Car: 2013 MK3 Ford Focus 1.6 TDCI

I've been having an issue with my temp gauge for a while. Car gets up to temp with no issues what so ever. Then a short while after that the gauge will drop to the quarter mark and make its way back to the middle (normal). It will just stay there after that. No overheating, no loss of coolant, no leaks etc. 

Also, if i turn on the heaters to a high heat the temp gauge will drop completely but it has never done this before. Its probably worth noting the radiator went and i had a new one fitted, these issues arose and then i suspected the thermostat so i changed that to find it was stuck open. Before the rad went i never had any issues what so ever. 

It may be something i have to live with but the fact it hadn't happened before makes it so annoying to see happen and makes me seem something is a miss. 

 

Any help would be great. 

Could be an air lock in the system. 

Do you get heat coming out of your heater vents when put on hot? Had a few of these not heating up or random gauge issues and its ended up being either the head gasket, cylinder head or block issues. The only common issue is they get no heat through the vents. Usually the coolant is a funny colour and there's back pressure in the coolant reservoir too. Hope this helps. 

5 minutes ago, MasterTechTip said:

Do you get heat coming out of your heater vents when put on hot? Had a few of these not heating up or random gauge issues and its ended up being either the head gasket, cylinder head or block issues. The only common issue is they get no heat through the vents. Usually the coolant is a funny colour and there's back pressure in the coolant reservoir too. Hope this helps. 

Yes i get really hot heat when on full, its practically a sauna lol. I used one of this combustion test using the blue liquid that goes in the coolant res and it stayed blue. I believe these are pretty accurate. 

My worst fear is a head gasket, head or block issues. Hoping it's not but not sure. Do you suggest anything? Any specific test that can be carried out?

 

4 hours ago, LG1996 said:

Yes i get really hot heat when on full, its practically a sauna lol. I used one of this combustion test using the blue liquid that goes in the coolant res and it stayed blue. I believe these are pretty accurate. 

My worst fear is a head gasket, head or block issues. Hoping it's not but not sure. Do you suggest anything? Any specific test that can be carried out?

 

Check the coolant isn’t a funny colour to begin with. 

34 minutes ago, Hooded said:

Check the coolant isn’t a funny colour to begin with. 

Coolant doesn't seem a funny colour to me.

15 hours ago, LG1996 said:

Yes i get really hot heat when on full, its practically a sauna lol. I used one of this combustion test using the blue liquid that goes in the coolant res and it stayed blue. I believe these are pretty accurate. 

My worst fear is a head gasket, head or block issues. Hoping it's not but not sure. Do you suggest anything? Any specific test that can be carried out?

 

I wouldn't suspect anything along the lines of head gasket or block issues then. Those liquid tests are only accurate if exhaust gases are leaking back into the cooling system but are a pretty good indication none the less. Only other thing I can think of is air lock that's already been mentioned but it's weird it hasn't bled out yet or possibly your thermostat seal is leaking and giving you issues? Could also be a faulty coolant temperature sensor? Just educated guesses at the moment haha

7 hours ago, MasterTechTip said:

I wouldn't suspect anything along the lines of head gasket or block issues then. Those liquid tests are only accurate if exhaust gases are leaking back into the cooling system but are a pretty good indication none the less. Only other thing I can think of is air lock that's already been mentioned but it's weird it hasn't bled out yet or possibly your thermostat seal is leaking and giving you issues? Could also be a faulty coolant temperature sensor? Just educated guesses at the moment haha

I'd like to think there's no air in it as its been a while since and ive done the old trick of cap off and ran it up but who knows. Trouble is when ive done that with heater on full the temp gauge doesn't get off bottom but car heats up. It's kinda like it's in reverse, heater on temp gauge drop, heater off temp gauge at normal. To add to it, when im driving at speed on motorway (70mph) the temp gauge gets to temp and stays and doesn't do the mentioned drop. It isn't half annoying. It only seems to happen the one time and then is fine when im driving on normal 40mph roads, possibly something to do with engine working more at high speed? Recently did a 250+ mile round trip and it drove a dream, no issues whatsoever.

This is strange haha, was the rad and thermostat you fitted genuine or aftermarket? Just thinking if the thermostat opens too early it could potentially cause this, also if your radiator is bigger it will be more effective and cool the engine a bit too well?

21 minutes ago, MasterTechTip said:

This is strange haha, was the rad and thermostat you fitted genuine or aftermarket? Just thinking if the thermostat opens too early it could potentially cause this, also if your radiator is bigger it will be more effective and cool the engine a bit too well?

I had the rad done at a local garage but yes i was aftermarket one and i did the thermostat which was also an aftermarket one. Ive been in the same position thinking its a strange one for a while. I wonder if you're right with it opening too early which causes it to cool and makes the gauge drop. Unsure what effect that would have on the heater side to it make it drop more with heater on? 

I've read that with the TDCi Mondeo, there is an issue using aftermarket 'stats and the sealing rings which  are too thin and cause the coolant to flow past the stat. Oem sealing rings are supposedly much thicker. Don't know if this is your issue. 

3 hours ago, nicam49 said:

I've read that with the TDCi Mondeo, there is an issue using aftermarket 'stats and the sealing rings which  are too thin and cause the coolant to flow past the stat. Oem sealing rings are supposedly much thicker. Don't know if this is your issue. 

Well that's useful to know! Reckon going to ford and buying a oem seal would be worth giving a shot? 

11 hours ago, LG1996 said:

I had the rad done at a local garage but yes i was aftermarket one and i did the thermostat which was also an aftermarket one. Ive been in the same position thinking its a strange one for a while. I wonder if you're right with it opening too early which causes it to cool and makes the gauge drop. Unsure what effect that would have on the heater side to it make it drop more with heater on? 

By putting your heater on full it's directing all of the air flow constantly on your heater matrix to give you as much heat in the car as possible... Effectively acting as a second radiator in your position. 

Also the new seal could be worth a shot seeing as they use the same engines, the seals are pretty cheap and you can replace them without disconnecting all the hoses and such if you fancy doing that. 

3 hours ago, MasterTechTip said:

By putting your heater on full it's directing all of the air flow constantly on your heater matrix to give you as much heat in the car as possible... Effectively acting as a second radiator in your position. 

Also the new seal could be worth a shot seeing as they use the same engines, the seals are pretty cheap and you can replace them without disconnecting all the hoses and such if you fancy doing that. 

I get that and i understand the whole if its overheating do that and put windows down. However, before any of this happened, this scenario never happened which makes it even more so odd. 

I think i may give the gasket idea a shot. Glad i don't have to take hoses off etc and its a pain to get to the back ones. Awful thermostat too compared to the older style! 

did you get any answers to your problem my 1.6 tdci 2014 focus has just started doing the same thing 

Just to be clear - are your symptoms EXACTLY the 'same thing' as the OP?