whilst idling.

As we have discussed on another thread, yesterday I got the heater out of the car and flushed it.  I put it back in, but empty of water.  Should I try filling it at the higher inlet as much as possible?  Or will air find its way out again when the entire system is refilled?

[Quinlan minor]

In my experience, it's best to fill from the highest point with the heat control "On", to avoid airlocks.

[lippo]

 

I've removed the heater, turns out the newish pipe to the heater valve was blocked with crud from the heater matrix.

 

All cleaned and matrix properly flushed through then topped up with de-ionised water. Bluecol used 50/50 with the de-ionised water to fill the radiator. I could still only get around 2.5 litres in there in total, I guess there's a lot of water in the block that's difficult to drain.

 

 The car is getting to temp and staying there, the heater is hot to the touch, and no overheating whilst idling.

As we have discussed on another thread, yesterday I got the heater out of the car and flushed it.  I put it back in, but empty of water.  Should I try filling it at the higher inlet as much as possible?  Or will air find its way out again when the entire system is refilled?

 

 Yes, I filled mine with de-ionised water prior to connecting it back up to the head/upper rad hose. Saves any issues further down the line with air pockets.