FSI Up To Old Tricks, + Lesson Learned

Exe_Chris

Member
In what will probably not be a surprise to many on here, my FSI had to go the last couple of miles home last night on the back of a recovery truck due to a cooling system failure. Where the story differs a bit is that I'd just (earlier in the week) had the death pipe, thermostat housing, expansion tank, and the vent pipe from the tank, all replaced. What was not replaced, however, was the other infamous part of the system, the y pipe. The photo below shows the result. The y piece failed, causing coolant to spray all around the engine bay. From first smelling the tell-tale aroma to stopping was probably 15 - 20 seconds. Fortunately it's a small hose so coolant isn't dumped instantly, but the warning light came on soon enough. The car was at least considerate enough to break down right by a layby!
What I think happened was that the pipe was on its last legs already - the small plastic end part has just totally crumbled apart in the coolant hose - and the repairs to the other parts of the system have exposed the y piece as the remaining weak point. Once the main system was up to proper pressure, this has just given up the ghost. I'm in the process of ordering a replacement for the y piece, as well as the hose it connects to and the relevant spring clamps (both probably over-cautious), and a couple of bottles of G13.
Fortunately it's easy to replace, so once I have the bits it should be back up and running pretty quickly. The lesson here is: DO NOT REPLACE THE DEATH PIPE AND THERMOSTAT HOUSING (COOLANT REGULATOR HOUSING) WITHOUT ALSO REPLACING THE Y PIECE (OFFICIALLY 1J0 121 087 D COOLANT FLANGE).

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Thanks @Exe_Chris - just about to get the coolant pipes (DEATH PIPE) and THERMOSTAT HOUSING (COOLANT REGULATOR HOUSING) replaced on my 1.6 FSI (I'm now running the ProBoost ECU), so wonder if you know the part numbers of those other two parts you mention?
 
the smaller y pieces near the expansion tank also get brittle, i replaced those with brass y pieces when i had an fsi. when i removed the old plastic y pieces they were indeeed very brittle. i'd replace those too if you haven't already. cheers
 
In what will probably not be a surprise to many on here, my FSI had to go the last couple of miles home last night on the back of a recovery truck due to a cooling system failure. Where the story differs a bit is that I'd just (earlier in the week) had the death pipe, thermostat housing, expansion tank, and the vent pipe from the tank, all replaced. What was not replaced, however, was the other infamous part of the system, the y pipe. The photo below shows the result. The y piece failed, causing coolant to spray all around the engine bay. From first smelling the tell-tale aroma to stopping was probably 15 - 20 seconds. Fortunately it's a small hose so coolant isn't dumped instantly, but the warning light came on soon enough. The car was at least considerate enough to break down right by a layby!
What I think happened was that the pipe was on its last legs already - the small plastic end part has just totally crumbled apart in the coolant hose - and the repairs to the other parts of the system have exposed the y piece as the remaining weak point. Once the main system was up to proper pressure, this has just given up the ghost. I'm in the process of ordering a replacement for the y piece, as well as the hose it connects to and the relevant spring clamps (both probably over-cautious), and a couple of bottles of G13.
Fortunately it's easy to replace, so once I have the bits it should be back up and running pretty quickly. The lesson here is: DO NOT REPLACE THE DEATH PIPE AND THERMOSTAT HOUSING (COOLANT REGULATOR HOUSING) WITHOUT ALSO REPLACING THE Y PIECE (OFFICIALLY 1J0 121 087 D COOLANT FLANGE).

View attachment 77844

Without a doubt the cooling system conduits are great weak points of the FSI, not up to the 110°C running temperature of the FSI, especially parts with the small pipe, there are a few of them. I am coming more and more to the conclusion that FSI members should group together and organise a group buy of more sustainable parts made of silicon/metal. As a step in this direction if you buy a new replacement could you be so good as to measure and post its accurate dimensions. After bit of digging this perked my interest ...


Andy
 
Thanks @Exe_Chris - just about to get the coolant pipes (DEATH PIPE) and THERMOSTAT HOUSING (COOLANT REGULATOR HOUSING) replaced on my 1.6 FSI (I'm now running the ProBoost ECU), so wonder if you know the part numbers of those other two parts you mention?
Hi,

All the part numbers you want will be identiable here


If time later I will return with a pointer towards a good source for the thermostat housing.

Andy
 
Without a doubt the cooling system conduits are great weak points of the FSI, not up to the 110°C running temperature of the FSI, especially parts with the small pipe, there are a few of them. I am coming more and more to the conclusion that FSI members should group together and organise a group buy of more sustainable parts made of silicon/metal. As a step in this direction if you buy a new replacement could you be so good as to measure and post its accurate dimensions. After bit of digging this perked my interest ...


Andy
@Andrew
Re a more robust version of the "Death Pipe" etc, since stainless is hard to work with, would copper be suitable? Easier to work, fabricate and join (solder, silver solder, or braze), with many fittings available both domestically (DHW/CH) and in the industrial/marine markets.
Mac.
PS: If anyone has a dead Death Pipe available, I'll take it on as a project.
Mac.
 
Thanks @nod
@Andrew
Re a more robust version of the "Death Pipe" etc, since stainless is hard to work with, would copper be suitable? Easier to work, fabricate and join (solder, silver solder, or braze), with many fittings available both domestically (DHW/CH) and in the industrial/marine markets.
Mac.
PS: If anyone has a dead Death Pipe available, I'll take it on as a project.
Mac.

I hope to have a dead one next week, so if no one has sent you one by the end of next week, remind me.
 
@Andrew
Re a more robust version of the "Death Pipe" etc, since stainless is hard to work with, would copper be suitable? Easier to work, fabricate and join (solder, silver solder, or braze), with many fittings available both domestically (DHW/CH) and in the industrial/marine markets.
Mac.
PS: If anyone has a dead Death Pipe available, I'll take it on as a project.
Mac.
My first steps would be to review the design with a mind to simplification of fabrication. I remember looking into the history of the part and from memory it dates back from 1996 in some VW models. My point is I suspect some design elements relate to these earlier models and are redundant for the FSI, for example the two lugs, look like locating lugs to me and I don't think used in the FSI. The big fabrication headache is the flat side presumably to overcome some space restriction in some applications, near impossible to DIY but is it needed with our FSIs? - I think not but needs carefully checking. Cable clip? Is it used on the FSI, not on one of mine! (Maybe some previous mechanic got it wrong and could not be bothered to start again), it is used on the A2 1.4 petrol (same pipe)! Does it have to have the sharp kink?

While not wanting to dampen you enthusiasm other design elements like the rolled lips and grove for the C clip need specialised tools to my mind, all a bit beyond the DIY in metal. As the ends locate into fixed items (coolant pump and thermostat housing I would have though the overall length would need to be accurate to well under 1mm!

Good luck.

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Andy
 
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My first steps would be to review the design with a mind to simplification of fabrication. I remember looking into the history of the part and from memory it dates back from 1996 in some VW models. My point is I suspect some design elements relate to these earlier models and are redundant for the FSI, for example the two lugs, look like locating lugs to me and I don't think used in the FSI. The big fabrication headache is the flat side presumably to overcome some space restriction in some applications, near impossible to DIY but is it needed with our FSIs? - I think not but needs carefully checking. Cable clip? Is it used on the FSI, not on one of mine! (Maybe some previous mechanic got it wrong and could not be bothered to start again), it is used on the A2 1.4 petrol (same pipe)! Does it have to have the sharp kink?

While not wanting to dampen you enthusiasm other design elements like the rolled lips and grove for the C clip need specialised tools to my mind, all a bit beyond the DIY in metal. As the ends locate into fixed items (coolant pump and thermostat housing I would have though the overall length would need to be accurate to well under 1mm!

Good luck.

View attachment 80086View attachment 80087View attachment 80088


Andy
@Andrew
I probably, underestimate the challenge, but worth a try. I need to get a good, long look at the beast in situ, so will talk to my indie. Missed opportunity, as it was in for service and MoT(passed) on Wednesday!
Mac.
 
Thanks @Exe_Chris - just about to get the coolant pipes (DEATH PIPE) and THERMOSTAT HOUSING (COOLANT REGULATOR HOUSING) replaced on my 1.6 FSI (I'm now running the ProBoost ECU), so wonder if you know the part numbers of those other two parts you mention?
Apologies for the tardiness of my half promised reply, but it will save you a lot of money.

In my mind there is little doubt that Audi use Mahle as their supplier of the FSI thermostat housing. I bought one from PIM (credit to Nod for the original link some time ago) and it is clear the Audi branding has been scratched out, look at the second picture, the top line was the Audi circles and the second the part number.

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Notice you get the lot, housing, thermostat, coolant temperature sensor, and block seal.

Now price, I expect Audi will be around £300 (no doubt a bit cheaper with TPS if available to you) and PIM's price £90 (including current eBay 20% discount code), your choice!


I remember Mahle also do a bundle with the death pipe.

Hope this is of some use.

Andy
 
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Thanks Andy. Really appreciate it. I'll share it with my mechanic! Hopefully he hasn't already ordered these parts.
 
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