ABARTH Fiat Uno Turbo Club of South Africa

Tracing a boost leak


Tracing a boost leak

One of the most common problems experienced by many Fiat Uno Turbo owners, is what is commonly known as an “air leak”. It means that there could be a leak in one of the several rubber and/or metal pipes that carry boost, between the turbocharger and the intake manifold. I would hazard a guess and say that 90% of the time, when your car is not performing as it should, there is a leakage in one of these pipes. The Fiat Uno Turbo has quite a complex and involved boost piping system, I will try and keep this article short and to the point, yet not be too vauge in describing the particular boost pipes that I’m talking about.

What is even more scary is the fact that so few Uno Turbo owners know their way around these pipes, how to check for an air leak, or even how to identify what an air leak is. You know you have an air leak when your boost gauge is showing the boost, the revs are there, everything is going nicely but the car is just not chucking like its supposed to. You will also hear a distinctive whooshing sound when the turbo is boosting. That’s because the most of the boost that the turbo is producing, is not going into the intake manifold as it’s supposed to, but rather getting blown into atmosphere by some anonymous leak in your car’s pipework. Let’s go through all these pipes in more detail, shall we?

You will need the following tools:

  • Flat nosed screwdriver
  • 10mm wrench
  • 13mm wrench

Dark Blue Pipe

We’ve all seen it, it’s the one right at the top, that connects to the intake manifold. From here, it connects to a metal pipe (Yellow pipe) which runs down vertically at the front of the engine, with two small pipes sticking out on the right. We’ll come back to these ones later. This pipe often cracks at the bottom, right above the cambox cover, due to engine heat. Easy to spot, expensive to replace. If this one is your culprit, it makes the most sense to replace it with a nice shiny stainless boost pipe.

Red Pipe

This connects the yellow pipe and the intercooler. This pipe does not often give problems, although it has been known to crack or burst from time to time.

Green Pipe

This pipe connects the intercooler to the metal pipe that runs underneath the gearbox (Mk2 Uno Turbo) or over the gearbox (Mk1 Uno Turbo). It has been known to give problems often, especially on the Mk2 Uno’s, since there it has a 100° bend just next to the intercooler, and it’s quite close to some sharp pointed objects like the intercooler mountings, etc.

Light Blue Pipe

This pipe is mentioned here, since this is the pipe that you need to change to 50mm aluminium/stainless steel if you want a nice performance increase on the standard turbo. On larger turbo’s this increase is a must, especially since you’re most likely going to have a bigger intercooler fitted along with the bigger turbo. It is also advised to run this pipe over the gearbox, as you can save a significant of lag by doing this – seeing that your boost pipes will be significantly shorter.

Purple Pipe

Unfortunately this pipe is quite small on the diagram, since this is very often the bugger which will make your car lose power, and very often this is the last one you check. Make sure it’s on tight, and check it now and again. It likes to tear along the side (top to bottom).

Orange Pipe

Not really known to give problems, this pipe connects the recycling valve (ie standard valve which gets replaced by an aftermarket dump valve, should you decide to modify your car) and the (yellow) metal pipe mentioned above. If you’re going to fit a dump valve, this pipe is done away with, and you block off the hole for the recycling valve with a welsh plug.

Neon Green Pipe

This one is quite often the culprit, since it becomes hard and cracks, mainly due to engine heat. Check it thoroughly. It connects the intake manifold and the auxillary air valve. The auxillary air valve is used to regulate cold starting.

Pink Pipe

Often forgotten, this little bugger is situated between the yellow metal pipe and the auxillary air valve. Does not get hard and solid as often as the neon green pipe, but don’t forget to check it before giving up.


Ah… so you’ve checked everything else, and you still can’t find the air leak? Sometimes, due to excessive boost, the plastic caps (marked in light purple) on the sides of the intercooler cracks, or breaks loose from the intercooler core. This can really be hard to find, since you have to physically remove the intercooler in order to inspect it properly. Luckily once you replace the intercooler with an aftermarket one, you don’t need to worry about it anymore, since aftermarket coolers have metal tanks attached to them, not cheap plastic ones.

What about if you’ve spent hours checking everything, and still come up empty? Have a look at the pipe between the intake manifold and the brake booster, and the one way valve that fits into the booster. It could be that either the pipe is torn or has a hole in it, the one way valve is broken (to check, take it off and suck and blow – air should only flow in one direction) or the rubber seal on the brake booster is worn, causing the valve not to seal properly.

I hope you find the problem now that you’ve come to understand the boost pipes of your car – just always remember that you need to disconnect the earth terminal of the battery before you start working on anything else. Do not blow up your airflow meter, since they’re scarce and expensive. If you feel uncomfortable working on your own car, rather have a reputable workshop check it out – it will cost you more money, but at least you have someone else to blame if something unexpected goes boom :)