Heater blowing cold when past setting 2..

[cpjitservices]

Hi all

Recently I have done a coolant and thermostat change, heater blows quite warm when on 1 or 2, any higher and it blows cold.
Have been squeezing the pipe on left-hand side bottom, of rad with header tank cap off to get any air out but have done this quite a lot and still not quite right as soon as it blows warm and switch to number 3 or 4 it blows cool again..... any ideas? ta - Update: the pipe bottom left stays cool, the thermostat side is hot and barely touchable! If I keep squeezing the bottom left pipe it eventually gets warm...

Have also left header tank cap off overnight see if it Gravity bleeds any air out, checked this morning and had well below min coolant, have topped it back up. Number 2 blowing warm, again, number 3 or 4 and blowing cool.

Thanks

[cheshired5]

Do both heater pipes get equally too hot to hold?

[cpjitservices]

Originally Posted by cheshired5

Do both heater pipes get equally too hot to hold?

Not quite, one on the left doesn't get 'as hot'

[cheshired5]

You have a circulation issue caused by either an airlock, a partially blocked matrix or failing water pump.
If it was working fine prior to the coolant change, it's unlikely to be the pump.

Did you flush through the matrix and cooling system both ways with running water?

Some system designs have an additional bleed valve for this kind of situation. Is yours one of those systems?
If so, the valve is slowly loosened with the engine running until air is purged and coolant appears from the valve then you immediately close the valve.

An alternative is to get the engine up to temperature and whilst gently revving the engine, slowly loosen the expansion cap but if the coolant rises enough to escape, tighten the cap again.
Repeat until both heater pipes are equally hot.
Dependant on your system, you may need the heater temperature dial on full before doing the above.

[cpjitservices]

Originally Posted by cheshired5

You have a circulation issue caused by either an airlock, a partially blocked matrix or failing water pump.
If it was working fine prior to the coolant change, it's unlikely to be the pump.

Did you flush through the matrix and cooling system both ways with running water?

Some system designs have an additional bleed valve for this kind of situation. Is yours one of those systems?
If so, the valve is slowly loosened with the engine running until air is purged and coolant appears from the valve then you immediately close the valve.

An alternative is to get the engine up to temperature and whilst gently revving the engine, slowly loosen the expansion cap but if the coolant rises enough to escape, tighten the cap again.
Repeat until both heater pipes are equally hot.
Dependant on your system, you may need the heater temperature dial on full before doing the above.

Yes system was fully flushed, not sure whether I'll have a Valve? Would be an easier way! I have the B230K engine.... if that helps?

Cant see a Valve anywhere!

Yep heater was fine before I did the change, Ill try the filler cap idea you mentioned too. Thanks

[nutco]

This happened to me when the thermostat was put in up side down

Originally Posted by cpjitservices

Hi all

Recently I have done a coolant and thermostat change, heater blows quite warm when on 1 or 2, any higher and it blows cold.
Have been squeezing the pipe on left-hand side bottom, of rad with header tank cap off to get any air out but have done this quite a lot and still not quite right as soon as it blows warm and switch to number 3 or 4 it blows cool again..... any ideas? ta - Update: the pipe bottom left stays cool, the thermostat side is hot and barely touchable! If I keep squeezing the bottom left pipe it eventually gets warm...

Have also left header tank cap off overnight see if it Gravity bleeds any air out, checked this morning and had well below min coolant, have topped it back up. Number 2 blowing warm, again, number 3 or 4 and blowing cool.

Thanks

[cpjitservices]

Originally Posted by nutco

This happened to me when the thermostat was put in up side down

I'll Check but pretty sure its right.

[Laird Scooby]

When you say the heater was "fine before the change", what was the temperature gauge doing before and how hot was the air coming from the heater?

For example, if the 'stat was weak and you were lucky to get the temperature gauge to move off its bottom stop, you won't know if the heater was fine because the engine would never have got hot. If the heater is working correctly and the engine is reaching it's correct temperature then the gauge should sit about half way up and if you put the heater on its hottest setting to the vents and hold your hand in front of them, you shouldn't be able to stand it very long.

If you couldn't have done that beforehand, chances are the fault was already there.

It might pay to swap the two hoses on the heater matrix, easily done under the bonnet, literally undo the Jubllee clips, pull the hose off each stub and refit it on the other stub. Now run the engine up and see if there's an improvement. I've had several cars like this including not only this Volvo, the Jeep before it and the 740 before that. Also had several other cars over the years with the same problem.

If it doesn't improve matters after topping up the coolant both before and after running it up then swap them back as if they are the wrong way round, this will cause a problem bleeding the system.