Volvo 940 only blowing cold air

[Laird Scooby]

Originally Posted by Ian21401

I’m trying to find that old thread from 2008 or later but my post history only goes back to 2019.
Is there a way of searching much further back, or is that deleted now?

Absolutely no idea Ian, sorry. Perhaps one of the mods might know?

[Ian21401]

Before starting to drain anything from the system as it is at present. How about disconnecting the heater hoses at the engine ends and see what comes out.
Disconnect the hose from the engine block first. That’s the hose which is connected to the HCV. Does anything drain from that hose?
Then disconnect the hose from the rigid pipe. Does anything drain from that hose and/or does disconnecting it also cause something to drain from the other hose?

[McGandalf]

Hello Volvo gang,

Back to this old chestnut I'm afraid. I've made no progress over the last month or so - partly out of grumpyness, partly out of needing to concentrate on my daily Jaguar X358.

I have found that the inch-diameter hose between (I think) the heater matrix and heater control valve is split. Although fluid should be passing through, it's likely to leak.

I appreciate that original hoses are few and far between, but I presume that a generic hose of 25.4mm exterior diameter (not sure of interior diameter) and circa 20 cm long should suffice.

Question - how do I remove the clutch pedal to give myself access?



There appears to be some sort of pin holding the pedal to the lever that goes into the bulkhead (ringed), but I can't work out how to undo it. I may, of course, be barking up the wrong tree.

(And just how are you meant to embed Flickr images in posts on here - IMG tags don't seem to work…?)

Thanks.

[Laird Scooby]

You'll need 16mm bore heater hose to replace that split one. Needs to be heater hose as it has extra reinforcing in the construction to cope with the pressure and heat.

No idea how to embed images on here, i use postimages.org and then use the "Hotlink for forums" and paste it in my post where i want the image to be.



Look at the fulcrum pin from the clutch to the pushrod - there's a clip on the right hand end - lift the tab on the clip and push it away so the clip slides out of the groove in the pin. Remove the pin to the left, catching the bushes as they come. Further up the clutch pedal there's likely to be a similar arrangement for the actual clutch pedal fulcrum pin.
Not sure exactly on how that's arranged as i have automatics.

The big problem is if that heater hose is split, it will leak. If it isn't, it suggests the heater matrix has been bypassed under the bonnet. That may be why you can't get any heat from the heater!

[Ian21401]

McGandalf,
I’ll post a link to my “how to” as soon as I can but I’ll have to find it first.

[Ian21401]

McGandalf,
As Dave has suggested above, if that short connecting hose is split and nothing is leaking from it then it would appear that there is no coolant in the heater matrix and the heater has been bypassed somewhere. The most usual place is to disconnect both of the heater hoses on the engine side of the bulkhead and join them somehow, usually some domestic 15mm copper water piping. I did that back in 2008 when I had HCV leak problems and was awaiting a new HCV. Simply replacing that short split piece of hose will still not allow coolant to flow through the matrix if the matrix has been bypassed somewhere else. I assume that when you have the engine running the radiator and hoses heat up as the coolant heats up.

The quote, "lever that goes into the bulkhead" unquote, is the clutch cylinder pushrod.
To remove the clutch pedal, first, as Dave has already advised, disconnect the clutch master cylinder push rod from the clutch pedal,(that's the pin that you have circled ) by removing the clip from the cotter pin and removing the pin.
Then remove the clutch pedal fulcrum bolt (12mm and no shims or washers on mine)
Remove the left side support bracket (nearest the transmission tunnel) from where it is secured to the bulkhead . It has one 12mm bolt at the top of the bulkhead and two 13mm nuts on bolts which also secure the clutch master cylinder to the bulkhead. (Leave the loose bolts in place and master cylinder in situ as the cylinder should just hang on the bolts).

This now gives you space to manoeuvre the heater valve out of the bulkhead if you wish to do so.
After disconnecting the hoses and unclipping the two operating cables from the housing I found that the valve and control unit on my car had to be removed as one complete unit by turning it clockwise through 90 degrees to free the lugs from the bulkhead. (It is mounted on the bayonet principle with two lugs (or "dogs") on the moulding diametrically opposed to each other which engage into the "bayonet" fitting hole in the bulkhead.)
Care is required when manouvering the corner extremities of the control housing past the rubber gaiter around the clutch cylinder push-rod, but as the cylinder is no longer secured to the bulkhead this is now possible.
Having turned the entire unit through 90 degress clockwise it should come away from the bulkhead in one piece.
The valve itself is secured to the back of the control housing by plastic clips forming part of the control housing itself so VERY CAREFULLY prise the old valve away from the housing and EQUALLY CAREFULLY locate the new valve into the housing.
The control cables:
The temperature control cable operates a lever on the control housing which pivots at the top right hand corner of the housing. A concave cam on that lever actually moves the valve itself. The same lever also operates the air flap control cable.
When re-assembling I found that it was easier to locate the temperature control cable into the plastic lever before fitting the unit to the bulkhead and fit the air control cable afterwards.
I hope this is helpful.

[McGandalf]

Thanks for all your advice. Detailed, clear and useful.

The short connecting hose is split and was indeed leaking some coolant before I managed to stem the flow using a jubilee clip. It is only a small tear, but will only lead to more pain - particularly as a replacement hose is 4 quid off eBay.

Therefore...I will assume that some coolant is flowing through the heater matrix.

Do heater matrixes (matrices?) expire, burn out, tear or otherwise stop working? As I understand they are mostly conductive brass with a fan within - surely the fan itself is a consumable item? Might I just need a new matrix?

My HCV appears to have unseated itself - I really need to take the clutch pedal off, disconnect the hoses, reseat the HCV and ensure that it will open and close fully when I twiddle the temperature control knob. So thanks for the guidance on removing the clutch pedal. Will try this weekend.

[Laird Scooby]

Originally Posted by McGandalf

Thanks for all your advice. Detailed, clear and useful.

The short connecting hose is split and was indeed leaking some coolant before I managed to stem the flow using a jubilee clip. It is only a small tear, but will only lead to more pain - particularly as a replacement hose is 4 quid off eBay.

Therefore...I will assume that some coolant is flowing through the heater matrix.

Do heater matrixes (matrices?) expire, burn out, tear or otherwise stop working? As I understand they are mostly conductive brass with a fan within - surely the fan itself is a consumable item? Might I just need a new matrix?

My HCV appears to have unseated itself - I really need to take the clutch pedal off, disconnect the hoses, reseat the HCV and ensure that it will open and close fully when I twiddle the temperature control knob. So thanks for the guidance on removing the clutch pedal. Will try this weekend.

The fan is above where the passengers left foot would be, no fan in the heater matrix.

The main thing matrices do when they fail is leak, usually no other faults stop them working.

If your HCV is in the wrong place, it's entirely possible it's just not opening, note that you will get coolant both sides of it, just no flow resulting in no heat if it doesn't open.

[McGandalf]

Fingers crossed a careful reseating and testing of the HCV, then a flush and refill with coolant, will solve the issue then. Lovely toasty air and no more "I'm absolutely freezing, why couldn't we have taken the Jag" from my wife.

(Sod's law it won't!)

[kiloran]

On the plus side, by the time this is fixed it will be summer and you won't need the heater

I wonder if I'm the only one that does this but I regularly run my heater at full blast over the summer months simply because I'm paranoid about things gumming up in the matrix.