Fixing Vacuum and Boost Leaks on 2.7 Turbo Audi

This is a video of working to remove the intake manifold to repair some small vacuum leaks as well as replacing a ripped throttle body boot with a silicon type heavy duty one because the torn boot was creating a large boost leak. We are replacing any zipped vacuum lines with properly sized hose clamps.

A well-maintained engine will take you far and the c5 Audi a6 is no exception. This model is from the year 2000 so it does have some use and with the age, although it was a relatively low mileage car when I acquired it, she was not without some basic maintenance needs. Over my time of ownership, I replaced the secondary water pump, main water pump & timing belt, lower control arms, tires, radiator fan, and hid headlights (the old ones were hazy beyond feasible repair), in doing this I decided to add a chipped (reprogrammed) ecu (engine control unit) or ecm (engine control module). I did do other small items here and there to make her look extra clean and a bit personalized like window tint, debadging the rear emblems and replacing the front grill with a black metal one that had to be custom trimmed out from the factory grill.

These cars are quite prone to boost and vacuum leaks mostly due to the age and engine heat buildup in the compartment causing the plastic fittings and rubber hoses to become brittle over time. Chipping the ecu to add more boost doesn’t help and can cause additional boost leaks relatively quickly (especially if you have a heavy foot). Even before the chip I have had the boots pop loose around the intercoolers and these can even be tricky to get to due to all the extra plastic trim and covers that can be in the way. Once you remove the lower splash guard and sometimes even the wheel well covers working on these Audi’s becomes a lot easier when you have the right tools and organization in place.

After chipping the ecu the car performed very well with the aforementioned modifications for a good while, but I never really floored it much, especially not in between shifting so as not to allow boost to build up and pop the hoses prematurely. I never drag raced it or ripped on it, just kept that extra boost for use in highway passing situations under partial throttle. Besides an additional feature of the reprogramming adjusted the drive by wire system to cause the throttle body to become more responsive at mid throttle really waking the car up for everyday power needs. I probably could have squeezed some more power out of the car by upgrading the exhaust, but I really liked the stealthy quietness of the stock setup and I felt like I had already approached a healthy spending limit on the car given it’s resell value.

Be that as it may eventually I did manage to pop the throttle body boot, after it came loose once before; I tightened it down harder and it eventually gave out. These cars you can tell right away when you have a large boost leak because they become very sluggish and you can hear a large hiss from the engine area from the pressure escaping when giving it gas. These cars are equipped with twin turbochargers with electronic wastegates and a dual diverter valve boost recirculating system. Meaning, unlike on other turbo cars that use bov (blow off valves) they do not hiss or let the pressure out when you snap the throttle closed, instead the dv’s divert the boost back through the intake y pipe and intercoolers until the pressure goes down enough to close the valves again or the throttle is pressed. The reason I bring up the differences between bov and dv setup is because the smaller leaks on vacuum hoses and fittings near the intake manifold can be a lot harder to notice and find. Reason being if you are not very experienced with these cars you could think it has a bov when these smaller leaks are present because the car wont necessarily feel very down on power and you get some hissing on snap closing the throttle, similar to a traditional bov type turbo venting setup.

Luckily, I had ordered a set of silicon boost couplings as a backup in case I tore any hoses. And when I first tore the boot I just thought it had a loose hose or leaking manifold fittings because on initial inspection I could not see a tear on the tbb (throttle body boot). Mainly because it was near the bottom side of the hose, and also these cars do have a lot of extra components and engine trim pieces in the way that make it difficult to find the leaking culprit without removing multiple components.

In retrospect it would have been much easier to find the leaks with a smoke machine that puts inert gasses through your engine to find where the air is escaping. I have since acquired one to make future repairs and diagnosis a quick and easier process. Time is money after all!

So here is a video of the repairs “Fixing Vacuum and Boost Leaks on 2.7 Turbo Audi”, where I begin working to remove the intake manifold to address some hoses and fittings that I knew needed some attention and it was upon this further disassembly that I found the main culprit, the ripped tbb.

I left out some of the basic parts of getting started like removing the engine trim, disconnecting battery, removing intake tube and y pipes because I felt like most people who would be doing this service have at least some level of competency in mechanical work and experience in removing these rather easy to get to pieces of the repair.

Also, while I was at it, since I already had to remove the manifold I decided to remove and clean out the “Spider Hose”. This is a 3-way splitter plastic hose that works by joining the pcv (positive crankcase ventilation) ports at the top of the two valve covers and one under the intake manifold to recirculate the fumes (and sometimes engine oil when restricted) back through to the y pipe for emissions.

Another side note, normally you would have to remove the sai (secondary air injection) system which sends air to the catalytic converters to warm them up faster to do this repair. But I had already removed the pump and upper hoses (located under the y pipe near the rear of the engine) from a prior modification. The engine codes for the sai and rear catalytic converters were coded out as part of the ecu reflash.

After replacing the torn boot, cleaning the Spider Hose, properly sealing all the vacuum lines and fittings she is running tip top with plenty of power and piece of mind and no more hissing from escaping boost.

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