I’ve scoured the internet but not seen anyone explain this. I’ve checked the manual and it doesn’t clarify much either. I could just be an idiot, which is usually the case so apologies if I’m just missing something.

I’ve had a coolant leak for a week or so, I finally got time to investigate and noticed a loose pipe with crystallised coolant on it and a clip that’d slipped down the pipe. Problem solved, right?

well, I’ve been topping up the reservoir with coolant as the leak has been pretty minor and after securing the pipe, I took it for a drive to get it to temp and then check for any leaks once I got it home. On said drive, the car completely overheated (almost in the red on the engine temp dial). I pulled over, shut it off and let it cool before driving home (I was less than a mile away).

I can’t see any leaks but I heard what sounds like liquid dripping after getting home but my driveway is elevated so I can’t jack it up to take the tray off the bottom to check. I wondered if the reservoir was just an expansion tank and that the coolant I’ve been putting in there has just been getting spat out, but then I noticed the radiator has no cap.

Where do I add the coolant? I’ve flushed previous cars and they’ve all had caps on the radiator to fill but this LS just has a square like thing on top that doesn’t look openable…

any advice would be much appreciated

 

I'm not sure if UK models are different in some way, but it's rather easy to find once you remove the plastic intake cover.
Once you've filled and bled the system, fill the reservoir about 3/4 and watch it for a week or so.
Don't become a slave to the level marks on the reservoir.
The coolant will find its level in the reservoir after a few days of driving.
As long as it's never completely empty you're fine.

 

Take a picture of the top of the radiator so we can see what you are talking about.

 

not my image but this is from another forum and mine looks identical (in the UK). The only other forum posts I see mentioning radiators are US/Japan models that have the radiator cap and expansion tank close to one another. I can take some pics of mine to show the whole thing and where the expansion tank is when I finish work

 

UK cooling systems are only filled via the Reservoir.
There is a screw-plug at the top of the rad but I believe it is there so testers can fit pressure testers.
https://i.ebayimg.com/images/g/OOIAA...5/s-l1600.webp
You can unscrew that bolt from the top of the rad, but don't do it when the coolant is hot.

If the coolant reservoir is at the Full mark (check the level by removing the Reservoir cap and dip a stick into it) and it's still overheating then you have a failed water pump or possibly a Thermostat that is stuck closed.
However, the most common cause of this issue is the staining of the Reservoir that leads people to believe it is Full when it is in fact empty.
You can replace the Reservoir with a new one, or just check it regularly with the stick.

 

Perfect! Thank you for clearing that up for me! I know the coolant is leaking out rapidly now so I need to get the car on a flat surface to jack it up and get the trays off to find the source of the leak. I’ve never had a car that you fill from just a reservoir so I was quite perplexed by it!

 

Fingers crossed it's just a split hose or something like that.
While you are there check the condition of the Transmission cooler connections at the bottom of the radiator.
If those are at all rusted, then you need to replace the radiator ASAP as when they go coolant gets into the gearbox and destroys it.

 

Ta for the heads up, mate. I’ll definitely be checking that. I’ve had a nightmare with this and I’ve only had it 2 months. I had to replace the rear air susp solenoid and height sensors last month after the whole back end just lifted to max height! When it works though it’s the best car I’ve ever driven so I’m eager to get all these issues sorted.

Thanks for your advice!

 

what the ??! how are you supposed to fill a radiator if it has no cap? makes no sense , probably some dumb UK safety law. I hope i don't get arrested for complaining about it online

 

Thanks for providing picture I guess the pressure cap is on the expansion tank. As Boomer mentioned plug in top of radiator is a place to do pressure test which I would do and tell a lot. It could even be your pressure cap.

 

In the facelift UK models you fill the Reservoir which is part of the pressurised cooling system and has the Pressure release cap. The Japanese and EU versions are the same so not "some dumb UK safety law".
It looks like the pre-facelift models had a radiator cap as well as the Reservoir cap. Perhaps they just continued that in the USA on the facelift models?