Topping up water/coolant
 

So what’s the best way to go about it? I’ve noticed my overflow bottle is on the low mark even after driving. Do I fill from header tank very slowly on cold? Do I switch the car on and fill? Do I fill the radiator? Do I fill overflow as well?

From stone cold, remove the header tank cap by the turbo. Level should be up to the bottom of the neck.
Top up if need be and put cap back on. This cap has the two ears on it.

Then take off radiator cap, again should be full, top up if needed and put cap back on. This cap is just round, no ears. Don't take off these caps at the same time as you'll lose coolant from radiator neck (gravity feeding coolant from header tank). Also don't mix these caps up - ears on header tank, round on rad.

The overflow bottle (near the battery) is ok to be low on cold as when the engine gets hot, coolant expands into that bottle so the level rises in there when hot. Overnight it gets sucked back in to the coolant system, taking you back to the cold level in that bottle.

There are two plastic lines on that bottle saying LOW and FULL. On cold top it up half way between the two lines
Regardless of the level on cold in the overflow bottle, it will rise an inch or two when hot. If you're on LOW after a drive, you may need to top up the system.

Work from stone cold and from left to right 1 - 2 - 3
1 Header tank
2 Radiator
3 Overflow bottle

Very well explained. Thanks sir!

Cheers for that, i wasn't never sure myself where to top up from if needed, just assumed you would top up via the overflow tank:thumb:

I've certainly found it the best way as above. Stone cold primarily for safety of course....but also for the most accurate levels you can possibly get.
I have a 2.5 so no surprise I know a thing or two about checking my coolant levels to death! lol

Same here have a 2.5 also, but up to now in my 8yrs of ownership ive had no real issues touch wood.

You're lucky! I had a forged build done at 45k miles, then the block went at 85k miles. So now on second build. Had it 9 years now which is insane, I have a Passat for a daily lol

Bummer then hey, mine don't get used enough to be fair, got it in 2014 with 58k on it, here we are in 2022 and it's now reading 65k, so done 7k in that time lol ive gotta MK4 golf GTi as a daily plus can use he other halfs Seat Leon if i fancy a change, not cheap tho running 3 motors:freak3:

Never underestimate the longevity of the Golf Mk4....arguably the best Volkswagen ever made. My mum has a Mk 4 year 2000 1.9 TDi, 42k on the clock, we drove it out of a VW showroom in Hamburg. Underneath is mint - literally one careful lady owner. Drives like new! Back in the day you could import a full UK spec car bound for UK showrooms and save around £4,000 even after the travel / hotels etc. It was some sort of import loophole, a full UK car at European prices - now we just all get ripped off.
My dad got a new Passat Estate from Holland the year before in the same way.

Here's my bad day, with a few pics. My overflow bottle would fill, but the header tank was always full - HG is usually overflow full, and header tank half empty. It never overheated once.
A new block cost me about £1250 + VAT.....before any forged build bits and labour etc....man it was a bitterly painful one. My Manley rods were re-used, but that was about it, everything else....paperweight.

https://www.scoobynet.com/scoobynet-...ot-pretty.html

Yeah the MK4 is the best shape in my eyes but im being biased haps lol had it 12 yes so a good reliable run about, your mum gotta bargain then coz i paid 5k for mine back in 2010 when it was already nearly 7 yr old, mine being an 03 plate, but it's now 19 yr old and still going strong:thumb:after reading thru that link to your thread first thing i'll be doing later is checking all my water levels:Suspiciou

Yep, with a 2.5 it's critical to monitor coolant behaviour, it can signal things going on.
Was strange on mine when the block went. HG's is normally overflow tank filling, and header tank half empty. But this time the overflow tank was filling and header tank (and rad) were full. Tried bleeding off the air with a Lisle non spill funnel kit....nothing worked. Only the open heart surgery could reveal what had happened.

Unlucky, or perhaps the coolant even froze and cracked it. You can get a cheapo coolant tester from Halfords for about £9 which indicates the level of protection before your coolant would freeze. A turkey baster with coloured discs in it basically, you can take a sample easily from the overflow tank by the radiator. I suspect though it was cylinder flex that saw my block out.

You want around 3 discs to rise to give good protection from freezing in our UK winter temperatures.

I've gotta tester in the garage and will check it over, to be fair never had any issues thus far with water usage/loss but can't be to careful hey, and the anti freeze strength was checked/topped up when it had a full service and cambelt/water pump change last August, old cambelt had only done like 6k but had been on the car nearly 6yr so was due a change coz of age rather then mileage.