The car is a 2007 1.8Desiel and trying to figure out if this is a simple problem or major one...

The coolant in the car seems to disappear randomly, I check it on nearly every drive and most of the time it's fine but occasionally it empties the entire tank.

There is no visible leaking anywhere so doesn't seem obvious where this water is going. When accelerating hard white smoke does come out of the exhaust but not vast amounts, just enough that you can see it in the headlights of other cars. Not noticed this during the day.

There is no water in the oil (i.e. no white emulsion on the dipstick).

The other weird thing is that the temperature gauge randomly goes from normal temperature (~80 degrees) to 0 and back and forth say every 10 minutes. It appears that allowing the car to slow down brings the temperature gauge back to life more often than not but that might just be me trying to find order in randomness.

Has anyone else experienced this before and have any pointers? I've been told it's a water pump or head gasket issue. The headgasket I would have though it would always lose water but perhaps this is not the case?

Any help or advice really appreciated.

Thanks,

replace the coolant tanks cap, that is a common place as the steam pressure builds up and disperses fluid.

Also check your thermostat housing and see if you can feel any moisture around there. I had the same issue recently and had this gasket replaced and it drastically improved the loss rate.

Many thanks for this, funnily enough I've just changed the coolant reservoir plastic cap this week as the last one seemed to weld itself on and I had to rip it off with pliers and screwdriver which totally mangled it.

I'm convinced the water is getting super heated and causing pipes to burst and the cap to weld on. A couple times this year I've also had coolant pipes burst as I expect the heat/pressure stressed it beyond their operating limits.

I can't help but feel like the cause is the water pump packs up, the water in the engine superheats quickly, boils off/cavitates around the temperature sensor hence nothing to measure so it starts reading 0 until the water pump starts working again and fresh coolant replaces the air.

If I rev the engine to around 3000rpm put it in gear and release the clutch to do engine breaking that seems to more often than not make the temperature gauge spring back to the normal 80/90 level. This may just be a red herring as I've tried to find some order in randomness but feels comforting to believe I found something that works most of the time ;)

I've got it booked into a garage next week to see if they can find out what it is. I'm keen to get the water pump changed just in case this is it but given I know very little about cars I may well be throwing money at the wrong problem... how likely do you think it is the water pump that could cause symptoms like this?

My suspicions are moreso based on a bad thermostat and the fact you have already replaced the cap.Hopefully its not too expensive!

I'm having simular problem with my 07 S-Max. Ford gave my coolant tank a pressure test to see if I had any leaks but passed it so they recommend I changed my coolant tank incase it had shrunk and the cap wasn't fitting properly. I had this done yesterday. On my way to work I noticed the temp starting to climb, when the car had cooled I checked the level to see it was almost empty AGAIN!! Please help!!

Could be the tank has leaked. Check it over for any potential cracks or slight splits. I had this issue in a car previously. Slight crack in the wall and that expanded and leaked.

It seems weird that the same thing is still happening even tho the new tank is not even 24hrs old.

Tank or cap?

Ford replaced the tank.

Check the cap as they do fail.

Surprised that Ford didn't change the cap at the same time.

Tightwads.

That does surprise me but at the same time doesn't.

Ok thanks! Please tell me this is nothing to do with the head gasket! The cars only done 88,000.

Nah most likely just the cap that goes over the coolant reservoir. Shouldn't be the gasket...

That's good!! She's not giving any other signs and still drives lovely. Apart from losing this water you would know anythings wrong.

Yeah mate at work had the same issue. Replaced the tank but not the cap and same issue then replaced the cap and it was working again.

Fingers crossed then!! Someone mentioned placing a plastic bag over it then putting the cap back in place for the meantime, would this help until I can get a new cap after the bank holiday weekend?

It would help in a way as it will help to slow the escaping gasses

Hi I'm have same problem the car lozenges water and overheating I change water pamp and I change thermostat and again lozenge water and overheating can you tell me what is the problem 

Having same issue with my 07 s-max seems to be a common fault. Mines in garage now as was over heating, checked water and it was empty so filled it and straight away it leaked out straight from underneath the car, been told water pump but they're calling me tomorrow so I'll update when I hear from them

Anyone’s car also over heat all the time?! We’re convinced there is an air lock. It’ll over heat and water will come out of the header tank and then the temp will drop until the air lock it there again? Replaced the pipes, and thermostat and the egr as a garage had bodged a lot of work before we bought it. 

On 6/7/2020 at 5:09 PM, Cleo said:

Having same issue with my 07 s-max seems to be a common fault. Mines in garage now as was over heating, checked water and it was empty so filled it and straight away it leaked out straight from underneath the car, been told water pump but they're calling me tomorrow so I'll update when I hear from them

Hi do you have a update on how you got on please i had to get recovered today and car is at the garage now dreading the news hoping its not to major thanks 

We have just had our 09 smax in garage, serious overheating, garage said the pipe from the header tank to engine was blocked, charged £117 to clear it but now we are having to fill with water twice a day, got no leaks, oil in engine is fine, temp maxing out and cutting engine out, its a living nightmare as need car daily, where is the water going, also, changed the cap on tank as like other poster it welded itself to tank...any help????

Almost certainly a faulty thermostat.

Before spending vasts amounts of time and money change the thermostat they are cheap and easy to replace. (check your model it may have two thermostats fitted).

When you do get the problem fixed please remember to refil the system with at least 50% Ford coolant

Anybody found the cause for these problems as mine is doing the same I replaced everything now thinking water pump

Hi, 

I have the same problem, I have a 2010 smax 2.0ltr petrol 

unsure what the problem is I’m losing water. I have replaced the header tank the cap and also replaced the water pump. Still have the issue. Checking water daily and it’s always down on the level I leave it on or sometimes it’s all

gone and then overheats. Help please? Unsure what to do. I also sometimes get the smell of fumes in the car which is not nice. 
 

Can anyone help? Advise?