Hello, we noticed a few slightly (ok, not really) interesting things on the weekend on my mk3 (mk2f) 1.3 SPI (AAV) and have a couple of questions...

Firstly it seems that the air filter is too thick and means the dustbin lid doesn't seal around the edges, causing no air to actually get drawn in through the piping as designed. It's a Halfords air filter - anyone had any problems? Either that or I'm missing a seal around the edge of the dustbin lid, should I have one?

Secondly is that it always seems to be drawing air from the exhaust manifold cover, ie warm air. Even with the air filter out (so it actually sucks from the piping) and fully up to temperature (cooling fan kicked in), there is no suction at all on the cold air feed pipe. I'm thinking at that kind of temperature it should have opened the flap to get some cooler air in? VAG-COM shows the intake air temperature at about 35 degrees with the engine fully hot - should the vacuum valve mounted in the dustbin lid have opened/closed by this temperature so the flap opens?

Any advice would be great! I know it's rather boring and probably no-one gives a shit but if it can be running a bit better then that's no bad thing!

Thanks,

Ray

Bump please!

Hello, we noticed a few slightly (ok, not really) interesting things on the weekend on my mk3 (mk2f) 1.3 SPI (AAV) and have a couple of questions...

Firstly it seems that the air filter is too thick and means the dustbin lid doesn't seal around the edges, causing no air to actually get drawn in through the piping as designed. It's a Halfords air filter - anyone had any problems? Either that or I'm missing a seal around the edge of the dustbin lid, should I have one?

Secondly is that it always seems to be drawing air from the exhaust manifold cover, ie warm air. Even with the air filter out (so it actually sucks from the piping) and fully up to temperature (cooling fan kicked in), there is no suction at all on the cold air feed pipe. I'm thinking at that kind of temperature it should have opened the flap to get some cooler air in? VAG-COM shows the intake air temperature at about 35 degrees with the engine fully hot - should the vacuum valve mounted in the dustbin lid have opened/closed by this temperature so the flap opens?

Any advice would be great! I know it's rather boring and probably no-one gives a shit but if it can be running a bit better then that's no bad thing!

Thanks,

Ray

With regards to the lid for the air filter, I can't recall seeing a seal in it. There may be a very primitive one in the lid where the lid sits on the housing, but I have a feeling that at most, it would be a small bead or smearing of rubber. Either way, i don't think it'd be essential for the housing to be totally air tight in this respect. The orange foam (or pink on OE ones) on the filter itself is always slightly too deep for the housing as it's supposed to compress when you clip the lid in place. If not, it wouldn't seal as well. This is often the problem, I find, with cheap aftermarket filters. This seal (foam) on the filter is either far too hard, or very madly made. Personally, I’d stick to Mann or Genuine ones.

At ambient temps above 17C, the flap in the temperature control unit (where the hot and cold air feeds meet) should be closed. -20 to +17 should be no more than 2/3s open. When the weather is hot, and the engine is up to temp, pull the temp control unit from the housing (leave the very small vacuumed tube attached though) and with the engine running, see if the flap inside is open or closed. Before hand, make sure the flap isn't stuck. It'll be stiff because it's spring loaded.

Thanks Daniel, some useful info there. I believe GSF do Mann filters so I'll treat myself to a new one soon.

By the flap being closed I guess you mean allowing the cold air to flow, which it never seems to do. I'll check it's not stuck tomorrow and visually check what's going on. Sounds like either the flap is stuck open or the vacuum valve in the dustbin lid is stuck open/closed, because there was absolutely no suction on the cold feed with a hot engine on a pretty warm day.

Thanks again for the info!

Well better late than never... I finally got round to it and bought a Mann filter and the ridge around the top/bottom is noticeably bigger on this new one, and I can now feel suction! The flap was letting the warm air in with the engine up to temperature (although with the assembly off, so the air being sucked in was probably ambient temp) So the flap isn't stuck and the vacuum is there, just whether the valve is letting it through at the right time. Will get another one if I see one in a scrapyard and try it out!

Thanks again