LEAKING METAL COOLANT PIPE

LEAKING METAL COOLANT PIPE

My 2007 VW Polo 2.0L Highline has just turned eight and it seems like she is going to start giving me  problems. Just yesterday, on my way back from Paarl, after driving a total round trip distance of approximately 300 Km, I was jolted to attention by the pong-pong sound of the dashboard alarm/buzzer. Looking at my VW Polo's instrument panel, saw the red thermometer symbol flashing on the cluster display  and the heat gauge was hovering around 100 degrees. The needle was lying just beneath the first red line in the gauge and I felt my heart throbbing in my throat. I immediately thought  the worst, that my cylinder head gasket may have popped, but lucky for me I was just a few hundred meters away from home and not on a deserted on an open road somewhere in the outback. Never in all the time I owned my VW Polo 2.0L Highline has anything like this ever happened. She currently has 105 ??? Km on her clock and is due to go for a major service soon, especially for the cam belt replacement. Considering I'm only averaging about 13 000 Km per annum, she has been put to very little use.

Anyway, because the instrument panel display symbol was flashing red, I kinda thought it was the oil light. I muttered to myself, that it can't be that the oil is low, because I checked it before the trip and even topped it up. Then I realized that the oil symbol is an oil-can, but that water is symbolized by a thermometer.  However  I drove my VW Polo 2.0L Highline into my driveway, switched off the engine and when I popped the bonnet I could hear hissing caused by the steam that was escaping. Yet, I couldn't see where it was steaming  from, though I saw a steady stream of green coolant running past my shoes.  I instinctively pulled out the dipstick and saw that  the oil level was normal and even more importantly that the oil was translucent and didn't look like dirty yoghurt, like when water gets into the oil. I then removed the PVC engine cover and saw a thin stream of green coolant squirting from the rubber hose that connects to the expansion tank at the point where it connects to a metal coolant pipe and held together with a spring loaded clamp. The thin stream of coolant didn't justify the amount of water streaming on the ground. I  thought it was a welsh plug that got pushed out by the water pressure, but it wasn't. After taking a closer look,  I saw coolant leaking from the junction where  the metal coolant pipe fits into a round hole in the engine block which is situated at the back end of the alternator, like right next to the metal housing that contains the thermostat,  with the rest of the pipe hiding behind the distributor pack and situated below the knock sensors.

Suddenly this all looked very familiar to me. I've had a similar problem with my 1999 Renault Megan Scenic a few years back. The leaking metal coolant pipe in question had two rubber O-rings in tandem around it, on the section that gets inserted into the round hole in the engine block. The rubber O-rings are the only two thing that prevents water from escaping. At the time I thought is was quite lame of Renault to design such a flimsy setup, instead of pressing a pipe stem into the engine block, to which a rubber hose could be clamped. Anyway, be that as it may, Volkswagen used the very same exact old concept used by Renault on their 1999 vehicle on a 2007 VW Polo, but with only one rubber O-ring.  I think it really sucks when some design feature that is commonly known to be troublesome is perpetuated in later models as impetus to a cash cow business model. VW must be selling millions of these metal coolant pipes per annum which is horrendously expensive considering that its just a cheap piece of mild steel  pipe. No rocket scientist was needed to design it, bend it, or spray it black. In fact a copper pipe equal in length costs less than one third of its price.

Be that as it may. The metal coolant pipe that protrudes from the engine block is in fact the only metal pipe in the entire cooling system and is made of such a thin metal that it will corrode to nothingness within a few years or less.  Besides the single rubber O-ring perishes from the engine heat and the cause of water and coolant leaks.  It is the weakest point of  failure in VW, Audi, Skoda and Seat vehicles, however  the trick is to keep the coolant to water ration at 50/50 or 1:1 since the coolant stems corrosion. But if for whatever reason the coolant ratio has a lot more water than coolant, then that metal coolant pipe just isn't going to last.  After going through the trouble of removing this pipe, I was tempted to make-up this pipe from copper pipe and copper fittings but since it is going to make contact with the engine block, corrosion of different metals in the presence of water is far worse than the corrosion between two metals of the same kind. 

The problem I had with my metal coolant pipe installation was that after I removed it, I discovered that it wasn't the correct part. The part number is 06A 121 065 E but there are like dozens of variations amongst which are the 06A121065 AR, or the 06A121065 BK, or the 06A121065AP, or 06A 121 065 N, or the 06A121065D that is used in the Audi A3 1.6, the Skoda Octavia 1.6, the VW Golf Mk IV 1.6, the VW Jetta IV 1.6, Seat Toledo  Mk II 1.6,   Seat Leon 1.6, Seat Ibiza Mk III 1.6, and  the 06A121065 Q and 06A121065 BD used in Audi TT's and other Audis.  Metal coolant pipe 03G121065H / 03L121065AJ / 03L 121 065 AJ are use in VW, Audi, Seat's and Skoda's, 06K121065L and 5Q0122291H used in VW Golf VII, 04L 121 065AJ  - 04L121065AJ is used in Audi A3, VW Golf 2.0 & + 1.6 L Diesel, 06B121065L is used in VW Passat, 06H121065 D are used in the Audi Q5 2.0 TFSI, Audi A4, B8, A5 and 8T.  06C121085F is used in the Audi A6 and A4 V6 3.0L Convertible. And the list goes no...

By looking at the picture of the two metal coolant pipes below, the difference between them are clearly visible even though they look alike. I could theoretically use this pipe, but the mounting bracket was in a different position, which meant I couldn't secure it properly, and I wasn't going to take a chance to fit it. The fact that the end of the pipe was a little longer and curved upwards were minor and totally surmountable. But it's best to get the identical replacement, so quote your cars VIN when buying it. Replacing this pipe is roughly a three hour job and its difficulty level is about a four and totally doable by the average hands-on DIY VW, Audi, Seat or Skoda owner.  Tools needed, are a grip pliers or water pump pliers to slacken off the water hose clamps, a 6 mm hex key to remove the distribution pack and bracket, a 7 mm hex key to remove the bolt marked as 10 on the cooling system diagram, a 14 mm socket and ratchet to remove the knock sensor bolts and a 4 mm torx to loosen the air filter. That's it.

It is only a matter of time before every VW, Audi, Seat and Skoda's cooling systems that sports this metal coolant pipe develops a leak. In my case the pipe was perforated beneath the rubber hoses with small holes that a nib of a pen could go through. In fact by just scratching the rust from inside the pipe with screw driver only made the holes bigger. It is inevitable that this metal coolant pipe is going to disintegrate through  rust because it is made of a far less durable metal than the engine block metal, besides the rubber hoses are bound to outlast this metal coolant pipe.  It would be worth your while to buy one of these metal coolant pipes and keep it in storage, because it is inevitable that this pipe is going turn to rust. When I went to the agents they had no stock and they could get one of two that were in stock at the factory within two days. This tells me this pipe is so popular that the agents get  sold out very quickly. In fact they only guaranteed this metal coolant pipe  for  24 months or  39 000 km or 24,000 miles. Yeah,  know that sucks... hard.

A word of warning though. Keep a magnet close-by when replacing this pipe because I dropped the allen key head bolt marked 10 on the cooling diagram somewhere below. I spent almost half and hour looking for this bolt but finally found it underneath the  clutch cable bracket on top of the gearbox. The screw rolled into a little crevice beneath the bracket and it cannot be seen from above.  This green coloured 7 mm  hex key headed bolt slipped from my hand while trying to screw it into position which is somewhat awkward  to get into position because of the clutch cable bracket obstruction. I searched beneath the car on the ground, between the front suspension mechanisms, stuck my fingers between the drive shaft and the engine, and all along the control arms and finally found it by using a magnet. Another thing that sucks, is that the long screw of the distributor pack bracket is made of some kind of  soft metal. I damaged its allen key head when I loosened it by hand, fortunately a 10 mm spanner also fits. The other two shorter screws are of a much harder metal. The images below gives you a fair idea of what it entails to replace this ye metal coolant pipe.  Remember when reassembling to re torque the Knock sensors and take care that the connector for knock sensor for cylinder 3 & 4 is turned away from the distributor pack bracket before tightening.

Water/coolant  leaks from the O-ring seal where it enters the engine block.

The coolant pipe runs along two sides of the engine block, 
right below the knock sensors.

The distributor pack unplugged. Be careful not to
break its clip when disconnecting

The distributor pack and plug wires clearly marked
with the first four letters of the alphabet

The distributor pack moved out of the way, sort of flipped-up.

As can be seen the long screw is different from the shorter black screws,
take care not to break of off on the engine block

The distruibutor pack bracket that straddles the coolant pipe. 

The Knock sensor for cylinders 3 & 4 removed after the distributor
pack was removed and positioned out of the way.

At the  90 degree bend of the coolant pipe with the knock sensor above it.

The coolant pipe is clearly visible and so is the rust that
poured out from the engine block.

The air filter must be removed to get the the mounting screw and the
rubber hoses at the end of the metal coolant pipe.

Removing the clamps that holds the rubber hose onto the metal coolant pipe.

The metal coolant pipe with the two rubber hoses disconnected.

This is the space where the metal coolant pipe resides. The two screw holes
for the knock sensors are clearly visible.

The cooling system of the VW Polo Classic. The metal pipe is coloured red.

The part number  06A121065 E is stamped on the wing that
aligns the distributor bracket.

The pipes are similar but the new one is slightly longer and curved upwards
at its end, yet have the same part number. The O-ring is   3mm x 20 mm

As can be seen, the mounting brackets on the two pipes doesn't correspond