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Volvo 940 only blowing cold air

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Old Mar 18th, 2021, 13:29   #11
McGandalf
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Originally Posted by Laird Scooby View Post
I'd replace the 'stat before going near the HCV if i were you. Before you start the drain, flush etc, ensure the heater is set to the hottest setting, it needs to be there so the matrix gets flushed too.

When you come to do it, invest in something like Comma X-stream Flush for the cooling system and add it as per the directions on it.

...
Thanks for one of the clearest step-by-step guides to car maintenance I've seen on the Internet. Really first-rate.

Comma X-Stream Flush seems to be no longer available though - Evapo-Rust C715 Thermocure looks like a good alternative.

Have ordered a new thermostat - when it comes I'll run through the steps you suggested. I have a suspicion the coolant in the car might never have been changed in all its 29 years. It is the right colour though (blue/green, if you can still call it that).
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Old Mar 18th, 2021, 13:47   #12
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This gets good reviews for rad flushing https://www.ebay.co.uk/itm/Prestone-....c101197.m1850
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Old Mar 24th, 2021, 20:20   #13
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Originally Posted by Laird Scooby View Post
I'd replace the 'stat before going near the HCV if i were you. Before you start the drain, flush etc, ensure the heater is set to the hottest setting, it needs to be there so the matrix gets flushed too.

When you come to do it, invest in something like Comma X-stream Flush for the cooling system and add it as per the directions on it.

If it says run it at a fast idle for 20 minutes, take it for a half hour drive instead.

Once you're home and it has cooled somewhat, remove the 'stat housing and the old 'stat. Refit the housing then remove the top hose from the radiator stub. Use your garden hose in the open end of the top hose, if you have a Hozelock type fitting it should fit snugly inside the top hose.
Turn the water on for the hose and leave it running. This reverse flushes the system with the old stuff exiting via the radiator stub at the top. Usually takes about half hour to get it running clear, once it is running clear leave it 10 minutes or so more to ensure it really is clear.
Turn the hose off and remove it from the top hose. Remove the bottom hose from the bottom of the rad to drain off excess water from the rad and block and then refit - having a new Jublee clip for it is a wise move as they often rust.
Maybe silly question - after my drive with the coolant flush mixed with deionised water in the cooling system (following an initial coolant drain, do I need to drain the coolant flush/water mixture before flushing through with a garden hose, or should I just go for it?

How poisonous is that coolant flush to wandering cats/others - just bearing in mind that ethylene glycol is notorious for causing irreversable kidney damage to cats (and we have two of the creatures at home)? Or is it the case that the 30-40 minutes of hose flushing will render the poison concentration sufficiently diluted that I'm worrying about nothing?

Finally, how do you get rid of used ethylene glycol coolant - take it to the tip and pour it in the waste engine oil tank?
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Old Mar 24th, 2021, 20:28   #14
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Quote:
Originally Posted by Laird Scooby View Post
I'd replace the 'stat before going near the HCV if i were you. Before you start the drain, flush etc, ensure the heater is set to the hottest setting, it needs to be there so the matrix gets flushed too.

When you come to do it, invest in something like Comma X-stream Flush for the cooling system and add it as per the directions on it.

If it says run it at a fast idle for 20 minutes, take it for a half hour drive instead.

Once you're home and it has cooled somewhat, remove the 'stat housing and the old 'stat. Refit the housing then remove the top hose from the radiator stub. Use your garden hose in the open end of the top hose, if you have a Hozelock type fitting it should fit snugly inside the top hose.
Turn the water on for the hose and leave it running. This reverse flushes the system with the old stuff exiting via the radiator stub at the top. Usually takes about half hour to get it running clear, once it is running clear leave it 10 minutes or so more to ensure it really is clear.

Turn the hose off and remove it from the top hose. Remove the bottom hose from the bottom of the rad to drain off excess water from the rad and block and then refit - having a new Jublee clip for it is a wise move as they often rust.

Once the bottom hose is secure, add 5L of concentrated Ethylene Glycol antifreeze. The exact figure for 50/50 mix is something like 4.8L, can't recall it exactly and it's as close to 5L as makes very little difference.
Fit the new 'stat, note the seal sits around the edge of the 'stat ont on it or under it - there is a groove inside the seal to let it sit around the 'stat. Ensure the recess in the head and 'stat housing are clean and smooth, use some silicone grease in the groove and smear some on the outer parts of the seal too and fit, ensuring the jiggle valve is at the top if it has one.
Refit the 'stat housing and top hose to the rad.

Top up the expansion tank with fresh water (remember you already have enough antifreeze in so water is fine), refit the cap and squeeze the bottom hose several times to help move the air to the top. If the level drops in the tank, add more water to the "MIN" line and squeeze the bottom hose a few more times. Repeat until squeezing the bottom hose doesn't result in further drop of the level.

Refit the cap and take for a drive, ensuring you get it up to temperature and that the heater works, no leaks etc. Return home and park it facing uphill and leave to cool until the following day then check and top up the level to the "MIN" mark if needed.

I've used this method for decades on a variety of cars and it works. Whatever you do, don't be tempted to buy OAT coolant, doesn't matter how good the salesman says it is, it will destroy your engine.

If some idiot has previously used OAT coolant (usually red or orange) then you have other problems and could be the cause of your lack of heat. Hopefully they haven't though!
Quote:
Originally Posted by McGandalf View Post
Maybe silly question - after my drive with the coolant flush mixed with deionised water in the cooling system (following an initial coolant drain, do I need to drain the coolant flush/water mixture before flushing through with a garden hose, or should I just go for it?

How poisonous is that coolant flush to wandering cats/others - just bearing in mind that ethylene glycol is notorious for causing irreversable kidney damage to cats (and we have two of the creatures at home)? Or is it the case that the 30-40 minutes of hose flushing will render the poison concentration sufficiently diluted that I'm worrying about nothing?

Finally, how do you get rid of used ethylene glycol coolant - take it to the tip and pour it in the waste engine oil tank?
I've highlighted the answer to the first part in my post in green above. Just go for it in other words.

The method i've always used is massive dilution, there are many wandering cats around here and none have ever been effected as far as i'm aware. As for the old anitfreeze, yes, catch as much as possible, into an old oil can and down the tip. I usually give the whole area a good hose down after to be on the safe side as well
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Old Mar 25th, 2021, 15:21   #15
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Hi Laird Scooby - I followed your instructions to the letter. Flushed the system initially with Prestone Coolant Flush, followed by a drive, then anything up to an hour of running a hosepipe through the system. I then fitted a new Volvo OEM thermostat as directed and poured around 4 litres of new blue coolant into the coolant expansion bottle to the LHS of the engine. At that point, the coolant expansion bottle was almost full - over the max mark. I pumped the lower radiator hose which produced some air bubbles, but didn't reduce the coolant level in the bottle.

I took the car for a drive and got it up to operating temperature (maybe 10 mins). The temperature needle rose to a midway point - so the new thermostat is working here. However, the air coming out of the vents continues to be cold (cool-ish - certainly not hot) with the heater setting turned to max.

Questions - I appreciate that no amount of draining/flushing will remove all the residual coolant or water lurking in the radiator or engine block, but surely 5-6 litres shouldn't be lurking there?

Also - do I need to give the car a considerably longer run to get hot air to come out of the vents? I have an idea that the concentrated coolant in the the system won't assist warm air coming out - that's the job of the water you top it up with.

The car is currently parked with the front end on ramps - maybe coolant is going to drain backwards from the radiator to the block and reduce the level in the bottle?
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Old Mar 25th, 2021, 16:08   #16
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Are you referring to the side vents as the air coming out of the two middle vents is always cool.

If you drain with the heater vent turned to fully warm you should get more than 4 litres out
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Old Mar 25th, 2021, 16:28   #17
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Yes - I've checked all vents, middle and side. All are blowing cool air.

I drained the engine with the heater valve set to warm (as far as it would go).
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Old Mar 25th, 2021, 16:50   #18
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Thats odd ? I take it you drained from lower rad hose ? Did you measure how much came out on the first drain ?
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Old Mar 25th, 2021, 17:07   #19
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Thats odd ? I take it you drained from lower rad hose ? Did you measure how much came out on the first drain ?
My first drain was from the lower rad hose, the top rad hose, and the hose between the coolant expansion bottle and the radiator. I also loosened the coolant screw hidden behind the LHS of the engine block, and drained as much coolant as I could from here.

Altogether I managed to fill 8 litres in a bucket - although some ended up on the ground as i'm cack-handed. Assuming 9-10 litres came out of the system in total.

I later flushed hosepipe water through the system for an hour. It could well be the case that there is still some of this water in the engine block, although I did drain it from the lower rad hose. I didn't bother to undo the hidden coolant screw after the hosepipe flush as it's a pain to access.

I'll give the old girl a good blast this evening and see if she produces any warmer air.
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Old Mar 25th, 2021, 17:10   #20
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Quote:
Originally Posted by McGandalf View Post
Hi Laird Scooby - I followed your instructions to the letter. Flushed the system initially with Prestone Coolant Flush, followed by a drive, then anything up to an hour of running a hosepipe through the system. I then fitted a new Volvo OEM thermostat as directed and poured around 4 litres of new blue coolant into the coolant expansion bottle to the LHS of the engine. At that point, the coolant expansion bottle was almost full - over the max mark. I pumped the lower radiator hose which produced some air bubbles, but didn't reduce the coolant level in the bottle.

I took the car for a drive and got it up to operating temperature (maybe 10 mins). The temperature needle rose to a midway point - so the new thermostat is working here. However, the air coming out of the vents continues to be cold (cool-ish - certainly not hot) with the heater setting turned to max.

Questions - I appreciate that no amount of draining/flushing will remove all the residual coolant or water lurking in the radiator or engine block, but surely 5-6 litres shouldn't be lurking there?

Also - do I need to give the car a considerably longer run to get hot air to come out of the vents? I have an idea that the concentrated coolant in the the system won't assist warm air coming out - that's the job of the water you top it up with.

The car is currently parked with the front end on ramps - maybe coolant is going to drain backwards from the radiator to the block and reduce the level in the bottle?
I'm pretty sure you missed "Remove the bottom hose from the bottom of the rad to drain off excess water from the rad and block and then refit - having a new Jublee clip for it is a wise move as they often rust." from just past the green section above.

*** EDIT *** this is after the flushing!!!

That would have made room for more than 4L of coolant!

You may have a massive air lock but i doubt it if you followed my directions. Can you find the two heater hoses feeding the heater matrix on the bulkhead and trace each one back to where they join the head and/or inlet manifold and the metal pipe that leads round the back end of the bloock, under the exhaust manifold and into the water pump? I suspect they may have been swapped at some point if you're still not getting heat out of the heater or the temperatue control isn't moving the flap and/or the heater valve on the inside.

To check whether the heater valve is opening, push the heater temperature control to hot and then look at the heater valve. If memory serves where the cable attaches to the valve, the arm it attaches to should be in line with the two stubs for in and out.
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Last edited by Laird Scooby; Mar 25th, 2021 at 17:14. Reason: Calrification
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