after 27 years I can't take the leaking heater matrix any longer..I have isolated it and plugged the water hoses into the air con evaporator..problem is that the system will not push the coolant through it...has anyone else tried this? it should take the pressure and gravity feeding with coolant works, but even after removing air locks I can't get any movement through the matrix..

on the high pressure entry side, there is a brass type fitting, but it is so tight I wonder if I will tear the aluminium of the matrix my removing it..I wonder if that is the prob as it is acting as a restriction to the fluid? I have fitted a valve so I can shut it off in summer...anyone tried this?

 

Depending on the year and model of your car the AC may have an orifice valve inside the high pressure fitting. Also I would suspect you need to remove the receiver/dryer can so you only have the high and low pressure lines at the firewall. Now after doing this I believe the AC evap. will no longer be good . Would be easier to just replace the heater evap.

 

are you talking about a leaky heater valve, so the heat is always on, or are you talking about a leaking heater core, so hot engine coolant is leaking out in the center console ?

and, is this car a 240 or a 740/940 ? 7/9's have the heater valve behind the engine, while 240s have it near the drivers foot.

 

its 940..the heater matrix has rotted and I know its a nightmare to get at, having removed one from a 740...I just don't have the time. The orifice valve...hmm...that may be what is attached to the high pressure entry side...that is what I couldn't remove. I have removed the dryer...the compressor failed a couple of years ago and the whole system needed replacing so I thought I would just make the most out of what is left. I will try to get the orifice valve off. I think the issue is that the water pump just will not push the coolant through the evaporator. I know its not designed to, but even if I can get some heat out of this arrangement the wife will stop complaining as she drives the car as she refuses to drive the s40 as it has a manual (and admittedly nasty) gearbox).

 

oh. now I see what you're trying to do. huh. yeah, I doubt the orifice in the AC evaporator will allow more than a tiny amount of water, not nearly enough to heat.

940 heater cores are a lot easier than 240 ones, fwiw.

if you're going to go without a heater, just loop the heater hoses together at the back of the engine its a shame... I found the 940s had very quiet and effective heater/ac.

 

will tinker around with it, as I have to keep the car drivable for obvious reasons. I think at every car factory, there is a ghostly line of heater cores just waiting for an entire car to be built around them just to make sure they will never be seen again except by the most persistent and hardy of home mechanics. Removing the valve on the high pressure input of the evaporator might reduce the restriction...its brass onto aluminium, so if I am too keen I will tear the aluminium...its the new Pepsi challenge...

 

7/9 heater cores might be easier than 2's but the job still sucks. Did a heater core on my '92 940... interior was never the same.

Blower motor though is a 20 minute job on a 7/9... unlike a 2.

Anyway... if you want heat on the cheap and easy this MAY BE a solution....

 

yes..I have seen those...will check that out...with anything plugged into the ciggie lighter you have a 20A max and a serious risk of melting things if you exceed it...

I managed to cut that valve off the top of the evaporator and it was a spring no-return type so no wonder the water pump could not manage to get the coolant through. After letting the system settle the air locks seem to have come out and I now have triumphant levels of heat pouring out of the vents without the glycol mist...sadly the wife is not happy as she can still smell the glycol which is probably coating the inside of the cooling system...I guess it will go eventually...but now we have heat which is the main thing. The valve works if I shut it off manually. Will eventually rig something to switch it off from inside the car..the valve is from a 92 Camry...
Thanks for everyone's suggestions even though what I was doing was not really within the true spirit of Volvo (it will take 12 hours and rip the skin off my hands) maintenance.

Next I will tell you all about my cunning rubber engine mount fix (superglue) after all, that stuff only really sticks skin and rubber...

 

yes, Scotty is 100% correct about the ciggie lighter heaters..total rubbish. The one he tried out looks like a goer...fused as well, very sensible. It saves messing with inverters etc which can mean your alternator can't keep up with the vast demand..

 

an electric heater is going to need at least 500 watts to generate anywhere near sufficient heat. most standalone home electric heaters are around 750/1500 watts (low/high). at 12V, 500 watts is about 40 amps, thats a LOT of current to be pulling off your alternator. and 40 amps, you'd better use 8 or 10 gauge wiring, AND have a hefty relay to disable it when the engine is off, or you'll flatten the battery in an hour or two.

 

yes..it is amazing how much power you need to draw to get any heat...there is no substitute to tapping heat off the engine...