How To Service a 38MM Wastegate

How To Service a 38MM Wastegate


Wastegates are an important part of your turbocharged system and essential if you want to control your boost accurately. Over time and subjected to temperatures well over 1500 ºF in most applications, these units can fail frequently or require service.

Today I’ll be showing you how to service a 38mm wastegate, which is one of the most common wastegate sizes due to it’s relatively low cost. The wastegate I’ll be showing you how to service is a Tial, part number TIL-WGT38, although generally most 38mm wastegates are similar in design and assembly.


We’re going to be taking the wastegate apart to replace the Nomex ring inside the diaphragm, restoring boost control and the seal of the external wastegate.

To begin have a friend hold the top of your 38mm wastegate and the bottom half together. Now carefully and evenly undo the hex screws circled below.



Make sure to undo the hex screws in alternating fashion, removing the bolt opposite the one you just removed. Make sure your friend has a grip on the top and bottom halves and undo these bolts carefully. Make sure that they do not bind or otherwise damage the bolt, or the threads in the bottom half of your wastegate.


With the top half of the Tial wastegate undone, remove the top hat and the spring located inside the wastegate. You should see the diaphragm plunger as well as the ring you will be replacing. For a guide on how to service internal adjustable wastegates, check here.


Remove the small set hex screw that secures the top diaphragm assembly to the piston. Once this screw is removed, you can take off this entire diaphragm and replace the ring.


This rod is what controls the movement of your external wastegate, and the larger circle is of course the side port of the 38mm wastegate. Take this time now to inspect for any scarring or damage to this rod.

If this main rod is damaged, nicked or bent in any way, you will need to remove the smaller set screw shown above, and then undo the bolt that holds this rod in.


It also wouldn’t hurt to check the threads on the 1/8th inch NPT port located on the side of the wastegate. Chase with the proper tap if you need to clean this port up, you don’t want it leaking on you.


Flip your wastegate upside down to check the fire ring that you initially pressed into your wastegate on the first install. Check to make sure that this ring is still intact and that it doesn’t just slip out at the first chance it gets.


Pull this fire ring out and replace if it’s become worn or it’s clear that there’s a leak. Replace this ring with the Tial part number  1219FSSM.


Replace the old Tial wastegate diaphragm and install the new one, part number 3844DIAASM and reassemble your 38mm wastegate.

You now know how to service a 38mm wastegate, if you are looking for other wastegate sizes, like the 44mm, 50mm or more check our FAQ section for all the how-tos and articles you need.