1.8 16v Heater only blows warm air :(

[Drucey 10]

Hi everybody, I have an issue with my car. It's started to only blow warm air when hot. I have recently started getting bits of foam coming through the vents the past few months. It's not long started. The engine has been flushed recently and has had new water pump and thermostat. I'm thinking the foam may be blocking something? or the heater matrix is clogged? Is there a way to check? Does anybody know if the heater matrix is easy to get to on the 1.8 16v.the car still runs fine gets up to temp. Just annoying with winter here. See a post on the net about the foam being the problem? But just don't know where to check. Any help or advice would be amazing. Thanks everybody.

[seanl82 23]

Possibly your bypass valves. Either they are working as they should and your matrix is blocked, or they've become stuffed up which is very common and just stuck to divert. The two pipes going to the matrix in the engine bay, there should be a bridge between them with a bypass valve each side. If you're confident your matrix will last, take them off and put some copper pipe directly to the matrix. The bypass valves are supposed to divert water flow if there is excess pressure in the matrix. Worth a try before replacing the matrix. Changing it is exactly the same across all types so you're in for a treat if that is the problem.

[Drucey 10]

Is it such a horrible job to change the matrix? :( thanks for the help.

[seanl82 23]

Not particularly difficult, just time consuming and there are a couple of nuts and clips that are sometimes difficult to remove.

Have a look in the wiki at the guide. Jim Bowen is having one of the problems right now!

[Drucey 10]

The valves are not very old as I have changed these not long back, I'm thinking it's possibly the foam causing the problems? It's been coming out the vents in bits.. :(

[seanl82 23]

Well you may as well change the matrix at the same time then. I may have read it wrong, when you say constant warm do you mean hot, or it won't go to cold when selected? If its that it won't go cold, then it will likely be the foam. If it doesn't get hot properly, it'll be nothing to do with it. You have to remove the heater box to change the matrix and sort the foam as the flaps for some unknown reason have big holes in, and are covered over by the foam. When it breaks down, the cool air doesn't divert so you get a constant hot stream.

[Drucey 10]

It blows cold fine, it just started to blow Luke warm when the car is at operating temperature. Was blowing nice and hot few weeks back. I change the coolant a lot and flush it through when I do.

[seanl82 23]

Does it warm up when sat in traffic, then cool down again when on the move? Worth checking as although you said you changed the stat, I had two brand new duff ones from ECP after another. Went and got a genuine one from VW and it was fine. Check it in a bowl of boiling water before fitting to make sure it opens as it should to save yourself a lot of hassle as I know what its like to change on the KR. Other than that, its the bypass valves or the matrix. Can't be anything else tbh.

[swiftkid 1]

The foam is from the flap in the heater box, nothing major to worry about. The heater flap in the control box has a sheet of foam across it and deteriorates with time or in my case when my heater matrix popped and soaked the foam. It won't be blocking anything, of anything it unblocking it!

 

You may have a blockage in your heater when you've changed the water, easy enough to do. Try bleeding the system, I'm betting that will help

[Drucey 10]

Yes, goes up when stood still and goes back down when moving. it's been fine since I got the car out the garage over a year ago. The foam has been coming through the vents for about 6 months or so and this has just started. It's not the foam jamming something round the back stoping it letting the hot air in properly? I'm not sure how it work? Haha.

[Drucey 10]

I did the coolant and flush in February it's been fine till now. Everything was work fine hot/cold over the last few weeks it's just the hot that I don't get very well now :(

[seanl82 23]

Yep, my money is on the thermostat then.

[Drucey 10]

That's also new did that with the pump in February. appreciate all the help people :)

[swiftkid 1]

It's a very simple system, fan in passenger footwell, through to a flap that is either open or closed. This is how it's not supposed to look but probably does now!

[Drucey 10]

That looks like the foam that's coming out, does it need the foam on it to work? What does the foam do? I have a feeling this isn't going to be easy to fix? Lol .

[swiftkid 1]

Well the flap is supposed to guide the air either through the heater matrix or straight out the fans. That flap, as I mentioned, moves and when the foam has gone it doesn't really do much. I had it all out when I did heater matrix and replaced the foam

[Drucey 10]

What foam is best to use and did you cover over the holes? Thanks for the help m8.

[seanl82 23]

I just used heat reflective tape when I did mine. It'll have nothing to do with your warm air problem though. I know you've replaced it, but the symptoms are classic thermostat failure.

[swiftkid 1]

It does sound thermostat related but you can tell if thermostat is stuck open if the car takes ages to heat up. I wouldn't assume that because you have changed something it hasn't broken, agree with Sean I'd be looking at thermostat

 

I just had some sticky back foam from hobbycraft I was using to stop rattles I just covered over the flap with, and yes those holes should be completely covered! But as said above, I'd start with thermostat, if I remember correctly its an absolute pain to get to that flap!

[Drucey 10]

Ok, I'll do that then m8, you seem to fix ine job and get another on these cars hahaha, I hope it's not the matrix. Have given it regular coolant changes and cleans.. Did you know the right way to replace the coolant (bleed it) so can change the thermostat and fill it up right :) big help m8!! Thank you so much.

[seanl82 23]

You can check if the stat is stuck open by checking the bottom rad hose as it's coming up to temp. The top one should get hot quite quickly, but the bottom one should remain cool until. Up to temp when the stat should open and allow hot water through to be cooled by the radiator. If it's stuck open, you're water will be being constantly cooled when on the move, and only warm the water up when sat in traffic when no air flow, which sounds like what you are experiencing.

[swiftkid 1]

Yea I know that feeling all too well!

 

I'm sure I'll be told I'm doing it wrong here but I tend to flush out the system whilst the thermostat is out then bolt everything back together, fill the radiator up through the top hose, undo the pipe on the header tank and raise it above the header so air can escape and brim the header then reattach everything and let the car run for a while with the header cap off.

[seanl82 23]

You can check if the stat is stuck open by checking the bottom rad hose as it's coming up to temp. The top one should get hot quite quickly, but the bottom one should remain cool until. Up to temp when the stat should open and allow hot water through to be cooled by the radiator. If it's stuck open, you're water will be being constantly cooled when on the move, and only warm the water up when sat in traffic when no air flow, which sounds like what you are experiencing.

[Dox 23]

If you suspect the matrix is blocked disconnect the pipes at the bulkhead and flush it through with a hose pipe in both directions

[Drucey 10]

Something Else I have just noticed if I select blower to the front screen it blows warm. But if I select it to blow in your face it blows cold. The car wasn't ip to temp as only drove a few miles down the road. Could that mean it's deffo the thermostat? Thanks