coolant drain and flush

[crazygrazy]

hello all i have a 2002 tdi 115 was wondering if there are any threads on draining coolant, flushing and refilling .Just got some g30 ready for the winter i have the pressure building prob commonly posted about but never overheats done 7000 miles in her no probs , dodgy hose perhaps ? . I have been unable to find any guides on here and as always any advice would be greatly appreciated many thanks

[insanitybeard]

Greetings!

I don't think there is a procedure in the reference library as yet regarding coolant draining, flushing and refilling.

To my knowledge there isn't a drain plug on the radiator, at least there definitely isn't on the 130ps TDI rad, the rad on the 115ps is slightly different though...... Anyway, regarding the procedure it really depends how thorough you want to be, if you want to go the full nine yards then...........

Remove the header tank cap, take the lower radiator hose off (best with the engine cold!) and dump the old coolant into a container of a least 8-10 litres capacity (have a few empty sealable 5ltr containers handy you can dump the old stuff into and take to your local recycling centre for disposal), you won't get all the coolant out this way as there will be coolant stuck in the rear heater pipework as well as the cylinder jacket which won't drain with the thermostat shut. Once you've drained as much as will come out just by pulling off the bottom hose, then you can remove the upper radiator hose and feed a hosepipe into the upper port of the rad, then flush the radiator through (try to catch the initial fluid that comes out of the lower port on the rad as you don't really want coolant going down the drain!) until the fluid coming out is clear and free of any debris.

With the rad cleared out then you can turn your attention to the rest of the system. If you want to get as much of the old coolant out as possible then you can get underneath the vehicle in the area of the nearside rear door and disconnect one of the smaller bore coolant pipes that emerges from the booster heater (the lowest point of the system) and let as much coolant as possible drain out (into your container of course!). Once you've caught as much as possible, reconnect the hose and then you can feed water into the (still removed) upper radiator hose and let it flush through the system (obviously it'll emerge from the still disconnected bottom radiator hose), once the fluid runs clear and debris free then stop flushing and let as much of the plain water you've introduced to the system drain out (removing the rear booster heater hose again if needs be). With the system as clean and drained as possible, refit all pipework and then you can begin refilling. Usually coolant needs to be mixed/diluted 50/50 with water (if you're extra fussy like me you can use deionised water to dilute the antifreeze with instead of just plain tapwater), as there inevitably will still be plain water in the system from flushing it I wouldn't bother diluting the first litre or so of antifreeze you put in. Beyond this, dilute the antifreeze as required and refill via the header tank until it's up to the max mark.

I'm sure there will be some debate on bleeding the system through and how best to accomplish this, but on the PD engine used in the Mk2 Galaxy (which has no bleed valve in any of the pipework that I'm aware of), the fact is if you leave it running at idle it'll never get hot enough to open the thermostat and bleed the air from the cylinder jacket. Even if you rev it without any load on the engine I don't know how long it would take the engine to get hot enough to open the thermostat- from cold, my Galaxy takes a few miles of driving even with load on the engine to lift the temp gauge off of the minimum!

So my method, which may not meet universal approval was to leave the engine running at idle for 10-15 minutes to warm up a bit and bleed as much air as possible with the thermostat still shut, then ensure the level was still up to the max mark on the header tank, refit the cap and then go for a gentle drive armed with 2-3 litres of ready mixed fresh coolant. Have the heaters cranked up as well to help purge any air from the heater matrixes. After a mile or so, or when you see the temp gauge start to lift, stop and open the bonnet, carefully release the header tank cap, (ensuring any pressure is released before fully removing the cap- you don't want to get scalded!) check the level, top up if required, refit the cap, drive on gently another mile or so and repeat, until you see the level in the header tank drop drastically. What tends to happen is that when the air purges, it tends to do it in one go all of a sudden (when the thermostat opens), so go easy and check regularly! You don't want to be driving for long with an empty header tank!

Once you're happy the air is purged and you've topped the level up to the max then you can drive more 'normally', once the bulk of the air is purged usually there's a little bit more air still left in there which will work it's way out as you drive, and usually you'll find if you drive the vehicle then leave it overnight then any remaining air will be purged as the engine cools, so the level will have dropped a bit when you check it from cold in the morning. Keep an eye on the level for a couple of days just to make sure it doesn't drop any further and double check for leaks.

Hope this helps! 

[crazygrazy]

Thankyou very much will atempt this when rain subsides  done filters and oil today damn pollen filters a mission , lucky had a post to help me. Must say this forum is better than a manual once again thankyou for your help saved me a fortune

[Mirez]

If you could take some photos when you do it then we can tally them up with Paul's post above and make another how-to!

[George106]

To heat engine up I always use aux heater (of course ambient sensor bridged or modified to s switch).

[crazygrazy]

Ok mirez will do still hammering it down here , thanks for help and advice once again much appreciated. 

[Chrispb]

I've always found  they bleed out easier when car's facing uphill, providing the restriction is clear in the small return hose air trapped in the engine waterways and heaters will bleed back to the bottle when engine is running, a small amount of air may get  trapped on the radiator side of the thermostat this will release into the engine when the stat starts to open as it approaches normal operating temperature, I tend to leave the cap off until the stat has opened then top up to bring level back to the maximum mark.

[crazygrazy]

Thanks for advice all attempted today couldnt take photos sorry dropped phone in catch bowl im a donut , but worryingly only got about 5 litres outta her and only just managed to get 5 back in followed procedure explained took an hour to get it all in too?  Takes an age to warm her up anyway will keep checking and topping up any ideas why this could be ,thanks again for everyone's  advice amazing forum

[insanitybeard]

No worries! Sorry about the phone......... 5 litres is a reasonable amount of coolant to get out if you've just pulled the radiator hoses off, you'll only get appreciably more out if you remove the water pump or thermostat and drain what's in the cylinder jacket as well really.

Yes, the TDI does take an age to warm up from cold, unless it's being assisted by the booster heater. Diesels are worse than petrols in this respect, and especially the PD engine due to high thermal efficiency, plus it's got a fairly large cooling circuit. In the colder weather with gentle around town driving, I can drive for 20 minutes plus and still the temp gauge won't have reached mid way (90 degrees), leave it idling for the same amount of time and the gauge won't have even moved off of minimum!

[crazygrazy]

Cheers fella , is it possible for thermostat to get blocked just wondering because water that came that way was quite sludgy , can I flush block for example , will check to see water pump is working properly next said cam was changed 20 k ago but no mention of water pump in stamp book? Thanks again awesome guys

[Chrispb]

Pressurising and now you mention sludgy coolant indicates to me your car has suffered overheating/boiling over at some point possibly before you acquired car, do you do any hard motorway driving as this will be when overheating occurs, driving around town usually causes no problems but feel it may only be a matter of time before head gasket failure rears it's ugly head.
You should also check out your auxiliary coolant pump (behind fuel filter) and booster heater (under car) passenger side as well as the engine water pump and stat.
There's more info on these items in our reference library.

[crazygrazy]

Yes have done about 7k in 4 months about 300miles each way at  a time uses water but has never over heated shes  been a good girl sat in traffic jam for four hours still no probs. Will check pumps etc was worried it may have common issues but looking to replace next year any how just trying to prolong her life till then, was an ex taxi lol and done 184k  .will investigate further strange girl on good day and dont wanna throw mega money at it cost me arm and leg since got her suspension , brakes, mcpherson struts why decided to start doing bits myself . Think aux pumps had it will look into booster heater didnt know had one dont think that works either maybe hit the panic button time thanks again chris advice much appreciated.