I am losing coolant but no leak. No EML and no sign of engine overheating on dash. But last week the car started juddering as if in wrong gear or there was sugar in tank. 

I have had the coolant tank replaced twice in last 3months and o2 sensors charged. I've placed injector fluid in to see if it would solve the problem. 

Is it safe to still drive? Can't get it in to garage until 2 weeks today. Any advise is much appreciated. 

@RayC333 can possibly best advise on this.

Could be head gasket failed, or cracked cylinder head.

48 minutes ago, Rhianlesley said:

Is it safe to still drive?

I'd say it is probably not a good idea to continue using it until the fault has been found.

On 5/26/2023 at 7:28 PM, RayC333 said:

So, it irked me that my prep for leaks didn't find a crack or other problem before I re-fitted the cylinder head. Out of interest I thought I'd try and find out why.

I found that the static water leak test I previously dreamed up was and is far too slow to notice a leak into a much larger coolant passage volume. I can now see a slight drop in water volume after waiting 24hrs but even then it's not as conclusive as I would like.

Using bits and pieces from around my home I have now rigged up a better test, albeit still Heath Robinson. Nevertheless, take a look at the pics and video I've just taken with a bit of mains water pressure.

Took a while to decide whether to post here or in Have  a Laugh 😁

 

Case study: No sign of any leak, water pump, pipes, coolant reservoir etc.

Poor running, gradually getting worse but no actual overheating or high temperature shown on the dash gauge.

Could if course be a head gasket breaking down, and there is a test kit for that, but there is another possible cause.

1.0 Ecoboosts are known to get a crack in the cylinder head. The design incorporates an integral exhaust manifold and cracking can occur between the coolant passages and the manifold (insufficient wall section and/or poor heat treatment during manufacture).

Result, coolant in the cylinders, most prominently no 2. 

Remove the coils and spark plugs, do a check for coolant ingress - use an endoscope or a simple tightly rolled piece of kitchen paper poking down to the piston crowns. Is it wet?

A head gasket can be replaced but is an expensive job. Both the heads I've worked with also required skimming.

Good luck.