How do I change the two heater hoses? Do I need to remove anything else first, or is it fairly straightforward? And particular tips?
I wouldn't bother replacing heater hoses unless there were signs of deterioration (cracks/softening), or it was a rebuild of some kind, or, you'd already bought them and figured why not because I already have them, LOL.
Additionally - and I admit I'm not sure on this (someone please correct I'm wrong), but in 30 years of driving (one car for 7 years, another for 10 I think, maybe more), I've never replaced heater hoses. I've never HEARD of anyone in my family replacing them in their cars either. (Doesn't mean they didn't though.) Out of the 5 cars I've owned (for any good length of time) I think I've changed only two pairs of radiator hoses. One in a non-volvo because they had gone soft and gel-like, were suctioning-in on themselves - and because I was fitting a re-cored radiator at the same time. The one 240 I did it on was because I had no idea of knowing when or if the they had ever been done - plus I was replacing a weeping water pump at the time.
This is the main bit I meant for others to correct if need be:
Whilst heater hoses are more robust, radiator hoses have much thinner walls. I've never had one split. But I have seen them burst on other people's cars. So I'll make what I think is a reasonably safe guess - that they're designed to be the weak point. i.e. Radiator hoses have a much wider diameter - to provide a good water flow to cool the engine when the thermostat opens - but they also have thinner and softer walls - so they would fail/split long before the heater core hoses would.
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Should I flush and then replace all hoses, or put the new hoses in and then flush?
If you're replacing the heater hoses I would flush first. Then pull the hoses off and wipe around with an old towel. Because sometimes it's a struggle to get new hoses back on with lots of water around. I have weak hands too which doesn't help in my case. Pretty sure I've seen the mechanic use some type of red grease when he's having trouble getting hoses on. (Possibly o-ring grease.)
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I've never changed a thermostat before. Is it located at the top or bottom radiator hose on the B230?
Top hose - where it meets the engine - inside that metal housing secured with two nuts:
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And should I use some of that gasket sealant stuff with the new gasket?
Can't hurt. Better than having to remove it again because it's leaking and find you destroy the new gasket and need to find another one. Be careful not to gouge the metal surfaces when removing the old gasket too.
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I shouldn't have to ask this, but - as the radiator doesn't have a cap, presumably I just fill the system from the overflow tank, with the engine running?
Basically, yes. However:
1. First I would test the new thermostat. Ok, they may have an extremely low failure rate, and may get tested at the factory - but - I hate doing the same job twice. So I'd rather SEE it open myself before sealing it in. Put it in a saucepan of water on the stove (without the rubber ring fitted, so that can't touch the bottom of the saucepan and melt). You can use a thermometer if you have one. But don't be too bothered, nor surprised, if it doesn't open until several degrees higher than the temp on the packet states. What matters is - that it does open - and close again after you remove it from the stove and the water cools down. (You can add a little cool water in - slowly - to speed that second bit up.)
2. If car has been running, wait until it's cold.
3. Flush the radiator with water. Even if it's new. Just in case there's something living in there that shouldn't be. If it's out of the car, great - tilt it in such a way to get nearly all that water back out. Then sit it in place.
4. Your car should hold approximately 9.2L of coolant. However, you can only remove about 5-6L of that by draining. So in the past I have blown into the system to get a bit more water out. I've read some guys switch the hose on their vacuum cleaner to the reverse flow output, shove that in to force water right through the system (with the heater core open) before refilling.
(Apparently if the mix balance is way out, it can erode the engine coolant passages. And if you're adding premix to a lot of water still in the system from flushing - who knows - can that throw the coolant balance right out?)
<B>But maybe the coolant nowadays allows for that - anyone?</B>
In the past I have seen a mechanic test coolant - using litmus paper or something similar(?), and adding more water or coolant concentrate to get the correct balance. You can also buy hydrometers that measure the specific gravity of the coolant. (I know medical test strips have a pretty short accuracy life. So I suspect ones for cars would too. So maybe it makes more sense to buy a hydrometer?)
If you buy concentrate use de-mineralized/de-ionised water. If you can't find that then distilled water. Don't use tap water unless you have no other choice. Most people will just buy premix. But maybe the concentrate and water is a lot cheaper - I don't know.
Oh - and later on - don't mix coolant types. Make a note of what you buy and buy the same thing if you need to top up - it can change the composition of the coolant. (Unless you're completely flushing again - put all new and different stuff in.) Most people use green. I use red. I figure if it costs more and has a longer life span, then why not.
Most people couldn't care less to go the extreme of blowing water through. They don't keep cars long enough so who cares. But I think I overheard the mechanic telling one customer their particular car was notorious for head erosion if the balance wasn't right. But tbh, I'm really not sure - it's only scraps of a memory from years ago that maybe doesn't relate to these cars.
Anyway, if you were going to go to that level, since you're replacing everything anyway - you could remove the thermostat, screw it's housing back on to make a reasonable seal, shove the vacuum hose in there and seal it with your hands, and pull the bottom radiator hose off at the engine (if you already fitted the new one). Again with the heater core open - to heat. I think that covers the water flow path anyway - it's difficult to picture it without an engine bay in front of me.
5. Put all the hoses, thermostat, etc. on.
6. Some cars can get an airlock when you refill, causing the engine to overheat. But I think there has to be something seriously wrong with our cars for that to happen - like a blocked radiator - because I think the thermostats on our cars have a small hole in their disc. Now I can't recall without going to the garage and pulling the bonnet. But IF the bottom flat edge of the thermostat housing (above picture) is NOT level... then you can rotate the thermostat in the housing first, before sealing it in... so that tiny hole in the disc is at the highest point. (Air rises in water and so any air lock will be released by bleeding through that hole.) Obviously if the bottom of the housing IS level, it won't make any difference.
I've also read you can loosen the nuts on the thermostat housing until coolant weeps out, to clear an airlock. But this means cracking the seal you just made - so save it as a last resort.
7. Start fill the system via the overflow tank up to one of the lines (doesn't matter much which one yet). Leave the cap off. Now start the engine. Remember to leave the cabin heater slider set to heat so it fills with coolant too. Wait and watch the water level at the overflow tank. You may need to add some immediately. But after a few minutes the thermostat will eventually open. The coolant will drop suddenly, travel into the engine, and some air will travel out. Add more coolant to the same line as before. Run it another... I don't know - 10-15 minutes maybe? Now top up to the TOP line (if it dropped again). Screw the cap on. Leave the engine on another few minutes and look everywhere for leaks. Check the level and for leaks again after a several-km drive just to be 100%.
Note: If the thermostat disc doesn't have a small hole in it, and/or the engine overheats anyway regardless, I *think* there's a fitting on the block somewhere to bleed the system. You'll have to ask others in that case, because I've never paid attention to it's location, as I've never had to do that. (I said I've rarely replaced radiator hoses, but that doesn't mean I haven't replaced coolant several times.)