Leaking Coolant

dos30

My E46 is leaking coolant, normally I'd just top it up about 1/2 litre a month. I've had 2 garages look at it, the main dealer replaced the thermostat and housing I think.
Bavarian Autotechnic replaced some other component, can't remember what it was.

However the leak now seems to have got worse, the low coolant light came on this morning and the water temperature hit red on the dial. So now the car is parked about a mile down the road from work.

Can I just fill it with water to get it home, and get it to a garage?
Is coolant just used for its antifreeze properties or is it necessary for sufficient cooling?

MarkR

You should be able to fill it with water, or a mix of water and coolant. Are you seeing stains below the car if it's leaking, or is it boiling off? Is the fan near your radiator coming on?

tmcw

dos30 wrote: »

Can I just fill it with water to get it home, and get it to a garage?
Is coolant just used for its antifreeze properties or is it necessary for sufficient cooling?

If you're topping up, you should probably be topping up with straight coolant. The vapour point of the coolant will be lower than water, so if the coolant in there is diluted out, it will boil away much more rapidly than if you have the correct mix in the cooling system.

voxpop

As markR said - top up with water in emergency - but get some bmw coolant in the motor factors and have a bit(litre) premixed in the boot for top-ups.

Overheating is probably down to air being trapped in the system. If you have a leak then when everything cools, air will be sucked back in. You need to bleed the coolant system.

As for the leaks - check the connectors of the coolant pipes with your hand - feel for drips. Coolant residue will leave a chalky mark - so have a look around for that. If you cant see an leaks from the pipes then, unless its been done, its probably the waterpump leaking - usually you would do the waterpump at the same time as thermostat and housing - but it might have been left out for whatever reason.

A pressure test on the coolant system should highlight any issues with the pipework - though small leaks can be missed.

SilverBell

could be a head gasket too. Check for white smoke at the exhaust. Sometimes smells nice cos of burning coolant.

When my head gasket was on the way out, I travelled with a few litres of water in the boot...just incase. As said already above....better than no coolant.

Another check is to feel the hoses after the car starts. If a head gasket is gone...the coolant system may become pressurised....hard hoses. But hopefully its one of the other symptoms at fault.

DublinDilbert

What year E46? What engine? The system needs to be pressure tested.

Were any of the hoses replaced when the other parts were changed? The o-rings become brittle and once the system is opened don't seal correctly.

I'd be one of the o-rings is weeping. You can buy the o-rings in the likes of abbey seals for €0.5 each, or pay BMW €40 for the hose

Also check the L-shape pipe at the back of the engine, if its leaking the water will run down the bell hosing away from the engine and is very hard to spot some times.

dos30

DublinDilbert wrote: »

What year E46? What engine? The system needs to be pressure tested.

Were any of the hoses replaced when the other parts were changed? The o-rings become brittle and once the system is opened don't seal correctly.

I'd be one of the o-rings is weeping. You can buy the o-rings in the likes of abbey seals for €0.5 each, or pay BMW €40 for the hose

Also check the L-shape pipe at the back of the engine, if its leaking the water will run down the bell hosing away from the engine and is very hard to spot some times.

It's a 2001 318CI 1.9l, I've no idea if any of the o-rings were changed. I'll have a look at the parts list and post back after lunch.

giant_midget

The PC people will probably disagree with this but it worked for me a few years ago...crack an egg into your rad the egg will boil and it will seal the leak (depending on how big the leak is)

voxpop

jesusinaglanza wrote: »

The PC people will probably disagree with this but it worked for me a few years ago...crack an egg into your rad the egg will boil and it will seal the leak (depending on how big the leak is)

Even if that works - its a temporary fix at best. Better to find the source of the problem and sort it out. The coolant system isnt the best but is pretty easy to work on

danjo

Could also be the plastic expansion tank. A pin hole in this will leak coolant under pressure. Check when the engine is hot.

dos30

danjo wrote: »

Could also be the ploastic expansion tank. A pin hole in this will leak coolant under pressure. Check when the engine is hot.

Ok I filled it up there over lunch, it took 3 litres of water and 1.5 litres of coolant, not a good sign!!

There seemed to be dripping coming from the bottom of the expansion tank. It was raining though and couldn't see under it so I can't be sure. I'll get it off to a mechanic after work and hopefully he can sort it.

nogoodnamesleft

Might be worth your while bringing the car to a mechanic for a pressure test to identify where the leak is coming from.

dos30

Turns out it was the expansion tank, there was a crack on the side of it.
Got a new one fitted on Saturday but when I collected the car from the mechanic there was a warning light on the dash.
Looked it up in the manual and it says
"Engine Exhaust emission values have deteriorated"

Anyone know if this would be a result of the car overheating, or could the mechanic have knocked out some sensor while fitting the new tank?

electrofelix

Connected to your oxygen sensor. Could also be due to a hose around the intake expiring and letting in unmetered air which is affecting your fuel/air mixture in the engine. Don't think any of the air/fuel hoses would be close enough to be affected by replacing the expansion tank.

Given that you were loosing coolant and hit red, I'd be concerned that you have a head gasket issue, and the coolant has leaked through and destroyed your oxygen sensor.

I'd keep an eye on your coolant level over the next few days. If it continues to drop, then its likely that the expansion tank crack was due to overheating or excess pressure in the coolant system.

It could well be that it's entirely unrelated in the end and you oxygen sensor just happened to go as well, but keep an eye on your coolant level anyway.