Expansion tank leak? Advice needed

enuff_zed

enuff_zed

Lifer
 Attleborough, Norfolk
Good afternoon all.
Well SWMBO reported a couple of days ago a hissing noise from the left side at the front (heard from within the car). This was after what she referred to as a 'nippy' drive to Tesco. A round trip of about 25 miles.
I couldn't reproduce it and could see/hear nothing untoward.
But today I have noticed coolant on the undertray. Up on axle stands, tray off, and sure enough, it looks wet around the big round connector on the bottom of the expansion tank.
The tank itself looks bone dry, no sign of any leaks at all, just that bottom connector.
So I'm guessing it is the O-ring that has let go at the bottom.
1. Is this easy to change?
2. How? Lift the tank up away from it?
3. I'm planning to change all the seals if the tank has to come out.
4. How much coolant will I lose? Is there a sneaky way to prevent losing too much?
5. Am I kidding myself and should I just change the expansion tank while I'm in there?
6. Is it simple to refill the system? Does it self bleed?
Thank you in advance.

EDIT:
Just seen mention of the possibility of an extra valve/sensor(?) as the car is an automatic. Any pointers on that would help too.
 
enuff_zed said:
Good afternoon all.
Well SWMBO reported a couple of days ago a hissing noise from the left side at the front (heard from within the car). This was after what she referred to as a 'nippy' drive to Tesco. A round trip of about 25 miles.
I couldn't reproduce it and could see/hear nothing untoward.
But today I have noticed coolant on the undertray. Up on axle stands, tray off, and sure enough, it looks wet around the big round connector on the bottom of the expansion tank.
The tank itself looks bone dry, no sign of any leaks at all, just that bottom connector.
So I'm guessing it is the O-ring that has let go at the bottom.
1. Is this easy to change?
2. How? Lift the tank up away from it?
3. I'm planning to change all the seals if the tank has to come out.
4. How much coolant will I lose? Is there a sneaky way to prevent losing too much?
5. Am I kidding myself and should I just change the expansion tank while I'm in there?
6. Is it simple to refill the system? Does it self bleed?
Thank you in advance.
Click to expand...
Change it, not complicated. Google it, there is you tube instructions for the job.
 
Suspected that would be the advice. Not too pricey and it's not a daily so I can take my time.
Not worried about the spannering. I'd like to think well within my capabilities, just thought I'd get the full low down from the experience on here before I started.
Just about to order up a new tank.
On the bright side, a good excuse to be in the garage, not building garden sheds, raised beds, mowing, painting etc. Especially as it's management's car, and she'll be itching to get back behind the wheel.
Will also be the ideal opportunity to fit the sound generator parts I picked up. I am just going to leave the small bit of foam in. That should wake her up :D
 
Best to replace all the o-rings at the same time. My coolant sensor played up afterwards, so for the sake of another few £s might be worth changing that to.
 
ErrErrminator said:
Best to replace all the o-rings at the same time. My coolant sensor played up afterwards, so for the sake of another few £s might be worth changing that to.
Click to expand...

Just ordered a Hella one. For the few quid extra, it comes with a sensor.
O-rings - not supplied with the tank? That's thrown me!
But I do have one of those big cases full of dozens of different sized O-rings, so hopefully that'll solve my problem.

Thanks for the advice :thumbsup:
 
Arguably it might be worth looking at the water pump and 'stat while you've got the coolant system drained too, depending on mileage. Mine was showing no odd symptoms (04 110k) but upon changing the thermostat I've noticed it coming up to temperate way faster, particularly on cold days, so I suspect the stat wasnt closing fully when cold.
 
Well yesterday the new expansion tank arrived. Oddly the Hella label is stuck over the top of a Mahle one, which would have been more expensive. And it did have the O-rings already installed.
As I had the car in bits, waiting for it, I got stuck in straight after work. The old expansion tank lifted straight out quite easily and I can see that the O-ring seals are flattened and hardly protrude from their seats, so hopefully that was my problem.
Then the fun started! As I was looking at the old tank I heard a cracking noise from down in the depths of the engine bay. Turns out it was the original 17 year old plastic housing of the oil cooler thermostat failing under pressure from it's internal spring. It sits inside the lower housing, held in place by the expansion tank and now I'd removed the tank the spring was free to wreck the housing. I guess the plastic must degrade over time.
So the car is still in bits waiting for a new one to arrive, hopefully this week!
I had read somewhere about automatics having this oil cooler thermostat, but didn't follow it up. :headbang: In hindsight I should have bought a spare just in case.
I shall certainly be advising anyone else to do so!
 
You must log in or register to reply here.
Back
Top Bottom