Expansion Tank

[randbk]

My ET is leaking. Can I just replace it and then top up with the necessary mix of water and coolant or do I have to bleed the whole system? If so, can someone please explain why the system ever needs bleeding at all?
Thanks

[Ian Hulley]

Coolant needs to be under pressure to increase it's boiling point, air in the system creates airlocks and prevents the coolant doing it's job.

Instructions for bleeding are on the wiki

Ian

[AdrianC]

My ET is leaking. Can I just replace it and then top up with the necessary mix of water and coolant or do I have to bleed the whole system?

By expansion tank, do you mean the "always-full" one with the Dalek, or do you mean the one inside the catflap?

The catflap one's the real expansion, and - no - that certainly doesn't need bleeding.
The Dalek one shouldn't need bleeding, but it may get a bit messy everywhere. If you're quick, though, you should be able to get it swapped with minimal loss.

(I'm assuming WBX - if it's a diesel, it might be different)

If so, can someone please explain why the system ever needs bleeding at all?

Bleeding gets rid of air. When you fill the cooling system from drained, there are various high points where air can gather, and not easily get out of. You need to release that air with the cooling system warmed up and engine running to get the pressure that Ian mentions.

It should never need bleeding (or topping up) between coolant changes - EXCEPT if there's a leak. And, on our vans, there inevitably is.

[Cruz]

My ET is leaking. Can I just replace it and then top up with the necessary mix of water and coolant or do I have to bleed the whole system? If so, can someone please explain why the system ever needs bleeding at all?
Thanks

What year is your van?

There were 3 types of header tank on a T25. An early early version from 82/83 when the first watercooled engines were introduced, a slightly changed early tank from 83-85 and then the final design change from 85 onwards. All 3 are different and the two first early version have two additional pipes that need swapping too.

[randbk]

It is a 1990 year 1900cc petrol, water-cooled,vehicle with a DG engine

[Cruz]

buy a late tank from brickwerks. replace. refill. rebleed.

If the header tank bottle is the problem

[pionte]

I dont think that you will need to bleed ,at least not a full bleed as in removing the radiator bleed screw. compress the rubber pipes with molegrips or similar before removing ( dont go too tight, and protect the rubber with a rag ) that way you wont loose any coolant from the pipes, take of one pipe at a time, catch coolant in a bucket.Fit new tank and refill. Might as well replace the blue dialek cap , BW do one for under a tenner.

squeeze the rubber hoses repeatedly quickly , this will help get any air back out, run up the engine with cap off, keep squeezing hoses, feel as they get hot... fill to the top, refit cap and all should be ok.

fill the tank behind the number plate to the required level. drive around for a bit and keep an eye on the levels.

Martin

[Ian Hulley]

It is a 1990 year 1900cc petrol, water-cooled,vehicle with a DG engine

Add that info to your signature

[tonytech]

And Ill Stress dont buy a crap JK one.
Brickwerks or VW.
T

[lloydy]

I was a bit clever the other day..... Drained and fitted a new water pump (diesel) refilled and it had a leak from the o ring seal did not want to do all the bleeding again. So I got a small diameter hose pipe and fed it through the expansion tank, down the hose to the water pump. Bucket on the floor and syphoned it out, removed pump and sorted o ring, refitted pump. Lifted bucket up above engine and the coolant syphoned back in and filled up from water pump level (hose still down there). Remarkably all the coolant from the bucket went back in, added about a mug full of water to top off the tank. No air locks, no bubbles no bleeding

[Cruz]

And Ill Stress dont buy a crap JK one.
Brickwerks or VW.
T

I assumed they were all made by Meyle? Brickwerks are Meyle and the one I recently got (in an emergency) from Heritage was Meyle and even came with a OEM Blau dalek cap on (Blau make VW caps)

[tonytech]

I dont know who makes the JK ones, but the one I bought from them leaked from the middle seam.
It was lighter in weight and more translucent than the VW one I replaced it with.
T

[Cruz]

The Meyle one's are white and I have nothing to compare it to other than my early early bottle which was a mank yellow.

Maybe you got a bad-un?

[Simon Baxter]

There were some iffy ones a few years back, really thin, not seen any for a while though, I think they were Topran?
Febi and Meyle are nice and thick, but even they change over time. Febi and Meyle are reboxers of other peoples parts so if another supplier comes along with a better deal they do the same as everyone else would...

[Plasticman]

I was a bit clever the other day..... Drained and fitted a new water pump (diesel) refilled and it had a leak from the o ring seal did not want to do all the bleeding again. So I got a small diameter hose pipe and fed it through the expansion tank, down the hose to the water pump. Bucket on the floor and syphoned it out, removed pump and sorted o ring, refitted pump. Lifted bucket up above engine and the coolant syphoned back in and filled up from water pump level (hose still down there). Remarkably all the coolant from the bucket went back in, added about a mug full of water to top off the tank. No air locks, no bubbles no bleeding

typical plumb wallah method