Swirlpot Cap - probably an obvious question....
Discussion
The blue cap on the swirlpot is not a pressure cap. It can't be as the rubber seal a) has a hole in it in the middle, b) isn't flush with the top of the cap and c) there are 'vents' around the edge...
Is this normal? I should have expected that the system would be pressurised.
I ask because I have a cooling issue which is made worse by the fact that the cap allows the system to vent steam into the engine bay.
Is this normal? I should have expected that the system would be pressurised.
I ask because I have a cooling issue which is made worse by the fact that the cap allows the system to vent steam into the engine bay.
Hi Greg,
I guess you're talking about the coolant expansion tank between the fans and main exhaust cat. The swirlpot is the one next to the engine with a brass screw on top. The system should be pressurised, so it's possible that the blue cap is knackered. I think it's a VW part and should be easy to replace. The expansion tank should be kept approximately half full. If you're filling it up completely I guess this might cause steam venting?!
I guess you're talking about the coolant expansion tank between the fans and main exhaust cat. The swirlpot is the one next to the engine with a brass screw on top. The system should be pressurised, so it's possible that the blue cap is knackered. I think it's a VW part and should be easy to replace. The expansion tank should be kept approximately half full. If you're filling it up completely I guess this might cause steam venting?!
Greg M said:
I don't have an expansion tank in my pre cat... Just the aluminium tank with the blue VW cap.
That is your expansion tank, you don't have a swirlpot as such the two are combined. If you think it's an issue just replace the cap it's a period Golf one.
Edited by V8 GRF on Tuesday 21st May 07:53
The standard fittment is a Mk1/2 VW Golf and Early Audi cap. They are not directly vented and are for pressurised systems. My Griff is a Pre-cat and uses the standard VW blue cap. Have recently changed it, they are only about £5 for original German made items. If the coolant keeps venting out the cap, and the cap is reletively new, then the issues lie elsewhere. Have you got any airlocks? Is the system overheating? All questions to ask. Hopethis has been helpful. Regards, Pete
Here's the cap I've got. You can see that there's no pressure valve and that the rubber seal doesn't sit flush with the top of the cap. This allows the cap to vent on the 4 channels at the sides.
It sounds to me that I need to get a cap with a pressure relief valve as a starting point. Then move on and see what's next...
The car is really just finding it's boundaries at the moment. Or more accurately the boundaries of my wallet....
It sounds to me that I need to get a cap with a pressure relief valve as a starting point. Then move on and see what's next...
The car is really just finding it's boundaries at the moment. Or more accurately the boundaries of my wallet....
Greg M said:
Here's the cap I've got. You can see that there's no pressure valve and that the rubber seal doesn't sit flush with the top of the cap. This allows the cap to vent on the 4 channels at the sides.
It sounds to me that I need to get a cap with a pressure relief valve as a starting point. Then move on and see what's next...
The car is really just finding it's boundaries at the moment. Or more accurately the boundaries of my wallet....
Hi Greg, that cap is not right, there should be a piece in the middle. Get another cap! eBay do them - http://www.ebay.co.uk/itm/VW-GOLF-MK1-MK2-1-6-1-8-...It sounds to me that I need to get a cap with a pressure relief valve as a starting point. Then move on and see what's next...
The car is really just finding it's boundaries at the moment. Or more accurately the boundaries of my wallet....
There should be a pressure release mechanism, that cap will just vent the coolant when hot. Get rid of it mate. All the best, Pete
the pic you have posted up has its middle missing/gutted as said already 
no doubt you're missing that important bit. Question is where is it? For peace of mind have a look into your expansion tank just to make sure it's not floating somewhere or blocking the exit tube which is quite large. And don't be tempted to buy any cheap aftermarket cap. I once did. Cap looks similar but without the Volkswagen logo. Inside is different as well. Fitted it, was leaking soon. Had a look and realized the pressure valve came loose and was literally hold in place by just a tiny spring which came off while touching it. Just imagine this bit would have already started its journey through the engine.
OK, update....
The cap I have (just) replaced is one I bought shortly after buying the car as I lost the original.
The new one I have bought, which allows the cooling system to pressurise, has made an enormous difference to my coolant loss; from from 2+litres/10miles to <.5litres/10miiles. Ok, not perfect but significantly improved.
Thanks to PeteGriff for going all-out to confirm what I thought. It may seem like a small thing but it gave me the confidence to say 'this isn't the right part' .
Anyway, next step is to identify the significance of the losses from the radiator hoses; then it's the radiator itself.
G
The cap I have (just) replaced is one I bought shortly after buying the car as I lost the original.
The new one I have bought, which allows the cooling system to pressurise, has made an enormous difference to my coolant loss; from from 2+litres/10miles to <.5litres/10miiles. Ok, not perfect but significantly improved.
Thanks to PeteGriff for going all-out to confirm what I thought. It may seem like a small thing but it gave me the confidence to say 'this isn't the right part' .
Anyway, next step is to identify the significance of the losses from the radiator hoses; then it's the radiator itself.
G
Hi Greg
If you are filling the expansion tank up to the top then you WILL loose about half a litre. Chims and Griffs all do this and have their own level in the expansion tank. Mine is about 2-3 inches from the bottom. After I fill it, it finds its own level and then I do not loose any more from one month to the next.
If you are filling the expansion tank up to the top then you WILL loose about half a litre. Chims and Griffs all do this and have their own level in the expansion tank. Mine is about 2-3 inches from the bottom. After I fill it, it finds its own level and then I do not loose any more from one month to the next.
WOO5IE said:
Hi Greg
If you are filling the expansion tank up to the top then you WILL loose about half a litre. Chims and Griffs all do this and have their own level in the expansion tank. Mine is about 2-3 inches from the bottom. After I fill it, it finds its own level and then I do not loose any more from one month to the next.
I'd agree, but I'm not sure where the level is on a pre-serpentine as they have a different system to a serpentine with an expansion chamber and a swirlpot. If you are filling the expansion tank up to the top then you WILL loose about half a litre. Chims and Griffs all do this and have their own level in the expansion tank. Mine is about 2-3 inches from the bottom. After I fill it, it finds its own level and then I do not loose any more from one month to the next.
That said if your car dumps coolant and doesn't overheat and the level stays consistent then don't keep filling it as that will be the system's 'level'. If you keep putting more water in over this point the system will continue to dump the excess coolant so you're not actually losing required coolant just excess.
I'd suggest you drive the car with some spare coolant mix in the boot as an emergency in case you do have an issue but try to resist topping-up now you have a working pressure cap.
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