Snapped throttle body screws.

[clipper]

Removing the hot water feed to the throttle body on my mate’s 325i all three screws snapped the head off instead of unthreading.
With the feed plate removed there is about 4mm of rusty screw protruding, but we didn’t try to get them out yet. Any advice on getting them out?
My thoughts are small blow torch for very localized heat and mole grips, any better suggestions? The thought of having to drill them out terrifies me!
Before anyone says it, I know that in theory, you can simply join the tubes and bypass the TB, but we don’t want to do that permanently (we have done for the time being, but want to repair it properly).

[Tedswagon]

Penetrating fluid, heat and grips sound like the place to start. If that doesnt work, take it off and have a go on a bench. Drill out as much as you can with proper HSS Cobalt drill bits and then tap it round and round till its out. Maybe have a tap set to hand just in case!!

[arrisbmw]

get it off the car, in a bench vice, soak screws in penetrating oil from both sides if you can overnight, cut slim slot in screw with angle grinder thin blade, gentle tap flat headed screwdriver in, then undo. if that don,t work your have to go tedswagon way. but when you drill out try a small narrow hole thru the center first so you can weaken the screw, you might be able to get a thin stud remover in.
or collapse the screw inward not damaging the thread in main component.

[clipper]

Thanks.

These screws are M4. Even the finest cutting wheel on my dremel is 1.5mm thick. No way I am going to get a slot in the screw shaft leaving enough steel either side to withstand trying to wind them out.

I think we'll try the heat / grips method first, drilling with a 2 or 3mm bit is just asking for it to snap off inside the screw IMO.

[martauto]

Lets have in out on the bench and in a vice if possible so its secure to work on.
After a very good soak in penetrating fluid ( not Wd40) take a small hammer and a narrow angled punch and gently tap in the centre of the thread to try and shock it free. This you may not see happen but it does not take much.
Then with the same punch, start at the top outside and tap gently with the punch at 90 degrees to the vertical (12 o`clock) and also at 45 degrees to the horizontal.
If it moves then keep going anti clock wise keeping the punch in the same position but "walking " around the vice so to speak.
If this fails then its a drill job, trying to use stud extractors first then no more than a 3mm drill.
If this is no good then resort to Helicoils which are very good also.

Mart.