18 replies to this topic

[jime17]

Hi all. Hope you can advise....

I want to do this to the turbo housing on my mondeo tdci as the variable vanes mechanism is sticking, throwing up fault codes and going into limp mode.

I've freed it off and the fault goes away for a while so I know that's the issue.

However I want to try this solution...

https://youtu.be/SFDMd8eVVXo

Which will make for better access and more thorough cleaning than unbolting the cat and trying to squirt plus gas around the bend to where it is required.

I've got a right angle drill attachment, a 6.8mm drill bit and M8 tap coming.

Any pointers for doing the drilling and tapping without ruining the turbo housing would be really appreciated.

Thanks. Jim

[Fast Ivan]

a HSS drill will do the job

center punch where you intend to drill the hole

use a constant firm pressure when drilling, avoid taking the pressure off allowing the drill to rub

no need for a coolant or cutting fluid

get a friend to hold a hover near to extract as much swarf as you can

chamfer the hole to remove burrs and to provide a good lead for the tap

try and keep the tap as square as you can

remember to reverse the tapping action to break swarf (not critical with cast but good practice)

[jime17]

Thanks Ivan. What do you mean by reverse the tapping action?

[Fast Ivan]

Thanks Ivan. What do you mean by reverse the tapping action?

 

its probably best described by seeing it done, have a look on youtube for tapping technique

[jime17]

How about sealing it. I was going to use an old caliper bolt that has a flanged head and a copper washer. Any other ideas?

[Northernpower]

Thanks Ivan. What do you mean by reverse the tapping action?

When you cut a new thread with a tap the tap cuts out the metal (from the casting on your case) in a sliver. For a clean thread you need to brake this sliver off. You do this by turning the tap a half a turn and then turn it back a quarter of a turn, the action of reversing the direction of the tap breaks off the sliver of metal. You then turn it another half a turn and back a quarter and so on until you've cut the thread all the way through. Because of the brittle nature of cast iron its not quite as important to do it because the slivers of metal will very often break off but it still good practice to do it.

[jime17]

Ahh makes sense. I've read that you tap cast iron dry. Would you guys go along with that?

[Northernpower]

Ahh makes sense. I've read that you tap cast iron dry. Would you guys go along with that?

Yes I would. Cast iron has graphite in it therefore as far as tapping is concerned (slow speed low if any heat generated) to a point its self lubricating.

[jime17]

Thanks again. Do you think a copper washer should seal ok against a flat surface? I don't want to be torquing the bolt up too much. I'm using a 1.25 pitch thread which I believe is coarse?

[Northernpower]

Thanks again. Do you think a copper washer should seal ok against a flat surface? I don't want to be torquing the bolt up too much. I'm using a 1.25 pitch thread which I believe is coarse?

A copper washer will be fine but there are two caveats, the first and most important one is you must drill and tap exactly perpendicular to the housing. If you don't you'll end up with the face between the bolt head and the housing being a taper and as a consequence you'll struggle to get a seal. To get a good face I suggest filing a flat on the housing before you start drilling. The second and no where near as important, the washer needs to be very soft. This is easy to do, all you need to do is heat it with a blow lamp until its cherry red and then let it cool slowly. If you don't have a blow lamp a gas ring on the hob will do the same job (just don't drop it on the kitchen worktop to cool  ).

 

A 1.25 pitch will be fine.

 

Having just looked at the video the other thing I would suggest is, cut the bolt length so its just long enough to go through the housing. If its too long you'll end up with a carbon deposit on it and this could end up making it quite difficult to unscrew and in a worse case scenario could damage the threads. 

Edited by Northernpower, 31 January 2017 - 04:39 PM.

[jime17]

Thanks. That all seems sensible. I'll let you know when I've drilled an oval hole at 45 degrees and snapped the tap off in the hole. 😕

Edited by jime17, 31 January 2017 - 06:15 PM.

[Northernpower]

With skills like that you could get a job in the Far East making copy parts.

[jime17]

Did you like the you tube guys big reveal? "You're gonna love this"

[Northernpower]

Yeh it was great. I use the same for cleaning out exhaust ports prior to porting and rebuilding heads.

[jime17]

I just thought of something. Would using a centre punch be likely to crack the casting or am I over thinking it?