Hi,
I have a problem with my car, specifically a 2014 Ford Focus MK3 1.6 TDCI. It's like I'm losing coolant somewhere, and I have no idea where.

Overall:
1. The thermostat was checked and replaced twice - the temperature gauge was acting up, and unfortunately, it's still acting up.
2. The system was tested for leaks under pressure for three days - it held pressure.
3. Leaks were checked using a UV dye - no UV traces.
4. We checked the lines and saw no visible leaks - none.
5. The reservoir cap was replaced, and as a result, the entire reservoir and cap were replaced - the previous one was leaking from the bottom.
6. The UPG test was performed four times, with negative results each time.
7. No oil under the oil cap.
8. No sweet smell in the car/film on the windshield.
9. No exhaust smoke or any mist when the engine is cold.
10. The system has been bled several times.
11. The EGR cooler is tight.

The engine runs smoothly after starting, there are no problems with starting, it doesn't overheat, or anything. The only issue is the coolant loss. The problem is that when I start the car in the morning and drive it for a while, the coolant level in the reservoir slowly rises. Then, as the car warms up, the system draws all the coolant from the reservoir. If I bleed the car, it's fine until I turn it off and let the engine cool down. I bleed the engine until the air stops leaking and the coolant stops losing.

The car has been to six garages. Unfortunately, five of them couldn't find the cause and firmly ruled out the head gasket as the culprit. One said it was the head gasket because they couldn't think of anything else. I bought the car five years ago and it runs just like it has from the start, except I'm losing coolant. They quoted me around 8,000 PLN (2,000 EUR) for head gasket repair, but they're not sure that's what's wrong.

Does anyone have any ideas what might be wrong?

 

Since we have to start somewhere,
Please, explain exactly what you mean ,, the temp gauge is acting up .


Do you know if the system was pressure tested ,warm or cold ?

How long has this been going on ? Were you using the heater, at the times the coolant was dropping ?
Some things we can diagnose over the net and some things we can only suggest., but lets see what we have and obtain as much info as possible.

 

The point is that the gauge reaches operating temperature, then drops completely down, as if the car had been turned off, and this happens several times. I've had this problem with my car for a year and have driven almost 15,000 kilometers. As far as I know, the car was tested cold. Generally, regarding the heater, the problem is the same whether I have the blower on or off.

 

If no other dash gauges have been affected, suggest you or have someone check the connection at the coolant temp sending unit or the sending unit itself.

A faulty water pump seal will allow air to be pulled into the cooling system and that will force coolant out too, but it will dry before anybody sees it.
Did anybody check the oil to assure coolant is not going into the lubrication system ?

 

In my case, it's like this: when I start the car cold, the fluid level slowly rises until it starts to overflow. As the car warms up, it draws fluid into the system until the reservoir is empty. Another issue is that when I start the car cold with the reservoir empty, after a few minutes there's a lot of fluid in the reservoir. This looks like a faulty water pump to me.

The oil cap is spotless, with no oil buildup.

 

What about the OIL LEVEL ?

 

The oil level is within the minimum/maximum range and the cap is clean.

 

If the motor oil doesn't appear soupy, the coolant is either going somewhere else , or there is a lot of trapped air in the system.
How were you./ mechanic removing trapped air from the system ?
Important to know this !

 

Coolant level is low in the tank doesn't mean it's running low or loss. According to what said, there is no internal (head gasket or cracked cylinder head/block) or external leak, coolants are circulating within the system just that they are in the inappropriate location.
You said you changed to a new reservoir tank and its cap, how about a new radiator cap and pressure test?
If you think there is something wrong with the gauge why don't you hook up a scanner a see what you get with the ECT? How many ECT are there in your Focus?
If you have trouble bleeding why don't you use floor jack and jack stands and elevate to the position where the cap is so that it sits at the highest point of the system, it's easier to bleed it this way with success.
It seems like you've been heading to the wrong directions.