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Recently I was noticing my boost gage would hit 20 psi at WOT. I also had an exhaust leak at the header collectors. So I decided to tackle all issues at once. First I removed the wastegate to check when it was opening and at what pressure. It would stay sealed until 9-10 psi and then lift off the seat. There was smooth movement and it was not sticking.
I attached a pressure gauge with a valve stem and slowly built up pressure. I also verified that the diaphragm would hold pressure. I used a low pressure natural gas gauge to measure.
I noticed quite a bit of carbon build up so I removed the valve and separated the pressure chamber. Once I got the valve out and cleaned the carbon off I noticed the valve seat had a crack. After reading on the forum I learned the valve seat was a loose fit and was held in by the crossover flange as well as carbon build up. Sure enough as soon as I gave it a few taps the seat gradually worked its way out.
A question I have is that I thought that the stock wastegate starts to bleed pressure at 4 PSI, how many springs are in the diaphram? Mine has two, the big one that is in the bell chamber and another one that rides around the valve stem. Did someone add this second spring? is that why mine is holding pressure until 9-10 psi?
Great info. Someone must have added the small spring, never seen that before. Seems like it would restrict flow through the wastegate. And I’ve had a stock wastegate with three shims between the valve housing and diaphragm hit 20psi for three seconds when my makeshift vacuum line melted. It also melted the catylitic converter and cracked the headers and crossover. It broke two flanges right off, one header and one on the crossover. Lots of damage in three seconds. Are you still using the stock wastegate control valve?
Thanks for posting this! If you have any more pics or more info on disassembling the wastegate, I'd love to hear more. There's not much info out there on them.
Back in the day, I used to sell a few parts and send cores to Tim @ SFR and I pointed out that on some of the cores (that I discarded) the seat was cracked and warned him to be on lookout for this before he refunded core charges.
Wasn't worth it to me at the time to even find a new seat but this is some good info for those that want to keep the stock WG functioning for years to come.
11-07-2018, 08:45 PM
Waste gate refurb
