Indie will carry out a head test in the new year, but gas any one any other ideas about the cause ?

All seem agreed the cause is a failing head gasket. So not much point in doing an expensive investigation which might well give you a false negative result if the leak is tiny.

If I were you I would try retorquing the head bolts if you can get at them. Might help, and nothing to lose by doing so if the head's got to come off anyway.

You are probably right, A-T, I had assumed they were normal bolts in an old car. However, I would risk cracking them undone one by one with my old crude bar torque wrench, noting its starting position, observing the torque needed when retightening back to starting position then if this is less than 60 ftlb (mine's in old units) continue till it is, or stop if it feels as though going to shear.

www.freeasestudyguides.com/a1_4.html

I think it unlikely that they would shear at this level which is enough for a good squeeze - almost what is needed for our Focus wheel bolts. Of course, the OP could gamble 16 pounds on a new set and torque them in as per Peugeout instructions. I have no idea whether they can be removed without disturbing the cam - no doubt others can advise....

.... have you considered the coolant pressure cap?

Read all the posts above - it seems the pressure cap has been checked for coolant loss, but one never knows ....

Prefer not to use Radweld until it is vitally imperative.

I'm not sure how effective Radweld is for leaks inside the block. I thought it was more suited to radiators (hence the name :-) ) or heater matrices or other places which don't get as hot, or suffer pressure differentials? And there are all the old stories about mustard, porridge oats and other k^tch^n items being just as effective ....

But wouldn't it just smell of antifreeze/coolant?

Just realised the car heater / air con gives off a smell of stale water, sort of musty, when it first starts in the morning. Tried everything to sort it , air con bomb, new pollen filter , heater full on before switch off with no improvement. But could a leak in the heater matrix be causing the smell and the coolant leak?

Although I have owned a 207 for nine years I don't know the exact location of the heater matrix. In older Peugeots it was tucked away under the centre of the dash, and any leaks became evident with a puddle, usually in the passenger footwell. As you have been topping up the coolant regularly I would have thought that would not be musty, so any mustiness may be coming from under the carpets. Try looking there (that'll be fun :-( ) though from your account you have lost a lot of coolant, so it must be escaping somewhere or any puddle would be quite noticeable?

Air-con is often a source of odd smells, so have you checked the intake vent in the scuttle in front of the screen for leaves or other fallout?

Just a long chance Andrew.

Not sure where to go from here but to wait until it gets worse.

How do you do that Gibbo

Is it possible to retro fit a coolant level sensor similar to the one used in the K series engine to stop it overheating?

But what are the consequences of taking the car on a long high speed journey with this undiagnosed fault ?

I have only limited experience of head gasket failure. That example was with a 20-year-old 205, and the symptom was traces of oil appearing in the coolant overflow tank, though the usual test had proved negative. The leak was so slight that there seemed very little risk of sudden failure, I had the head skimmed to preserve a cherished vehicle.

It sounds as though your HG is letting cylinder pressure into the coolant galleries. Again I would take a chance against sudden failure, but I might try to avoid vigorous driving, but overheating seems less likely at this time of year. If the HG were to fail suddenly I guess there would be a visible escape of steam, but there should be an indication on the temp. gauge first. Not likely to kill the engine IMHO.

If you take the cap off and rev the engine, can you see bubbles?

or maybe, try looking under the engine , when it's hot)
in pitch dark with a torch's pencil beam to see any wisks of steam from anywhere in the engine bay.

Also, a uv torch from ebay £2 would show the fluorescence of any leaking antifreeze?
www.ebay.co.uk/itm/9-LED-Mini-Aluminum-UV-Ultra-Vi...Y

Well, I never, you can buy kits with glow in the dark liquid for easier detection
www.amazon.co.uk/Torch-Detection-Cooling-Antifreez...4

Cheers
Liam

Edited by liammcl on 08/02/2018 at 01:21

Got a second opinion from an ex recovery bloke who tested the cooling system, pronounced it ok and then found the leak from the water pump area. Obviously the leak takes place when the car is moving and the coolant must spread under the car with none on the floor when stopped.

Good news if this is the correct diagnosis. But water pumps are usually changed with the cambelt - when was that last done? It may not have been at that age and mileage, but if you are changing the water pump, may as well do the belt at the same time. The jobs require similar dismantling and reassembly.