Hi guys, totally new to owning a car and maintaining it so forgive the stupid question!  My coolant always seems to be below the minimum mark and I'm sure there's a slow leak somewhere, but I've never seen anything on the ground.  1L probably lasts 2-4 weeks and I do about 1000 miles a month.  Looking at previous posts, radweld, k-seal or similar seems to sort the problem out but I can't see where to add it to as there's no radiator cap!  Any ideas?  It specifically says not to add it to the reservoir.

Thanks in advance!

You don't...  It's really not a good idea and can cause more problems. 

But if you do want to add some, the reservoir would be the only place to put it.

What sorts of problems can it cause?  I don't really want to be putting in a bottle of coolant a month, but I'm sure it would be quite pricey to get someone to check over the whole system for this tiny leak!

8 minutes ago, retropedro said:

What sorts of problems can it cause?  I don't really want to be putting in a bottle of coolant a month, but I'm sure it would be quite pricey to get someone to check over the whole system for this tiny leak!

It can't specifically find leaks and block only those, so can end up also blocking important waterways through the engine as well as blocking the radiator or heater matrix.  Worst case scenario is that the engine can no longer be cooled properly, it overheats and either warps or cracks the block, needing a whole replacement engine.  That'll be much more expensive than having the leak diagnosed and repaired in the long run.

You can probably find the leak yourself, just follow the pipes around looking for any sign of dry coolant.  The radiator, thermostat housing and oil cooler would be where I'd focus the checks on this engine.

 

I've tried K-Seal twice, one was a complete success (total HGF in a Rover 200 with oil/coolant mixing, cured by adding K-Seal to the reservoir) and the other didn't do anything (Volvo V40 with no signs of a leak but dropping below the minimum mark like yours).

Amazing thank you both - I'll give it one go and if there's no success I'll bite the bullet and take it in.  Did you add it to the reservoir when it was full or at the low mark?

11 minutes ago, retropedro said:

Amazing thank you both - I'll give it one go and if there's no success I'll bite the bullet and take it in.  Did you add it to the reservoir when it was full or at the low mark?

If you do use it (and I'd still use caution as the cars I used it on were a lot older and worth next to nothing) then I think you just add it to the reservoir when there is space to do so (I.E. when it's low) but I'm sure when I used it the first time they recommended draining some coolant so that you could dilute it with 1l of distilled water then add in that state so it would circulate better. 

Basically best bet is follow the instructions on the bottle but adding to the reservoir instead of the radiator as they instruct.

Just an update - looks like the new version of k-seal goes straight into the reservoir!

 

https://www.youtube.com/watch?v=Zaqxp9_WwB8

I don't like additives but modern sealer should be OK as it only sets when it comes into contact with Oxygen in the air. Have you checked inside the car for leakage from  the heater matrix.

1 hour ago, billyboy said:

I don't like additives but modern sealer should be OK as it only sets when it comes into contact with Oxygen in the air

Which is fine unless you've got an air lock somewhere...which is highly likely after a leak...

 

Eek what will happen if i get an air lock?  Overheating?  It's so strange, but even when the expansion tank is almost empty it never seems to move above halfway on the temp gauge.

27 minutes ago, retropedro said:

Eek what will happen if i get an air lock?  Overheating?  It's so strange, but even when the expansion tank is almost empty it never seems to move above halfway on the temp gauge.

The sealant reacts with air so if there's an air lock (bubble) inside the system it'll start to block/plug the pipe there.  Either causing a direct blockage or causing a lump of sealant that will move through the system and get stuck in a smaller pipe in the radiator or matrix instead.  It's clever stuff and a good idea in theory, but not totally fool-proof lol. 

Airlocks on their own can cause overheating or hot spots (one area hotter than another, causing the metal to warp) so it really is worth repairing a leak rather than just endlessly topping up.  Fortunately the 1.6 TDCi doesn't run hot like the EcoBoosts do, so you have more chance at getting away with a leak on these.

It really is up to you, lots of people use sealants without issue...but not everyone does, it's not worth the risk to me, it might be to you.  

Hello all, just a quick update - I ended up going with K-seal as it was only £9 on ebay.  Used half a bottle as the coolant capacity on the fiesta is quite small (they had guidelines on the bottle), but had no problems since after about 1500 miles and a couple of long journeys of 200 miles.  Thanks again for all your advice!

 

Edit:  PS the bottle now tells you to put it straight into the expansion tank, so no trouble there.

5 hours ago, retropedro said:

Hello all, just a quick update - I ended up going with K-seal as it was only £9 on ebay.  Used half a bottle as the coolant capacity on the fiesta is quite small (they had guidelines on the bottle), but had no problems since after about 1500 miles and a couple of long journeys of 200 miles.  Thanks again for all your advice!

 

Edit:  PS the bottle now tells you to put it straight into the expansion tank, so no trouble there.

Good to hear!  As I said that can work miracles but it is a gamble, looks like it paid off for you