the flyin' scotsman

One of the side covers (DS) on the GT intake is cracked where previous model years have the crank diag harness bolted to.
I've tested the crack with compressed air from the outside and oil (atf) from the inside and dont see if the crack allows an air leak but want to be doubly sure by welding the crack with JB weld.

Can anyone confirm the intake metal compound can be repaired in this fashion? if not, how?

polecat702

You need to take it to a reputable aircraft certified welding shop. It's a casting, and should be cleaned using ultrasound. It needs to be welded not epoxied.

polecat702

I fergot to mention, Heli-arc TIG, in a purge box if they have it.

the flyin' scotsman

The ultrasound would be a great to do just to see if the crack is fractured throughout the piece. Might be easier to find a replacement.

LostInSpace

Don't know about JB Weld, but it can be done.

I had a approx 8mm hole in my intake where one of the runners connected to the intake body after bead blasting. Had it welded up by a body shop that was familiar with alloy, just told them it was a magnesium alloy. So far, so good.

mark kibort

I would just use a good helping of JB weld on it. its not critical, especially if you are not seeing any air go through it under your test, however, a better test would be with it running and spraying brake cleaner or carb cleaner at the crack to see if the idle changes. because the intake is under vacuum, even a piece of tape could fix the issue almost permantly. . JB weld is good stuff and perfect for this type of problem.

slate blue

I welded one, you will need magnesium filler rod which are fairly expensive. Otherwise just get a used one.

Greg

docmirror

Don't hate me. I've fixed plenty of AL with JB weld. Iron castings too.

polecat702

Malolm, if you're dead set on epoxy. Find a Catapiller dealer, Cat makes the best epoxy on the market. It comes in a 2 part packet, pre measured, break the top into the bottom and away you go. It's very inexpensive.

the flyin' scotsman

The only thing I'm dead set on is curing the high idle.

I'm truly pissed that I had the intake off and didn't rebuild the intake/throttle body on a car thats 20YO and has been through at minimum a flash fire but that wasn't my decision and we are where we are.

Now I have the intake off, again and the throttle body fully apart every small item is being examined. Here's a pic of the cracked intake side plate:

polecat702

I've been paid to weld for over 45 years. That said I would either Heli-Arc it, or replace it. If you have it welded it won't ever break there again. It will need to be cleaned using ultra-sonic cleaning' if you have it welded.

the flyin' scotsman

I appreciate your insight and experience.

How do I know for sure that the crack pictured allows (or not) an air leak? I'm doing the work in a very rural part of SW Alberta, Canada so I've only my hand tools for diag purposes.............no fancy welding here.

Jerry Feather

Given the picture of the crack in question what I would do it first drill the hole all the way through the casting. Use a drill that does not drill the threads out of the hole. That is, the hole in the middle with the threads. Then I would break the piece off that is nearly cracked off anyway. Then I would grind the surface smooth. Then I would take a piece of about 5/8 inch aluminun bar stock and cut it to about the length of the piece that is not missing. Then I would drill a hole through it to the minor size of the hole with the threads in it. Then I would redrill the hole in the casting to the major size, and the with a short bolt I would bolt the new piece onto the casting from the inside. The bolt from the inside should be short enough so that you still have enough threaded hole on the outside to utilize this mounting point for its intended purpose. Use some red lok tite for this process so you don't ever end up with a loose bolt running around from cylinder to cylinder some time in the future.

I don't think this crack is causing an air leak.

Jerry Feather

polecat702

Malcolm, you should have someone that can scratch TIG it. Community collage or trade schools. Any A&P mechanics in the area for private plane repairs or maintance. You can MIG weld aluminum, but it takes lots of experance, and I wouldn't trust it for this repair. I'd be willing to bet that there are spider cracks all around that break. Remember it's a casting, which means that it's porous. It's also 20 years old. If you do find someone that can weld it, have them preheat the the piece in an oven, if possable have the whole plenum there with the side piece bolted in place Aluminum casting expand and are prone to warpage.
You may be better off buying a replacement part, because of your location.

the flyin' scotsman

The potential of spider cracks unseen by the human eye is why I started this thread. I'm a good 5 hr return trip to an airport repair type location with unknown capabilities.

Polecat.............many thx for your inputs to this thread.

Anyone have a spare to sell?