Pattern Part Header Tank Problems.

Morning all, I had a replacement header tank fitted recently , it came from a respected Porsche parts supplier (no names!) so I assumed the pattern part would work fine. Not so it seems... I lost about a litre of coolant thru the filler yesterday and the cap will not tighten properly when the coolant is warm. It feels like the threads have gone on the header tank neck. Has anyone else had a similar experience?

Just a quick update on this, I've tried a couple of times (coolant hot and cool) to tighten the cap to the coolant tank neck. It's only tightening so far and then it runs to loose again! .. as if the threads are broken. both tank and cap are new (cap is a .04 ) Reading up on it, apparently it can be quite difficult to seal new caps, and rennlist suggests using silicone spray on the threads, this hasn't helped. The car is unusable as the coolant is boiling over as soon as it reaches temperature. Has no one else come across this?

well yes an no .. the plastic thread if damaged will cause this but so it will if its the cap .. The only thing i can suggest .. turn the cap on the bottle as if you were undoing it .. when it " clicks " and you feel it drop then do it up . i doubt this will work but it will line up the threads spot on . other than this ill have to assume one of the threads is damaged . You already know not to drive it untill its fixed .. it will dump coolant . Awww just a thought .. have a good look at the rubber seal inside the coolant cap .. i had one a few weeks ago were it didnt sit flat .. it was kinda caught on the threads , gave it a curved look .. a screwdriver to push it in place and it worked .

Thanks DM I'll have another look at the seal on the cap but I'm pretty sure it's seated properly. Other than that it's back to buying another header tank and cap :roll: A quick question on this, would over pressure from the engine (start of a head leak) cause the cap to break thru the threads? I'm not trying to be a doom sayer but thought I'd mention! I would assume that the relief valve would open before this would happen anyway.. assuming the relief valve is functioning properly!

Erm .. no . You want a quick check ? leave the coolant cap off and start the engine .. if you get the coolant pour out of the coolant tank within seconds then you have a headgasket fault . it will normally take a good few mins for the lvl to raise a bit .. When we fill these with coolant we get someone to rev them at 3K rpm .. we then top up coolant and fit the cap beforedropping the revs .. If a head gasket had failed then we would have water in our faces ! Basically a headgasket fault is very rare .. and unfortunatly it normally ends with D chunk as water has got into the cylinder and hydrauliced the engine .. broken linner basically . Im in the .. its not headgasket camp atm .

Brilliant! Thanks a mil for that DM.

Bit of a bodge which I wouldn't do personally, but you could try some ptfe tape around the threads of the bottle. It might build the threads up enough to stop the cap threads popping over them when tightened. Even if it worked though would you be happy setting off on a big trip like that? It's a bummer mind. I've been considering one of those bottles. £160 vs £350 from Porsche. It's the only component in my cooling system that I haven't renewed. I think the only 'proper" fix is buy a new bottle, or speak to the supplier, but they're bound to say you've done it.

Thanks Marky , I'm a bit p1ssed off that I bothered with the spurious part and should have gone OEM and saved myself a lot of hassle and extra labour :roll: Oh well, I'll prob need to get a new cap again too. If the old one is damaged it'll screw up the new header tank. Literally. By the way , it's more like £400 for the Porsche item, unless you've found cheaper?

Morning Ballcock, £350 was just the price last time I enquired at Porsche but that was a while ago. Obviously you'll get 10% off by asking your parts guy, unless he's an ogre. :wink:

Try a new cap first? Or the old one?

Morning guys, getting a loan of a cap to try first, Thanks Griffter. Looks like they're more like £450 at this stage. Plus vat and postage :roll: https://www.design911.co.uk/mobile/#part;id=6214 May give local OPC a shout but judging by past performance I could be waiting weeks :what:

I bought a pattern part Expansion tank from Car Parts 4 Less for my 3.4 C2 last year. No particular issues fitting it (with a degree of patience), and it worked a treat https://www.carparts4less.co.uk/search/205330081 Around £85 delivered, depending on the current discount code. Cheers

Thanks for the info Geoffers.

I recently had one fitted to my 996T, not sure if it's the same but the deroures site ( https://www.deroure.com/partinfo.as...31&SMA=0&SMO=0&ST=99633121900&SC=1&PBID=75482 ) suggests the same part number 99610615704 is valid for later C2's. They list it at £86 plus vat plus delivery etc but it will be genuine Porsche.

Did you check the rubber seal in the cap at all ? Its only i had something very similar with a brand new cap a few weeks back .. the seal had caught in the threads and wasnt sitting flat .