Coolant leaking from expansion tank

[Shotage]

Hi all.

Only had my van a week and have run in to a couple of issues.

Today's issue, spotted a relatively small amount of coolant leaking from the expansion tank after a 45 minute journey. I only noticed this as it was dripping on to the exhaust and I spotted a small amount of steam.

I did look at the expansion tank that the coolant was leaking from and couldn't make up my mind if it was low or not. I wanted to look inside but I think that requires removing a tube first? so opted not to.

We let the van cool down and then topped up the top up bottle and drove home. No more signs of leaking coolant and the van drove fine.

I realise now that I should have checked the expansion tank as it's the important one!! I will do this tomorrow.

So if it is low, then I think I need to bleed the system, right?
https://club8090.co.uk/wiki/Co ... ing_system" onclick="window.open(this.href);return false;

But why did it happen? I read somewhere about head gasket possibly causing the expansion tank to over pressure and spill? or is this something that can just happen?

Just in case it's relevant, we recently cleaned out the carb as the van was losing power and to the point of backfiring. Since this work the van has been running pretty much fine.

Any words of wisdom would be much appreciated. I really don't want to wreck the van I've only had a week. I'm not going to use it until I know how to proceed.

Thank you in advance.

Andy

[CJH]

From what you've written it sounds like the leak you've noticed is from the header tank (to use the naming convention used in Simon Baxter's bleeding guide). If it's dirty then it can be difficult to see the level. This tank should be brim full. As the coolant expands it overflows via the dalek cap into the expansion tank, and as it cools, provided your system is gas tight, it draws water back from the expansion tank. I say all this just to clear up which tank is which.

It's not uncommon for the header tank to leak and drip onto the exhaust. It's one of those amusing ironies that the sender in the top of the tank, that's supposed to tell you when the coolant level is low, can leak - there's an O-ring which goes flat with age. When the system pressurises the water is forced out, and when the system cools, instead of sucking coolant back from the expansion tank it just sucks in air around the level sender seal. A leak anywhere else will also cause air to be sucked in in preference to pulling coolant back from the expansion tank.

You should also check the water pipes into header tank, and the dalek cap itself. The trouble with cooling system leaks is that they tend only to happen when the system is hot and pressurised, the coolant then comes out as a fine spray somewhere, and by the time you get the engine cover off to look it will have evaporated and there'll be little sign of the leak. Look for a fine haze of coolant colouring (pink or green or blue, depending on what's in there) around a pipe union. But if you've noticed a leak from the header tank that is obviously the first thing to fix.

If the level's got too low in the header tank, then yes, you should be bleeding the system. You may be lucky and find that just topping up to the brim when cold will be enough. But you need to fix that leak.

[Shotage]

Thanks so much.

Okay, I'm pretty sure that it escaped through the sender switch as I could see a small puddle of coolant around it.

So this sounds like a new O ring and bleed the system, by the sounds of it, do you think?

Many thanks again.

[CJH]

Yes, coolant in the depression around the sender certainly narrows down the source. The only other way for it to gather there is if the dalek cap doesn't seal. The O-ring is cheap (e.g. Brickwerks), but I renewed the whole sender.

If this is your only leak (and that's a very big IF), then the coolant loss won't have been too great - once the system is fully pressurised and all the excess coolant has been squeezed out past the sender, it can't lose any more. None will be drawn back from the expansion tank when it cools. So in this case you will probably get away with removing the dalek cap and topping it up while cold. However, if the resulting level was too low, air will have been drawn around the system, and you'll have to bleed it.

[T3luestar]

I had the same small pool of coolant around the sender switch, turned out to fine hairline cracks in the expansion tank and not the seal.

[Shotage]

Thanks.

Didn't seem to be any signs around the dalek cap or tube, I would say the leak was definitely below that point.

I will also look out for fine cracks in the tank around the switch too, thank you.

Andy

[Oldiebut goodie]

I had a leak through the prongs of the sensor! That was hard to find. If there is liquid sitting in the outside contacts that could have happened.

[Shotage]

Thanks very much.

I've order a new switch too so hopefully that will eliminate that problem also.

Thanks again.

[Shotage]

Hi all.

So today I checked out the dalek top tank, removed the tube and took a peak inside. I was surprised to see it right to the top. So I guess that not much was lost and was replenished from the small top up.

This is hopefully good news, would you agree?

I am 99% sure it has come through where the sensor is and have therefore ordered a replacement sensor.

Do you think I should replace it and just keep an eye on it?

Many thanks for all your help.

Andy

[dsmith1974]

Hi, just had a similar problem. Got the van back from the garage last night after a coolant flush and drain (PO hadn't done one in the last five years!) and noticed a tiny little wet patch under the engine.

Looked like it was dripping off the rear subframe near the exhaust and tracked it back to the pipe that connects the header tank to the expansion tank. Also took a look inside the expansion tank and it was way passed Max (right up to screw cap).

So took another look this morning and discovered that the connecting pipe was actually made of two pipes joined with a plastic insert and jubilee clip (looks like an old bodge job).

I think what had happened was before going into the garage the engine had never warmed up properly due to a stuck or missing thermostat (guage needle never reached the led) and now that's been fixed the systems under greater pressure and the bodge isn't standing up to it.

I guess it needs the pipe replacing first and since the header tank level fell below the top pipe, have it bled again?

Don't think I'll risk taking the van away this weekend. On a plus note the garage fitted a new water pump which was squeeling and had a bit of play.

[kevtherev]

Why don't you just replace the pipe yourself?

it won't need to be bled.

What coolant did your garage use?

[dsmith1974]

Yea, I can replace the pipe no bother, just thought that becausethe level had dropped below the top inlet of the header then there may be air in now? You reckon if I fit a new pipe and top up then we could still go away this weekend?

The garage used 9L of triple qx (red). I left it in the van for them.

[dsmith1974]

Is the cap to tank pipe meant to be two pipes joined? Maybe the diameter on the two tanks is different. That'd be a bit odd though.

[Shotage]

I know this is an old thread, but I thought I should clear up what my original problem was. In fact not a leak at the cap at all, it was a very small crack in the tank itself near to the cap. I replaced the tank and it's been fine. Many thanks, Andy

[majordyRule]

Just saw the final post in this thread and have the same problem: crack in expansion tank just below cap.

Only problem I have is that i'm running an old diesel and the replacement expansion tanks are not cheap: http://www.justkampers.com/catalog/prod ... oC2lnw_wcB" onclick="window.open(this.href);return false;

I know the system is under heat and pressure in use but does anyone have any experience of gluing/sealing a crack instead of replacement?

Cheers