Evo VI – Boost Problems

(First posted on MLR forum in October 2015)

A problem I had 2-3 months ago…

This must have been a gradual problem but eventually had got to a point where the car felt to be lacking a bit of grunt. So my wife and I took the Evo out one evening so she could watch the boost gauge properly to see what it was doing. It wasn’t completely consistent but it was tending to settle at 1 bar. It should have been holding 1.4 bar.

I was a bit concerned at first as the boost control solenoid and actuator are new so it can’t have been caused by either of them right??? Not wanting to get too carried away pulling the turbo off or anything drastic like that I thought I’d better have a nose under the bonnet for anything obvious.

One evening after work I got my head in the engine bay. Oh, then this chicken wondered in off the road. I’d say it must have been lost but it seemed to be very sure of it’s destination.


Anyhow, I removed the solenoid and checked it was working, pulled it apart and found nothing wrong with it.

IMAG3295_zpsueqer11c (1)

It was fitted on an anti vibration mount because I could hear it clicking in the cabin when I first fitted it. So when I refitted it I fitted it solid to the turret again so I’d be able to hear if it was being operated by the ecu. It was clicking as expected so that ruled out any ecu/wiring troubles.


I did a boost leak check next which would also check the actuator was moving when boost is applied. No leaks so not that but…


I had a closer look at the actuator and noticed it wasn’t under tension at rest so clearly that wouldn’t be holding the wastegate shut. So I took it off, not a fun job…


This is what I found inside


As it had been on the car less than a year and only a few thousand miles I wasn’t particularly impressed. Basically water has got in and the piston had unscrewed from the rod, effectively lengthening it and reducing the pretension eventually to the point there was none at all.

I gave everything a good clean and inspection but didn’t really want to just reassemble it all as it still didn’t look great.


I emailed Forge a few pictures and they were very helpful. They sent me a complete kit of new internals so I can’t complain too much really though I could have done without the hassle of the problem and time repairing it.


Back together


It came with the piston threadlocked onto the rod and some grease in the rubber seal to help stop water getting in again. I decided to add a cable tie to make sure it is sealed on the rod. I think this will do the job fine and it shouldn’t suffer the problem again.


With it all back together I got all my torques and horses back.

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