Club 80-90 Forums

Did t25’s come with a vw operating booklet when new. If so does it cover the level of the coolant in the expansion tank.

Cecil wrote:I have noticed that there is a max mark on the expansion (darle k )tank.maybe filling it to the brim is not what vw intended and maybe causes debris from the cooling system to collect in the darle k valves or wears them out because coolant passes back and fourth more often . I have noticed with my van that in practice an amount of air space can be left in the expansion tank and not be automatically replaced by coolant by the top up tank. I can’t work out if the top up tank is there to accommodate for lots of expansion/contraction or as a reserve in case of coolant loss.
E D I T- maybe the top up tank’s only function is to provide a way to top up the coolant from the cat flap.

SORRY
I tell a lie just been and had a look , it’s not a”max” mark it’s a “ min” mark .no “ max” mark so looks like full is the intention!

Yep, I've been getting my head around why the WBX has this system at all. Apologies for those who already know, I've only had one for 10 months, 8 months of which it's been laid up. On one of my first outings I was faced with the low coolant warning light, and after stopping twice and then RFTM put water in the expansion tank. This is where I have got to:

Most cars have a single header tank, if there's too much coolant following expansion the excess simply gets expelled through an overflow pipe. It's not a question of system capacity, the Boxster has a similar system capacity but only one tank.

I think there are two reasons, the first is that the header tank is below the level of the top of the radiator so a simple gravity overflow would drain water above the level of the drain on the header tank. The second is partly for providing easy access for topping up without needing access to the engine compartment. Additionally the use of the second one way valve in the header cap allows coolant in the expansion tank to be sucked back into the header tank when it cools, keeping the header tank full.

Quite clever, unless the Dalex exterminates itself

James Akers has some useful downloads here - I couldn't find a WBX owners manual online, but the dealer bulletin is quite informative https://vwt25.blog/files/

You must have missed my previous post. It should be full to the brim from cold. The Bentley repair manual is the official manual for the T3.
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Did t25’s come with a vw operating booklet when new. If so does it cover the level of the coolant in the expansion tank.

I would say that VW were just very cautious with all their early water-cooled vehicles, the T3 system does hold a lot of coolant so there is a corresponding amount of expansion to accommodate.
As for the D4RL3K caps, it might just be poorer quality plastic to blame, if the engine hasn't got a pressurization problem.
Things just ain't what they used to be...

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Cecil wrote:Did t25’s come with a vw operating booklet when new. If so does it cover the level of the coolant in the expansion tank.

You mean this?

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Well i stand corrected.I pulled the knacked cap apart,there is a rubber ring in there. This looks like its in good nick.I think i may of found the answer. There were a couple of small lumps of Kseal in there.I used this whilst away a few years ago.I thought i had flushed it out of the system.Apparently not.
I wont be using it again.

Go on then, reassemble and refit it, it's the only way to know if you have a spare good cap.

I will if i can remember the order of putting it back together

itchyfeet wrote:
or maybe somebody put radweld in and its damaging the cap?

nearly right

good to know that, K seal gets wheeled out regularly as a fix, won't use it myself.

Well, i have just stripped one of the dearer(no trace of Kseal) and one of the cheaper caps. Thoroughly cleaned both, reassembled them. no difference

oh spoke too soon then
I take it these are 'broken ' caps

I can only suggest a new cap and swap the parts one by one and see if you can narrow down which part is failing.

It'll likely be the same component failing all the time.

I learnt many years ago when the only way to get s/h parts was by going to the scrappers and go climbing over the cars to remove them yourself that cars have weaknesses, the same components keep failing, so the bit I needed had probably already been snaffled by someone else.

Yes, non-quackers.I will have to get one next time i order from brickwerks.

Is there an "upgraded" cap available, maybe from another model.

One of my cars has a 1.5 bar cap, so they are made to release at other than 1 bar

...... or given that it's probably just the spring that has gone weak, replace the spring or shim it ?