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Volvo 940gl still no heat.

J

Jressman

Member
Joined
Jan 4, 2015
I have a 1992 Volvo 940 that has no heat. A few months ago I replaced the head gasket, water pump, radiator, thermostat, all coolant hoses including hard line. Car runs great, comes up to operating temp very quickly, but has no heat from vents. Here’s what I’ve done so far:

-Changed thermostats twice 88c/192F
-Checked firewall lines for blockage, none
-Flushed heater core, flows freely no clogs
-Bypassed heater valve. Hose from head to heatercore top port. Hardline to bottom port.

Here’s the interesting thing. The heater core hoses are both cool to touch even after the car has been driven for awhile at full operating temp. I’ve gone as far to disconnect them both and run the far while hot and coolant barely flows. If at all. There’s something either blocking coolant flow from the cylinder head to the heater core such as an air pocket, and/or there’s very low system pressure. Not enough to pump coolant into the heater core matrix and out the hard line. I’ve been driving since June without working heat which is a non-issue, but I’ll need working heat for the upcoming Massachusetts winter.
 
Could it possibly be that you need the HEATER Control Valve Inline to get HEAT? Or maybe you got AIR in the System? When refilling the motor with coolant, I fill the BLOCK with Coolant until its just below the thermostat and assemble and then the Reservoir bottle between Min & Max and leave CAPLESS....Upon Starting the car, I like to SLOWLY SQUEEZE tbe TOP Radiator Hose and set TEMP on HIGH HEAT until motor WARMS...Once you got HEAT Comimg from the Vents with motor running, shut down and let settle for 15 min and Add coolant as necessary to top off...Works like a CHARM Everytime but THIS is WHEN a Heater Control Valve is in the LOOP...I ALWAYS keep an Extra or 2 on hand at all times..
 
I had the heater control valve in at first, I tried swapping with another valve I had and still no change. Then I took the valve completely out of the system to rule out any possibility of a valve blockage.
 
Jressman said:
I had the heater control valve in at first, I tried swapping with another valve I had and still no change. Then I took the valve completely out of the system to rule out any possibility of a valve blockage.
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Do you have coolant coming from the hoses going to the heater core? Seems like it based on above
 
doucheNozzle said:
Do you have coolant coming from the hoses going to the heater core? Seems like it based on above
Click to expand...
Very little. I can unplug the hose to the core from the head and hold it upright and coolant won’t come out. I can see it down the hose. When the car is shut off the coolant falls back onto the hose out of sight. It’s like little to no coolant pressure. Not enough to pump it up into the core.
 
Mhh, so you're saying you can unplug any of the 2 hoses that go to the firewall connections while the car is running and no coolant is spraying out?
Sounds to me you're having a general cooling issue, coolant should come spraying out when you disconnect any of the coolant hoses.
Is the water pump working properly? Belt tight? Enough coolant?
 
Mr. V said:
I assume the car isn't overheating?

If it runs okay then I'd suspect there is a blockage somewhere, either at / in the steel coolant pipe or the block itself.
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700/900 gauges don't move until its too late, so it could be running hot and he would never know. My Gauge doesn't move till 250+
 
Jressman said:
Very little. I can unplug the hose to the core from the head and hold it upright and coolant won’t come out. I can see it down the hose. When the car is shut off the coolant falls back onto the hose out of sight. It’s like little to no coolant pressure. Not enough to pump it up into the core.
Click to expand...
Coolant usually builds pressure from getting up to temperature but also from the water pump impeller. Are you sure your water pump is working? I've seen the impeller blades corroded away completely on a jeep, thank god I didn't buy that hunk of shit. Anyways your water pump is the first place I would look, I would also disconnect the hoses and see if you can run a pipe cleaner or something through them, slim chance but you might have some kind of internal one way valve in a hose caused by it deteriorating, kind of like in brake hoses. I would take this chance to just replace all the cooling system hoses and bits

Also, this obviously isn't your issue given the symptoms, but I struggled with getting heat in my car until I figured out that the blend door actuator was broken. Until I got a new used one, I just set it to max heat by popping the guide rod into the further position. Yours is right behind the glove box, you'll know what I mean when you get to that part. My coolant hoses were all hot though.
 
Yeah, his hoses are cold and floe nothing, so it can't have anything to do with blend door, which would have been my first guess otherwise.

What about radiator hoses? They warm up as they should? Radiator as well?
 
Boxtoy940 said:
Could it possibly be that you need the HEATER Control Valve Inline to get HEAT?
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No, because the heater core is always part of the cooling circuit (in COMBU systems with AC, at least). The standard heater valve setup in a COMBU system only cuts off the coolant flow to the heater core (and to the back of the head, danger!) when the recirculate button is engaged. Cabin heat is regulated by the doors and flaps in the heater box.

OP, you say you've changed the water pump, so that should be okay.
Ditto the thermostat (twice).

There is a blockage somewhere - in the head, I suspect.

Why was the head gasket changed? Did it blow, and overheat the engine when it did?

The new head gasket wouldn't be blocking the coolant passages between the block and head, I hope?

And, did you get the head cleaned and checked for warpage before returning it to the car?
 
Pietercc said:
700/900 gauges don't move until its too late, so it could be running hot and he would never know. My Gauge doesn't move till 250+
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Speak for yourself my friend, I have NEVER experienced intermittent or slow responding temps in any my 940t's but I always start off with a refreshening of the whole coolant loop as well...
 
Boxtoy940 said:
Speak for yourself my friend, I have NEVER experienced intermittent or slow responding temps in any my 940t's but I always start off with a refreshening of the whole coolant loop as well...
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Just curious do you have a digital gauge as well? My gauge warms up fast, once it gets to 180 its in the center, then once it hits 250 it starts to move. I know my cooling system is good because Temps sit at 195, when going up the grapevine into LA, a good few miles of full boost it doesn't get over 210.
 
IF your TEMPS are REACHING 250* then I dont believe that your FAN is Working Properly as the 2 SPEEDS are in Conjunction with 2 Different Temps; NONE of which Exceeds 220*.....
 
Boxtoy940 said:
IF your TEMPS are REACHING 250* then I dont believe that your FAN is Working Properly as the 2 SPEEDS are in Conjunction with 2 Different Temps; NONE of which Exceeds 220*.....
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It only hit 250 when I had a bad rad cap, I am just stating that my gauge doesn't move until its way too hot.
 
I would try swapping the TEMP GAUGE in the cluster to remedy the issue....As stated, I have NEVER had an issue like that in the 5-6 Volvo 940's Ive owned...Maybe I got lucky with all the new parts I threw at them..
 
Boxtoy940 said:
I would try swapping the TEMP GAUGE in the cluster to remedy the issue....As stated, I have NEVER had an issue like that in the 5-6 Volvo 940's Ive owned...Maybe I got lucky with all the new parts I threw at them..
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Sorry for OT but I just gotta know, why do you capitalise random words in your sentences?
 
Bet you're one of those who Say "WHY are you Screaming despite I NEVER said a Word..On a side note, I am my OWN Unique Individual and I DONT Aspire to be like NO ONE; You asked, so tbere you got.
 
All good, no offence at all, I was just curious :lol:

@OP:
Do you have access to a infrared thermometer to measure actual temps around the head / thermostat housing?
If there is barely any flow from the water pump, I'd be afraid of overheating and the temp gauge can indeed be a bit slow moving as Pieter mentioned.
 
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