This article details the process of valve cleaning/flushing on a BMW E36 320i with climate control and air conditioning.
Symptoms: No hot air coming through vents inside car although car engine is at normal temperature and there are no air locks etc in cooling system.
After flushing the engine coolant system several times and bleeding it I still had no hot air coming through blowers. This started worrying me as I understand that it could be a number of things... head gasket problem, water pump not working properly, radiator leak, or thermostat etc...
After checking the obvious I gathered that I need help and signed on to Pelican Parts and asked for help. In my case I had to remove the valves and clean them.
Tools required: T27 Torx bit, flat head screw driver, WD40, water and hose pipe connected to water supply.
This is how it goes: This can be a bit messy as in lots of water spillage so be prepared. You don't have to drain the water out of the system but you can do if you wish.
First of all you need to disconnect the power and the three hoses that go to the valves. The single hose on the underside of the valve housing is for water inlet to the valves and the two hoses on the side of the valve housing are the ones that go to your heater core.
On the firewall of your car you will find three hoses, two inlet and one return.
The return pipe goes back to the engine and continues the water flow. The other two are the feed from the valves and these flow water through the heater core.
To make sure that the heater core isn't clogged up, remove the hose pipes that connect to the heater core and attach a water hose direct to one of the inlet pipes and flush the heater core. This will remove any build up of rubbish that may have accumulated over time.
We will assume that the heater core is fine and not clogged up so we can move on.
After disconnecting the three hoses attached to the valve unit and disconnecting the power cable you can remove it. To do this you need to hold the unit and twist it upwards. With a little force it should pull out of the rubber that holds it in place
The valve unit has 6 torque splits on the underside, these need to be removed. Once removed carefully pull the valve metal casing away from the housing along with the plastic connecter for the power cables. You need to be very careful when doing this as you don't want to damage the copper cables that run through the casing from the connector.
After removing the casing you can remove the metal pins along with the springs from the other part of the unit.
With the pins out of the housing you can attach a water hose to the inlet valve on the housing and flush the valve unit. When you are satisfied that it is no longer clogged up you can re-insert the pins not forgetting the springs and put the whole thing back together making sure that you put the hoses back correctly. The valve unit will then need to be clipped back into the rubber that held it in place. This is a bit difficult as the rubber is usually dry (spraying the rubber with wd40 will help).
I would advise you to spray some WD40 inside the unit and a little in the inlets pipe on the valve unit before you put it back together. This will help lubricate the internals and free things up.
Once everything is put back in place top up the water in your radiator as you would have lost some when you disconnected the hoses etc. You may also need to bleed the coolant system although I didn't need to do this.
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