VW MK5 Golf GTi TFSI Brake Booster Hose 1K0 612 041 GM Information

This is just a short post to help anyone else out and save them doing the research I had to.

The brake booster hose connects directly to the vacuum pump as part of the system to give power assisted braking. There is also a check valve which prevents boost from going into the vacuum pump.

Over time the hoses can become brittle and start to crack around the connections, the plastic check valve also becomes brittle and can be easily damaged when working on the car.

Failures of this part can result in several symptoms:

  • Loss of power braking assist
  • Check valve failing to close resulting in loss of boost pressure
  • Idle and vacuum issues

Side note: The short rubber hose between the check valve and the inlet is a popular place to take a boost tap from to operate a boost gauge or vacuum operated diverter valves such as the Forge Recirculating Valve (FMFSITVR ).

VW part numbers:
  • Original part number: 1K0 612 041 BM (shown below without extra vacuum nipple)
  • Superseded part number: 1K0 612 041 CH (also without extra vacuum nipple
1K0612041BM brake vacuum hose
1K0612041BM brake vacuum hose
  • Latest part number: 1K0 612 041 GM (as shown below with extra vacuum nipple)
If you car does not have a pipe for the vacuum nipple (e.g. AXX) then you can just block this off, the genuine part number for this is 056 129 777 which looks like a mini green traffic cone.
1K0 612 041 GM latest part number. Photo owned by ECSTuning.com

VW Mk5 Golf GTi (TFSI) Misfire When Engine Is Warm

This post summarised for anyone in a rush...

  • 2005 VW MK5 Golf GTI 2.0 (AXX engine)

  • Slight misfire on idle when engine is warm
  • No symptoms when engine is cold

  • New coil pack for cylinder 1

More information

I recently sold my 2005 Honda Civic Type R (EP3) and bought a 2005 VW Mk5 GTI in the hope of moving to something a little more torque-y and refined.

I was going through that first month or so of owning a new used car which I hate with a passion. You know, when you're constantly thinking:
  • Have I bought a lemon?
  • Was that a knock?
  • Is that sound normal?
  • Is the engine going to explode
Well anyway, during that enjoyable period I noticed that when the car was up to temperature it would slightly stumble occasionally on idle, most "non-car" people wouldn't have noticed it, but anyone into their motors would.

I did not experience any hesitation or loss of power, but after scaring myself with stories of compression loss and head gasket failure I decided the first sensible option would be to change the coil packs and spark plugs.

So I ordered the following parts:
  • Genuine VW coilpack - 07K 905 715 G (previous revision 07K905715F)
  • Bosch spark plug - 101 905 631 H (Bosch part number: FR5KPP332S)
Before I had a chance to fit these the misfire got much worse and finally conked out and wouldn't run at all.

Luckily I had an OBDII bluetooth adapter and Torque for Android which enabled me to read the OBDII fault codes to get a better idea of what was going on.

OBD Scan Result: 
  • P0300 - Random/Multiple Cylinder Misfire Detected
  • P0301 - Cylinder 1 Misfire Detected
  • P0302 - Cylinder 2 Misfire Detected
  • P0351 - Ignition Coil A Primary/Secondary Circuit
Coil A = Cylinder 1 so at least that seemed consistent. However, still not conclusive that this is a coil or spark plug issue.

I changed the spark plugs first but this made no difference. The old plugs and coils were pretty filthy though with lots of corrosion build up pretty much everywhere where you don't want corrosion build up.
bad bosch spark plugs from golf mk5 gti

After changing the coil pack on cylinder 1 the engine fired straight up and the misfire disappeared.

Problem solved.

Cleaning Cloudy/Foggy Car Headlights With Bar Keepers Friend

before and after cloudy headightsCloudy car headlights not only look bad, but they are also dangerous for two reasons:
  1. Reduces the amount of light which makes it out of the headlights and onto the road, where you want it.
  2. It impairs the all important scattering of the beam, causing glare for other road users.
It is possible to fail an MOT for cloudy headlights as it ruins the light scattering. A local garage tried to charge us £60 just to clean our cloudy headlights so it's well worth looking at alternative methods and doing it yourself!

There are many ways of cleaning headlights which have gone foggy and using Bar Keepers Friend is just one of them which I have used with good success so I thought I would share.

Bar Keepers Friend vs. Brite Powder Power

To avoid confusion from my photos, Bar Keepers Friend recently re-branded to Brite Powder Power, so they are exactly the same product, just a different label.

Bar Keepers Friend is a more familiar brand which has been around for quite a while and has many uses around the home including cleaning kitchen pans, toilets and as covered in one of our previous posts, it is also excellent at cleaning car windscreens.

How to clean your headlights

Cleaning cloudy car headlights with Bar Keepers Friend (Brite Powder Power) is very quick and easy and in a few minutes you will have lovely clear headlight lenses again.

The advantage of using this method to restore headlights instead of wet sanding them is that Bar Keepers Friend does not scuff up the lenses so much that you need to polish them back clear again.

For really badly cloudy headlights it may not be enough but for the price of Bar Keepers Friend on Amazon (£3.10 with Free Delivery) it's certainly worth a go.


  • Polishing pad or cloth
  • Bucket of water
  • Bar Keepers Friend

Step-by-step guide

Step 1. Lightly wash the headlights and surrounding area with the polishing cloth and water
This is just to remove any grit which might be sitting on the headlights. Even though the plastic used in headlights is generally very hard-wearing, you don't want to risk accidentally creating scratches in the lenses or paintwork around the headlights when you rub in the Bar Keepers Friend.

Step 2. Pour a small amount of the Bar Keepers Friend onto the damp polishing pad and work into the headlight lens. The moisture from the polishing pad will turn the powder into an abrasive paste and you should be able to feel that it is rough against the headlight lens.

You should apply a good amount of pressure and polish in a circular motion being very careful to avoid touching the paintwork as this could mark your paint.

Depending on how badly fogged your headlights are this could take up to 15 minutes of constant polishing for each headlight and you will need to re-apply the powder to the polishing cloth every couple of minutes. Who said saving money would be easy?

Step 3. Once you are satisfied that the headlights have been restored then you need to gently wash all the powder residue from around the headlights and bodywork. This is easily done with some water and sponge.

Step 4. Stand back and admire you restored car headlights.

Tried this out and impressed (or unimpressed) with the results? Please leave your comments below.

restored car headlights

Why does my car squeal?

If you are wondering why your car is making a squealing noise then this quick guide should help you find the cause of the squeal. Don't let it annoy you any longer...

99% of high pitched squealing noises from cars are likely to be caused by either:
  1. Fan belt
  2. Brakes
Identify the cause of the squeal
When the engine is cold and the car is parked, open the bonnet and then start the engine. The fan belt is often located on the left side of the engine and you should be able to see it moving when the engine is running.

Listen for noise coming from this area, particularly when the belt is under extra load.

You can put extra load on the fan belt in a few different ways depending on your particular model of car:
  • Increase the engine revs
  • Put the alternator under load e.g. turn on full beam headlights, heated rear windscreen etc.
  • Turn on the air conditioning
  • Turn the steering wheel to full lock and then back again
Cars most often squeal after the car has been left overnight, particularly if it is damp - this is because the alternator is putting extra load on the belt as it's trying to re-charge the battery and also dampness can reduce grip, causing the belt to slip.

If you can hear the squealing noise when the car is stationary, then the problem is probably your fan belt (also known as alternator belt, aux belt or accessory belt) and you should check out our guide on how to fix it.

A worn fan belt on a Honda Civic Type R
If you cannot hear the squeal noise when the car is parked with the engine running then it is quite likely that the noise is related to your brakes. Go for a drive with the windows down and determine if it happens when you are driving or only under braking.

Unless you have a seized brake caliper then any squealing is only going to occur when you apply the brakes to slow down. If you car squeals when you apply the brakes then I would strongly recommend taking it to a professional.