981 coolant cap issues

[Topbox]

Sorry if this has been mulled over before and I have missed it or failed to search adequately. I got a red message in the right hand instrument screen along the lines of "low coolant do not drive" which with ignition off, wait, on again turned to an amber warning, "coolant, monitor temperature while driving" So about 750 ml of coolant saw the float thing pop up, ignition on and computer says "yes" I'm good to go. Notice a bit of liquid under the car yesterday, assumed air con. Some coolant pooled under the cap when removed to top up. As I was in Charmouth at the time I rang @red rocket's go to independent Marque21 ( power of the forum) quick name drop and the car is on a ramp 90 minutes later. Result, no gushing coolant, just the odd bit of moisture in strategic locations. Prognosis coolant tank cap US (very hard to turn, does not click in place like oil cap, normal or wrong?) Quick call to Bristol OPC, new cap in the boot to fit tomorrow  Meanwhile after a top up in Bridport am now in Bangor, having enjoyed a rock steady 90c all the way. Thoughts gentlemen?? There is some web based stuff about the cap being hard to turn.

[andygo]

I had this on my previous 981.

If the cap is overtightened past a certain point, it breaks off the small tab thats designed to tell you the cap is tight enough. Bit of a daft approach IMHO.

 I'm confident if you look at your existing cap, you will see where the small tab has broken, and certainly if you compare new to old, it will become apparent.

Once I swapped my cap, no further loss of coolant and easy to turn.

Edited July 26, 2023 by andygo

[red rocket]

32 minutes ago, Topbox said:

As I was in Charmouth at the time I rang @red rocket's go to independent Marque21 ( power of the forum) quick name drop and the car is on a ramp 90 minutes later.

Glad a but of inside knowledge helped, Bob!

[iborguk]

40 minutes ago, Topbox said:

Sorry if this has been mulled over before and I have missed it or failed to search adequately. I got a red message in the right hand instrument screen along the lines of "low coolant do not drive" which with ignition off, wait, on again turned to an amber warning, "coolant, monitor temperature while driving" So about 750 ml of coolant saw the float thing pop up, ignition on and computer says "yes" I'm good to go. Notice a bit of liquid under the car yesterday, assumed air con. Some coolant pooled under the cap when removed to top up. As I was in Charmouth at the time I rang @red rocket's go to independent Marque21 ( power of the forum) quick name drop and the car is on a ramp 90 minutes later. Result, no gushing coolant, just the odd bit of moisture in strategic locations. Prognosis coolant tank cap US (very hard to turn, does not click in place like oil cap, normal or wrong?) Quick call to Bristol OPC, new cap in the boot to fit tomorrow  Meanwhile after a top up in Bridport am now in Bangor, having enjoyed a rock steady 90c all the way. Thoughts gentlemen?? There is some web based stuff about the cap being hard to turn.

Yup and had a similar issue re the cap being hard to turn "lock" on my 718 when newish to me, fixed with a new cap which had a revised part number.

Edited July 26, 2023 by iborguk

[iborguk]

Dried coolant on the threads is the theory re the cap being hard to turn and if the 981 has a similar revised cap as per the 718 I think the lug which engages the lock is bit bigger as people were snapping those as well.

Edited July 26, 2023 by iborguk

[Topbox]

40 minutes ago, red rocket said:

Glad a but of inside knowledge helped, Bob!

Sure did Peter, hope your having a great trip to Norway 

[Topbox]

Yep the guys at Marque21 thought a lug inside the cap had snapped off ,,,👍

[cozzykim]

If this was me, after my recent engine  event, I'd also be replacing the engine bay cap.

Mine was also not sealing properly, so propbably leaking coolant when pressurised.

In fact it wasn't pressurising properly, allowing the coolant to boil, leak from the cap and then pull in air as it cooled down. This resulted in a sudden 120 degree indication and a "stop engine" message.

When I took the engine cover off (what a faffing nightmare that is) I could hear the cap hissing.

I managed to tighten it temporarily enough to run the car, but had both caps replaced at my interim service a few weeks later, as the boot cap was also as described above, tab broken and not sealing properly with dried coolant in the threads.

[Topbox]

@cozzykim ok where is the engine bay cap and what does it do exactly, never heard of this but clearly, interesting, 👍 Despite not tightening to hard in Bridport, I can not undo the water cap in the boot by hand, and I don't have a suitable wrench with me as I'm on the road. Seems to be ok though touch wood 🪵

Edited July 28, 2023 by Topbox

[cozzykim]

26 minutes ago, Topbox said:

@cozzykim ok where is the engine bay cap and what does it do exactly, never heard of this but clearly, interesting, 👍 Despite not tightening to hard in Bridport, I can not undo the water cap in the boot by hand, and I don't have a suitable wrench with me as I'm on the road. Seems to be ok though touch wood 🪵

There's another coolant cap under the engine cover. You have to put the hood in service position, remove all the insulation above the engine cover, and then remove the engine cover to get at the coolant header tank.

The clearance to get at the cover bolts is very tight (I took the firewall carpet behind the seats out to get to some of them, though the indie who replaced the caps somehow got his hands in to remove the front bolts without doing this), the thick carpet/foam over the engine cover is a bugger to remove first, and the engine cover itself is a very tight fit between the boot lip and back edge of the hood, so not for the faint hearted. I managed to put a tiny scratch on my boot lid even though I had a towel on it, as the engine cover has extremely sharp edges which penetrated the towel.
As soon as I opened the engine cover I could hear the inner cap hissing. A quick clockwise turn stopped the hissing, but I then took it off to look at how it seals, and to run the engine with the system open to check for air locks.
Mine had obviously been allowing the water to escape, then boil as it wasn't properly pressurised, so losing coolant, then allowing air back into the system as it cooled down.

Sorry if I'm repeating myself as I've outlined this before, but it was an eye openerfor me, and could have resulted in a blown gasket etc.

Both new caps turned and clicked easily, where the original caps were very hard to open/close, and had threads covered in coolant salty deposits.
In one thread I asked about lost coolant, now I know why, and my car hasn't lost any since the caps were replaced.

[Topbox]

@cozzykim thanks for the comprehensive reply, good to know, much appreciated. I'm on a little touring holiday around bits of England I have never or just briefly visited. Off to the Lincolnshire wolds tomorrow, some pleasant roads there I'm told. Then onto Cardigan in South Wales.

[Ninja02]

Bob,

Had a similar problem with the coolant cap hard to turn.  New cap bought and fitted, new cap is easy to turn (was a few years ago now though)

Phill

[Green Genie]

Hmmm interesting post, my coolant cap has always been difficult to fully tighten (the one in the boot) even with some lube added to the threads. Been like this since I bought the car at 3yrs old and 7.5 miles. Not loosing any coolant at the moment, I’ll get a new cap next time I’m near my OPC. Presume they’re not too expensive even with the Porsche tax?

[andygo]

About a tenner I think and a very nice shade of blue..

Edited August 5, 2023 by andygo

[Topbox]

1 hour ago, Green Genie said:

Hmmm interesting post, my coolant cap has always been difficult to fully tighten (the one in the boot) even with some lube added to the threads. Been like this since I bought the car at 3yrs old and 7.5 miles. Not loosing any coolant at the moment, I’ll get a new cap next time I’m near my OPC. Presume they’re not too expensive even with the Porsche tax?

My new cap spins on and off easily. When you tighten the cap it should click and then stop turning, the oil filler cap is the same, so maybe try that to get a feel for the action.  In fact the cap is black but has a small blue symbol on the top, er, in a very nice shade of blue. I paid £21 plus VAT from OPC Bristol, expensive enough for a bit of moulded plastic. I expect an OPC would post a cap out to you.