Heater woes ....

[Hargo]

Afteroon all,

Ever since I got the 350 a month or so ago it's been running very cool ( 65 - 75 degrees on the motorway ). The previous owner had just fitted a new radiator and water pump.

The heater is also luke warm at best.

So yesterday I flushed out the cooling system, fitted a new 82c 'stat and flushed out the heater both ways ( which flowed fine ).

After all of that it still runs cool and the heater is luke warm. So I topped up ( and kept an eye on ) the coolant, ran the engine and disconnected the driver's side heater pipe from the back of the engine which I believe to be the return. No water was coming out at all even with 2000 - 3000 revs. Re connected that, disconnected the other heater pipe and water came out of the metal pipe on the engine. So it appears that water is being pumped into the heater but not getting through it which would possibly explain why it is luke warm and gets colder if the fan is on ( i.e acting like a small radiator )

Has anybody got any ideas why this is happening and if so how to fix it ?

The pressure of the water coming out of the passenger side pipe was alright, it wasn't just a trickle, unless they need a lot of pressure ....... ?


Thanks in advance !!

Al.

[degz]

Not taking the Pi22, but you have checked the cable is doing its job of turning the heater on and off? the tap may have stuck in the nearly closed position.

[KJR]

You also need to check that the levers on the dash are labeled correctly, I know that on my 1989 400se they are labeled the wrong way round.

The dashboard lever labeled "Cold/Hot" actually adjusts the direction (Screen/Feet) and vic versa for the other dashboard lever.

Only took me eight years to work this out .

Kenneth.

[arcturus]

degz said:

..but you have checked the cable is doing its job of turning the heater on and off? the tap may have stuck in the nearly closed position.

Hargo said:

..and flushed out the heater both ways ( which flowed fine )

Does this not indicate that the tap is open or am I missing something?

Not trying to be clever, just curious as I have exactly the same symptoms as Hargo, except mine does run at a normal temp according to the gauge.

[chunder]

arcturus said:

degz said: ..but you have checked the cable is doing its job of turning the heater on and off? the tap may have stuck in the nearly closed position. Hargo said: ..and flushed out the heater both ways ( which flowed fine ) Does this not indicate that the tap is open or am I missing something? Not trying to be clever, just curious as I have exactly the same symptoms as Hargo, except mine does run at a normal temp according to the gauge.

The tap referred to is a valve that opens and closes on a sliding lever operated by a wire that runs to the hot/cold slider control on the dash. The valve is (normally) under the bonnet on one of the two heater hoses. If this is open and no flow then it sounds like the heaters getting airlocked (search previous threads for cures to this). Try and find where air is getting in (do you have a small coolant leak anywhere ?) or try topping up the coolant system from the top heater hose.

[Hargo]

Thanks for the replies !

As far as I can tell there isn't a heater tap fitted. At least I can't find one, it's not in the engine bay and not under the dash near the ECU & wiper motor. Plus water runs through fine with a hose in either direction.

From what I can tell the coolant runs through the heater matrix constantly ( or rather it's supposed to ) and the rotating temperature control opens a flap to let air from the fan throught the matrix or not depending on the position

Moving the temp control from hot to cold does change the air temp from luke warm to cold.

I've tried both controls in all postions but they seem to be labelled correctly, unfortunately ....


I think / hope that it is an airlock and I'll try what jmorgan has suggested in previous threads about fitting a bleed valve to the heater pipe. Does anybody know which pipe would be the best to fit it to, inlet or outlet ?

Thanks again

Al.

[jmorgan]

I put my valve in the highest pipe. Not sure if it was go or return but seemed the most likley to clear air locks.

[Hargo]

Thanks Jeff, was just about to email you.

Mine has a pipe coming through the bulkhead on the passenger side and a pipe coming up from the gearbox area on the diver's side ( which I think is the return ). Come to think of it, if that pipe goes down then up into the cabin / heater matrix, then there's a good chance that there is an airlock in it !

I'll put it in the passenger side pipe as thats the highest one.

Hopefully that'll solve the problem .......

Cheers

Al.

[jchase]

Hi Al (et al )

My 1987 350i has a similar set-up; no heater valve, just a flap in the box. I too have the choice of luke warm or cold. I presume there must be an oriface in the matrix circuit to regulate the coolant flow through it ?

The Previous Owner had fitted an extra temperature sender in the matrix delivery pipe - odd place to put it, but I noticed my main gauge runs at 90c spot on while cruising, and the matrix gauge starts off at 80c, and then drops to about 50c after an hours driving.

I tried a matrix back flush, and an air bleed - all to no avail - the choices remain luke warm or cold.

I guess a clever thing to do would be to fit an electric pump in to feed the matrix - the more heat you want the faster the pump goes - then you wouldn't need the flap at all. There must be a car with this set-up somewhere in a scrappy that we could find...

-Jim