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Discussion Starter · #1 ·
---I shall add a serious of photos this coming weekend---

Following a recommendation in my project thread, I thought I'd share one of the more tricky jobs I've recently completed on my Golf - for reference, it is a Mk4, 2.8 V6 4Motion. Whilst there are obvious differences between mine and an R32, this may still be useful.

I would like to make you aware, I've tried to add suitable detail here and as such, I go on a bit like my wife when she has a catch up with the girls, however this thread does not discuss handbags.

Back on topic. I purchased my car with an engine management light on (constant, not flashing) with a printed scan reporting a failed Lambda sensor. The car ran relatively rough. I asked VW for a price for the part and then compared that with a Bosch item from EuroCarParts. Ordinarily, I'd avoid purchasing from somewhere like EuroCarParts, however Bosch have a high reputation in producing these sensors and £80 is vastly more appealing than £180.

I searched online for a guide on how to install the sensor and came upon this one on VWVortex. It wasn't quite what I wanted, so I decided to just crack on.

Jack x 2
Axle stand x 2
Halfords 22mm spanner
Conventional tool kit

There are 4 sensors on the car. The primary 2 sensors are situated in the exhaust manifold towards the rear of the engine bay. If you stand to the side of the engine bay next to the wing on the nearside (left hand side) of the vehicle and shine a light directly down, you will be able to make out the end of the sensors. A brand new one looks like this:

They have a distinctive ribbed black tube-looking section which comes out of the back of the sensor, carrying the wiring loom within. It is built to resist high temperatures found in the area. I would suggest you find a reasonably sturdy stool to place to the side of the car & place a towel and or some protective device over the wing of the car to prevent scratches as you may well lean over the area.

The Golf uses two manifolds which are referred to banks - hence the 2 sensors. Bank 1 Sensor 1 lives towards the offside (right-hand side) of the car, Bank 2 Sensor 1 lives towards the nearside (left-hand side).

Bank 2 Sensor 1, nearest the passenger wing is reasonably easy to access with the spanner because it is mounted in the exhaust manifold but points toward the heatshield mounted on the bulkhead - allowing you to get the 22mm spanner in place on the sensor. To unscrew the sensor, you turn the thread anti-clockwise. I found a lot of information on the internet about these sensors being fitted so tightly, only the Dwayne the Rock Johnson would be able to un-screw them without applying penetrating oils. I chose not to believe that and I'm pleased I made that decision.

For anyone like me who hasn't got great upper body strength, you can pull the spanner up in several repeat motions - bit like a fist pump. Obviously you only apply force in the anti-clockwise direction, but this pumping method helps free the bond between the exhaust pipe and the thread on the sensor which holds it in place over however many years it lived there. As soon as you can feel the spanner move, I found I only needed to turn the sensor about 90-180 degrees before I could remove the spanner and turn the sensor by hand. It's fiddly, but it's a damned site cheaper than paying Volkswagen to turn a bolt using a spanner at £50+ per hour (at least that's how I always looked at it) - it's the same bolt no matter who's turning it round.

For Bank 1 Sensor 2, nearest the driver side wing, the right-hand side of the car, there is both less access physically and less visibility. To add insult to injury, the sensor points slightly towards the centre of the car so getting accurate purchase on the existing centre requires a slightly different approach to the Bank 2 Sensor 1. The 22mm Halfords spanner is around 20cm long, so actually positioning it in place is half the trick. The method I found which worked best, was to place the spanner behind the Bank 2 manifold and onto the sensor. Whilst it gives you limited room to move the spanner, there's sufficient space to rotate it up and down by about 45-55mm - just enough to turn the sensor and free it of the locking bond between the thread and the manifold. This move is awkward - I mean by this point, there was builder's butt going on, tiredness, frustration, man-tears were on the horizon - that kind of awkward.

I tried simply pushing on the spanner - it went nowhere so I used the mini fist-pump motion to just apply a dab of pressure to the spanner. To my utter delight, it moved! I continued doing this as far as the spanner went down, then pulled the spanner off of the sensor, rotated the spanner 180 degrees, moved the base of the spanner (opposite end to the sensor) up through the 50mm of available space, slotted it on and did another fist pump. That's enough to free the sensor on the thread. You can then remove the spanner (gently, try hard not to drop it and if know you're gonna drop it, point it at the floor) and pull yourself and your body upright. In my case, I pulled my jeans up too.

Once the sensor(s) are free, the worst part is over. Go and get yourself a glass of water/coffee/bevvy.

Post beverage, you'll now want to prepare to pull through the wires from the sensors. In the engine bay on my car there was a small piece of heat-reflective material which was wrapped around the wiring from the sensors after the ribbed section (about 75mm from the metal component of the sensor). It's secured with three small poppers, the type you find on clothing. Un-pop them and lift out the heatshield. It'll probably look well-weathered if it's anything like mine.

Next section, lift the car to gain access underneath it. I'm not going to describe how to lift a car using jacks and axle stands as I'm sure there are suitable guides elsewhere. It's also incredibly dangerous and should only be done if someone has taught you how to do it and/or provided directions on how to safely raise the car. If in doubt or you haven't done it before, get a friend with experience to guide you and assist so you remain safe.

Key Rule - Don't get under a car unless you're 100% certain it is stable and safe to do so - period.

You are going to trace the cables from the sensor which run behind the heatshields at the back of the engine bay and down to the area where the catalytic converters are positioned. The heatshields are relatively light and thin and have a degree of flexibility to them, allowing you to push your hand up to guide wiring. I simply followed the existing wiring and it's positioning. You could, no doubt, choose a new route for it, but frankly, the standard route does the job quite ok, which is what I followed.

Trace the cable back within the confined spaces and make a mental note of which clips hold the cable in place are corroded - you might as well replace them another day as they will cost so little but keep the wiring firmly in the right location. A couple of mine fell to bits in my hand as I removed them.

Beneath the car on the driver's side (right-hand side) of the car is a black plastic cover - all of the plugs at the end of the sensors convene in this nicely protected junction-style box. two 10mm plastic screws hold it against the bodywork - they are probably designed for one use only and deform as they are screwed on (which reminds me I need to order a couple!) but I managed to re-use them. Trace the wire in question, unplug.

You are now going to pull the old sensor down through the channel the wiring went behind the heatshield. At this point, you have two options - secure the plug for the new sensor using something like electrical tape to the end of the old sensor and use the old wire to guide through the new one, or like I did, simply feed it all through by hand.

The rest of what's involved is obviously securing things back in place. I made a point of plugging in the plug from the new sensor (to the cars' wiring loom) into the junction box which allowed me to gauge how much slack I had on the wires and check if anything needed to be cable tied into a loop and secured. There's a small quantity of free space within the junction box which I used to hold some slack.

I have, historically, mounted the sensors into the exhaust pipe itself before negotiating the route for the wiring as I wanted the most strenuous part of the job (of installing the new sensor) complete first. Once the sensor was wound in, I used the exact same method of positioning the spanner as before, only difference being that once I got it tight, I only turned it until I felt that it wouldn't move - I really, REALLY strongly suggest you don't tighten it past that point. If you do and (hopefully this happens to nobody) but a part of the sensor falls off and runs down the exhaust pipe, you will need to pull off that part to take the debris out - not to mention buy a new sensor (which we'd all rather not do).

Once your cabling is correctly secured in the appropriate route/location, make sure you secure the heat-resistant fabric piece with the three poppers to the exposed wiring at the back of the engine bay - I'm referring to the section which isn't ribbed.

At this point, you can go back to the junction box beneath the car, screw back on the 2 x 10mm plastic mounting nuts, whilst hoping they don't crack like I did, check there are no loose cables, visually inspect the whole job, then the floor beneath the car, then check all of your tools are out by putting them back in their relevant cases/homes and you're ready to put the car on the ground.

Once the car is on the ground, you'll want to cancel the Engine Management Light which was on. When I first bought the car, I didn't have a tool to plug into the cars' OBD port, so I simply took the battery connection off for 60 seconds. I now have a tool (OBD Reader called a Scangauge) which I use to clear the code. Re-connect the battery if you used that method, get into the car and start it.

Let the car idle for 3-5 minutes and walk around inspecting the areas you've worked on to ensure cables aren't in contact with the exhaust, hanging down anywhere and that there are no unusual sights, scents or sounds. If anything seems odd or is unexpected, turn off the car immediately and investigate.

Once you're confident the car is operating normally, take the car for a gentle 10 minute drive, bringing it up to temp in a normal manner and once up to temperature, allow the car to rev right through the rev range in one gear.

Bring the car home, grab yourself another cup of coffee and pat yourself on the back. Hopefully, it won't take as long to do the job as it did to read my guide!

Hope this helps someone


· Registered
1,264 Posts
Nice job buddy!

Made me laugh when you said you go on a bit, but with alot of jobs the extra explanation is a big help, and a little confidence booster when you're
doing something yourself.

As far as im aware this guide is completely applicable to the r32, i may be wrong however.

If you ever look into modifying as apposed to 'reviving' have a word with florida747 (Dave) really sound guy, lives down your neck of the woods too! has the v6, and currently supercharging it.
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