danielhf
Veteran Member
So I have been experiencing horrible boost-related issues for the better part of the last 7 months. It originally started with my tune from Jeff. My RC5 was a 30psi-ish tune, but I was never able to make it hit 30psi. Months later, I was trying my first tune from vwmikel. It was set to be a 26psi tune. After two days of having the tune, I was only able to hit about 24psi.
I had been hearing from Jeff it was a boost leak with similar words from Mike. I tested my intake piping, couplers, and clamps multiple times to no avail.
After a month or so of 24psi max boost, my new max had somehow become 20psi. And then a month later, my new maximum boost pressure had fallen to a maximum of 10psi!
I was convinced it had to be an actuator issue, a problem with my N75 valve, a problem with my MAP sensor, or stuck vanes. I got together with fix_until_broke to test the actuator with his Mighty Vac. We found perfect response (to my surprise). With the vanes and actuator out of the question, we tested the N75 with a vacuum gauge during driving as well as comparing it to a known good N75. It was requesting proper boost! We also swapped MAP sensors without luck.
One strange thing we discovered during driving the car was that if it was floored for 10 seconds we could get the car up to 18psi, but after about half a second of 18psi, boost would fall to 8psi without any audible air discharge. This symptom disappeared within a few days and I was only able to hit 10psi no matter what.
I then pressure tested my system from the turbo outlet to right before the intake. It seemed like it was holding pressure, but I was convinced I felt airflow near the intercooler which has welded elbows on it for ease of piping. I figured one of the welds must have cracked, so I pulled the intake and found this:
I figured I must have a broken core. This was likely caused from impact with the ground when the car was a bit lower. But when I pressure tested the FMIC, it all checked out up to 20psi (when one of my plugs blew out from the boost pressure and was lost somewhere in my work space).
I then called up my friend Jon who owns a local shop and specializes in VW repair. He had a smoke tester which seemed like a great idea. For those who don't know, a smoke tester is a machine which pumps pressurized smoky air into the intake of the car so that any holes in the system will literally smoke and reveal themselves.
I took it over to Jon's shop and we connected the smoke tester. Immediately, we noticed smoke coming from around where the turbo was. At first I thought it must be a hole in the compressor housing, but Jon pointed out that it looked like it was coming from the intake. When we looked down at it with a light, indeed there was a hole! This is what we found:
This was one spot that I would never had been able to test with the process and tools that I had been using. That's a win for the smoke tester. It looked like a pretty big hole but I couldn't tell without taking the intake out. This I knew would be a pretty hard task. This was Matt Whitbread's first manifold he had ever designed, and it's not exactly the easiest thing to take out. In fact, due to the placement of the runners, we had in the past had to take the turbo and header out to remove the intake. Here's what I had to deal with:
I made some extremely low profile tools to attempt to remove the intake with from 1/4" allen bits, a Dremel, a 1/4" wrench, and some JB Weld:
Turns out that they worked perfectly and I was able to remove the intake without pulling the turbo (which is extra hard with the 4motion transfer case/matched downpipe). Here's what it looked like when I got it out:
I had been hearing from Jeff it was a boost leak with similar words from Mike. I tested my intake piping, couplers, and clamps multiple times to no avail.
After a month or so of 24psi max boost, my new max had somehow become 20psi. And then a month later, my new maximum boost pressure had fallen to a maximum of 10psi!
I was convinced it had to be an actuator issue, a problem with my N75 valve, a problem with my MAP sensor, or stuck vanes. I got together with fix_until_broke to test the actuator with his Mighty Vac. We found perfect response (to my surprise). With the vanes and actuator out of the question, we tested the N75 with a vacuum gauge during driving as well as comparing it to a known good N75. It was requesting proper boost! We also swapped MAP sensors without luck.
One strange thing we discovered during driving the car was that if it was floored for 10 seconds we could get the car up to 18psi, but after about half a second of 18psi, boost would fall to 8psi without any audible air discharge. This symptom disappeared within a few days and I was only able to hit 10psi no matter what.
I then pressure tested my system from the turbo outlet to right before the intake. It seemed like it was holding pressure, but I was convinced I felt airflow near the intercooler which has welded elbows on it for ease of piping. I figured one of the welds must have cracked, so I pulled the intake and found this:
I figured I must have a broken core. This was likely caused from impact with the ground when the car was a bit lower. But when I pressure tested the FMIC, it all checked out up to 20psi (when one of my plugs blew out from the boost pressure and was lost somewhere in my work space).
I then called up my friend Jon who owns a local shop and specializes in VW repair. He had a smoke tester which seemed like a great idea. For those who don't know, a smoke tester is a machine which pumps pressurized smoky air into the intake of the car so that any holes in the system will literally smoke and reveal themselves.
I took it over to Jon's shop and we connected the smoke tester. Immediately, we noticed smoke coming from around where the turbo was. At first I thought it must be a hole in the compressor housing, but Jon pointed out that it looked like it was coming from the intake. When we looked down at it with a light, indeed there was a hole! This is what we found:
This was one spot that I would never had been able to test with the process and tools that I had been using. That's a win for the smoke tester. It looked like a pretty big hole but I couldn't tell without taking the intake out. This I knew would be a pretty hard task. This was Matt Whitbread's first manifold he had ever designed, and it's not exactly the easiest thing to take out. In fact, due to the placement of the runners, we had in the past had to take the turbo and header out to remove the intake. Here's what I had to deal with:
I made some extremely low profile tools to attempt to remove the intake with from 1/4" allen bits, a Dremel, a 1/4" wrench, and some JB Weld:
Turns out that they worked perfectly and I was able to remove the intake without pulling the turbo (which is extra hard with the 4motion transfer case/matched downpipe). Here's what it looked like when I got it out:
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