Heater

[svenedin]

Relativley new to Moggys 12 months, My 69 Moggy has never really been warm, so a bit of a refurb was in order, New Rad, More efficient water pump, new diverter valve and 88 deg Thermo. flushed the matrix all good, Still doesnt get warm , thinking of lighting a fire. any ideas

You mean the heater doesn't get warm? The heater box has a "matrix" inside it which is basically a small radiator. It is often totally or partially blocked with rust and sludge. Another possibility is that the heater tap on the cylinder head is not opening properly. Occasionally the problem is poor water flow to the back of the engine again due to sludge.

First check the heater control is working. Push the heater knob under the dashboard forwards. Check the cable has pushed forwards the plunger of the cable operated valve. Or if the earlier brass stopcock type has been fitted check this is open.

If that didn't help.......Drain the coolant. Open the engine block drain (on early engines this is a brass tap, on later engines this is a hex drain plug). Disconnect the heater return rubber pipe (this is the pipe that joins the metal pipe that runs front to back of the engine and joins the bottom radiator hose near the water pump). Disconnect the heater flow pipe from the heater tap and direct it into a bucket. Now connect a garden hose to the heater return pipe and force water through the heater matrix. The heater pipe is the same inside diameter as garden hosepipe. Flush until the water runs clear. Now connect the hose pipe to the heater tap, ensure the tap is open and force water through that. Water should flow out of the engine block drain. Reconnect everything, refill with coolant and hopefully you will have a warm heater.

Warnings before flushing: if your heater hoses are in poor condition or the heater matrix is very rusty, flushing it may cause it to leak. Have some old towels at the ready just in case.

Stephen

[SALFORD6]

Yes its the heater that isn't getting warm, l have replaced with new all the relevant parts , and flushed the matrix, it's like the hot water isn't getting to the matrix, bottom hose is hot but before it gets to the heater its cool, So may have to drain and flush the whole system. David

[SALFORD6]

I could short circuit the water supply to the heater by connecting a tube to the in and out and see if it gets hot, this will rule in or out the matrix. David

[Bill_qaz]

With the heater valve open is the hose coming from it getting hot to the touch?
If so is the return hose also getting warm?

[svenedin]

Yes its the heater that isn't getting warm, l have replaced with new all the relevant parts , and flushed the matrix, it's like the hot water isn't getting to the matrix, bottom hose is hot but before it gets to the heater its cool, So may have to drain and flush the whole system. David

Ok so if the heater tap is definitely open and you have flushed so the matrix is clear it must be that the circulation of water is poor at the back of the engine. I am assuming that if you attach a hose to the heater flow pipe that water flows out of the return pipe at this stage.

Yes, try a flush of the block (since you already have a new radiator). Remove block drain and flush by attaching a garden hose to the heater tap. If as I strongly suspect, no water comes out of the engine block drain you are going to have to have a poke around in there with some stiff wire (coat hanger wire). Many forum posts about doing this. You can also try using citric acid in the coolant and running the engine up to temperature several times over a few days and then a thorough flush. You can buy citric acid cheaply as crystals and it is used as an appliance descaler (kettles, washing machines etc). Dissolve about a cup of crystals in hot water and add to the coolant. There is no point adding citric acid to the coolant without running the engine up to temperature. The descaling is very slow when cold and with no water pump running it can't circulate. If crud is the only thing keeping water in your cooling system dissolving the crud may cause leaks!

Stephen

[Bill_qaz]

If the supply hose to the heater is getting hot it must have flow to it. As I asked is the return hose getting hot, the one that returns to the bottom radiator hose. If not slacken the hose from the heater and see if hot water is coming out?
Stephen if the block was corroded that badly how is it getting flow via the heater valve and heating the hose to the heater?

[svenedin]

If the supply hose to the heater is getting hot it must have flow to it. As I asked is the return hose getting hot, the one that returns to the bottom radiator hose. If not slacken the hose from the heater and see if hot water is coming out?
Stephen if the block was corroded that badly how is it getting flow via the heater valve and heating the hose to the heater?

I didn't think there was flow via the heater valve.....

Stephen

[Bill_qaz]

I thought when op said bottom hose was warm I thought he meant bottom hose of the heater which is input. If he meant bottom hose of the radiator then thats the heater return.
We need to clarify which pipes are getting warm or remove heater hose from tap when closed then block pipe, open heater valve with engine running and check if flowing or blocked as you suggested.
When recently changing my heater control valve, when the hose was removed I got flow even with engine stopped as its lower than the radiator header.

[jaekl]

Are you sure the heater is filled with water?