406oc.co.uk

Just came across this forum, wish I found it a few weeks ago!

Right then, this is the problem.....

Bought the above vehicle a couple of weeks ago, only has 67K in the clocks and is in "as new" condition for a good price. Driving it around for about a week and the coolant light came on. Got home topped the expansion bottle up and went back out. Drove it to work the next day and guess what, coolant light came back on......

Topped it back up, checked for an airlock, vented the air from the 3 locations, sat it at idle on the drive until she was hot and put the cap back on the bottle. Took her for a blast, got home and checked her out.... This is when I notice the top coolant pipe is rock solid and very hot so I let her cool down, took the lid off the expansion bottle and water pi££ed out over the top of the bottle....bad news...

My first thoughts were it's either the expansion bottle or cap which I have changed, as the water is coming out of the release valve in the cap, but this hasn't cured it.

I have left her at a garage today to have the head gasket, timing belt etc changed. My question is from what I have described would your guess be the same or is there something else that is a known problem on a 406 HDI that would cause the same symptoms that won't cost me am arm and leg to repair.

Thanks for any help/suggestions.

Mark

309gti wrote:This is when I notice the top coolant pipe is rock solid and very hot so I let her cool down, took the lid off the expansion bottle and water pi££ed out over the top of the bottle....bad news...

Haha been there, done that... It's normal. Think about how when you put a half-full 2 litre bottle of water in the fridge at room temperature and when you pull it out, it's 15c colder and the bottle's crumped up due to the contraction of the liquid. The same thing happens in a cars cooling system, albeit the other way round. Even lukewarm coolant can knock the cap out of your hand when try to take the cap off

My first thoughts were it's either the expansion bottle or cap which I have changed, as the water is coming out of the release valve in the cap, but this hasn't cured it.

Normally, you'd fill the expansion tank until it's full (park the right hand side on a kerb, as the expansion tank isn't the highest point in the cooling circuit), run the engine until the thermostat opens and the water level suddenly drops, top it up again then slap the cap on. When you're out driving, the excess liquid will come out from the cap and you'll end up with the correct level in the system.


If your coolant light is coming on you've got a serious leak. Chances are it's either the radiator or where the bottom hose meets it. Look for coolant-coloured patches on the radiator/fittings (easiest when using Halfords 'advanced' coolant - it's bright orange, but flush the system with plain water before using it). You may also notice other drivers exhausts are a bit smokey when you pull up behind them at lights - that's you, that is...

Radweld works well, but be aware you need to re-add it if you change/refill the coolant.

Hmmmm, thanks for your reply.

I have spent ages looking for any sort of leak from the radiator, pipes and bottle and the only place it seems to be leaking from is over the cap of the expansion bottle.

I really am at a loss now!

Oh, forgot to add.....

The coolant light only comes on after a good run my journy to work it 30 miles and about 45 mins and it's only after this the light comes one. I can rum it round town for a couple of days and check the level and it only need topping up slightly. Seems to only be loosing water once it's upto pressure, no constant drips from anywhere

The return of the rock-hard hosed, coolant losing, HDi's eh?

This happened to James on here and was indeed the head gasket. The garage will be able to "sniff" the expansion botle for this anyway also worth considering the condition of the rad too. Oh and make SURE they chage the water pump whilst doing the cambelt!

Cheers for the advise! I'll give them a call and tell them to.

Mark

309gti wrote:the only place it seems to be leaking from is over the cap of the expansion bottle.

If the fluid level's high enough to be leaking from the cap, it'll never trigger the low coolant light, which only comes on when you're virtually dry.

Seems to only be loosing water once it's upto pressure, no constant drips from anywhere

You're losing the coolant as high pressure steam, likely from a virtually invisible hole in the radiator, not as water droplets, although you might be able to open your bonnet a few hours after a long drive and see a small amount of fluid on the undertray if you have one (otherwise, can you park the car over some paper/cardboard?

Sounds like the engine is pressurising the system, in which case it would be head gasket. Over time and if the coolant hasn't been changed every 2 years, it will rot the head gasket, along with the radiator and hoses. It's very much a false economy to not change the system. Coolant is as much about anti-corrosion as much as being an anti-freeze, except the anti-corrosion chemical part depletes over time and needs to be replaced. A garage will pressure check the system quite cheaply for you, to either find an external leak, or just a pressure drop indicating a head gasket problem.
It may be worth changing you expansion bottle cap first of all, since they are cheap to replace.

Either way sort the problem out quickly since if it is an head gasket problem it will get worse and may cause many more really expensive engine problems ie wear of the bores due to water washing the oil away (metal to metal friction is not good!).

I have already replaced the bottle and cap, this didn't solve the problem.

Fingers crossed the problem may have been found, will post back later if it is what the garage say it is....I hope so as it will be a fraction of the cost

muffindell wrote:Sounds like the engine is pressurising the system

The engine temperature pressurises the coolant system - it's normal operation. Take any car for a drive, remove the expansion tank cap and a jet of boiling coolant will rip the cap out of your hand. Listen to the voice of experience

Actually it's the water temp that pressurises the system (hot water expands) in a normal situation.

I don't actually open it when it's hot, I leave the car to cool first! But there is still a lot of pressure behind the water which makes it come out

Which would suggest that there isn't an external leak, otherwise the pressure would drop quickly.