Water Loss?

I'd say this is excessive for the mileage. Check that the carpet inside under the heater is not wet - this will be due to a leaking heater matrix.

Two mechanisms for water loss without obvious leaks are :-

1) Head gasket leak between waterways and cylinder(s) or waterways and oil ways. In the case of the latter, milky deposits (oil/water emulsion) can often be seen on the dipstick. At 900ml per month I'd say this is unlikely to be the problem as the oil level would be rising due to the water.

2) Failure of water pump sealing gland. This is usually the precursor to pump bearing failure and possible cambelt problems. The leak only occurs during full radiator pressure when driving. Leave the car to tickover until the electric fans come on and then look underneath at the front of the engine for any water drops.

I've just had this second problem occur on my 405 1.8 petrol and the bearing was on its way out and the cam belt was very loose. I caught it in time so no damage. Change the cam belt and tensioner whilst you are there. 3rd party parts are not dear but your time/labour will be the very similar whether you do the belt or not.

Bob

Thanks for responding

Cambelt changed 7 months ago. Pressure test by garage reported factory specs.

It's odd because I don't usually lose so much coolent?

Thanks

It's normal practice, in my experience, to change the water pump when changing the cambelt because of the subsequent problems that can occur.

I believe that I have the original water pump.

I've only had to topup twice with about 900mls coolant.

Firstly, after the cambelt was replaced. I assumed that the mechanic had forgotten to topup after removing the head to replace a couple of valves.

Second, 8 months after the cambelt break.

At other times, a few hundred mls periodically.

Bit odd.

I might ask the mecahnic who did the cambelt job to test for leaks - providing any warranty is still in force. I am not very optimistic on this through after 8 months.

Best wishes

S

I would like to put some Radweld into the radiator. I would prefer to introduce this via the expansion chamber. If I do this, will it find any leaks that there might be in the radiator?

Thanks

Ps. Can it be put into the expansion chamber when the system is cold?

I think this Radweld is the liquid form.

Thanks

Draw off a pint or so from the radiator drain into a jug. Add the radweld and run the engine till warm with the cap off. When hotm use the jug to top up to the max level. That way you won't waste good radweld down the over flow.

Bob

Thanks for responding

I am a bit nervous about removing the drain plug.

How about this:

When it gets a bit low, make up a solution of antifreeze/water, add the Radwell to this mix (stir or shake).

Run the engine till it get a little warm (don't see the importance of this, bearing in mind the method). Add the solution, drive as normal, hope it reaches any leaks in the radiator.

Thanks for the advice.

Ps. Someone told me that I can't add Radwell to the expansion tank because it would coat the expansion tank rather than the radiator. Any comments.

Did you mean add the Radwell to the jug mix, or directly into the expansion tank?

Thanks

Can Radweld be put into an expansion tank, neat?

Thanks

Yes put the radweld direct into the expansion tank. The idea of taking the coolant out first is to empty the expansion tank so that your radweld goes into the system. My expansion tank is part of the radiator and only holds a small amount. If you have a separate exp. tank then maybe you will have to draw off more.

What is the big deal with turning the drain c*ck??? Mine is a 90 degree turn and it comes out a 1/4" or so at the same time but cannot fall out.

Radweld is only going to fix small holes in the radiator. It will not fix a leaking pump or a cylinder head gasket problem. The radiator should be dry all over and ends up with a slightly dusty appearance so the any leaks show up as a damp, darker patch which then evaporates often leaving a stain from the coolant additives. it will also steam slightly in cold weather if you have a leak.

Bob

te:

Can the Radweld be added to the expansion tank if it contains water/ coolent. Or must the exp tank be empty?

Thanks

It does not have to be empty but one of your questions was about how well the radweld will get to wherever the leak is. So I thought up this method to help you. There is obviously less water circulation in the tank itself so to get the Radweld into the circulation you need to get it from the expansion tank hence draining some of the existing coolant out.

Are you really sure you have the type of leak that Radweld will cure? if you can't see the leak or the evidence of the leak (other than the waterloss) then radweld is not likely to do you any good.

Bob

A word of caution. If you drain water out of the system (i.e. empty the expansion tank and a bit more) you could run into problems. The 406 has to be topped up using a header tank because parts of the cooling system are above the filler cap and, if you top up just through the filler neck, will remain full of air which is very bad news (overheating bad). Haynes suggest using a large plastic drink bottle with the bottom cut off and inserted into the filler upside down ensuring a good seal where it goes in.

I use a latex glove with a hole cut in it as a makeshift grommet/seal round the bottle neck.