Plus gas for glow plug removal prep, which one?
Discussion
Planning on changing the glow plugs in my 1.7cdti Astra. Was going to start soaking them for a few days before to try and help them come out.
There’s 2 different ones on Amazon, which one is best? Or is there anything better than these available?
Plusgas English Abrasives 803-10 Tin 500ml https://www.amazon.co.uk/dp/B0001P02RU/ref=cm_sw_r...
English Abrasives 809-10 Plusgas Tin 250ml https://www.amazon.co.uk/dp/B0001P02S4/ref=cm_sw_r...
There’s 2 different ones on Amazon, which one is best? Or is there anything better than these available?
Plusgas English Abrasives 803-10 Tin 500ml https://www.amazon.co.uk/dp/B0001P02RU/ref=cm_sw_r...
English Abrasives 809-10 Plusgas Tin 250ml https://www.amazon.co.uk/dp/B0001P02S4/ref=cm_sw_r...
Penelope Stopit said:
How does anything run down the threads?
When you cut threads they don't mate perfectly, there is always some room between the male and female thread; this is called thread tolerance, it's designed in, and defined in the standards for the various thread types. Without this built-in looseness you'd find a lot of combinations of nuts and studs very difficult to tighten or loosen. I believe thread tolerance is even present with interference threads but couldn't swear it. Plusgas and similar concoctions all have very low viscosity so can get into these very small gaps, and they are drawn into those gaps through capillary action.
Penelope Stopit said:
How does anything run down the threads?
It doesn’t it’s bro science. As someone else pointed out, they corrode into the head, two dissimilar metals causes galvanic corrosion. Plus most are quite fine threads, and you really don’t want to be shearing glow plugs it’s a nightmare. The only reliable way is to cherry red them and squirt with cold water, this shocks them out the same as exhaust studs. The best thing is an induction heater, failing that a torch, but be careful not to damage anything in close proximity. markcoznottz said:
Penelope Stopit said:
How does anything run down the threads?
It doesn’t it’s bro science. As someone else pointed out, they corrode into the head, two dissimilar metals causes galvanic corrosion. Plus most are quite fine threads, and you really don’t want to be shearing glow plugs it’s a nightmare. The only reliable way is to cherry red them and squirt with cold water, this shocks them out the same as exhaust studs. The best thing is an induction heater, failing that a torch, but be careful not to damage anything in close proximity. Penelope Stopit said:
markcoznottz said:
Penelope Stopit said:
How does anything run down the threads?
It doesn’t it’s bro science. As someone else pointed out, they corrode into the head, two dissimilar metals causes galvanic corrosion. Plus most are quite fine threads, and you really don’t want to be shearing glow plugs it’s a nightmare. The only reliable way is to cherry red them and squirt with cold water, this shocks them out the same as exhaust studs. The best thing is an induction heater, failing that a torch, but be careful not to damage anything in close proximity. The heating/quenching approach mentioned does essentially the same thing - reduces the friction in the thread interface by increasing the thread clearance. But, heating the crap out of stuff isn't always safe, especially with a naked flame.
Donk is correct, the difference in tolerance bands between an internal and external thread mean that an assembled thread does not become a single lump of metal, and the creeping nature of penetrating oils is so they get down in there to help with lubrication.
If you're particularly bored, BS3643 is a typical standard for metric threads and you can compare the tolerance limits for different thread classes in there.
If you're particularly bored, BS3643 is a typical standard for metric threads and you can compare the tolerance limits for different thread classes in there.
donkmeister said:
Penelope Stopit said:
markcoznottz said:
Penelope Stopit said:
How does anything run down the threads?
It doesn’t it’s bro science. As someone else pointed out, they corrode into the head, two dissimilar metals causes galvanic corrosion. Plus most are quite fine threads, and you really don’t want to be shearing glow plugs it’s a nightmare. The only reliable way is to cherry red them and squirt with cold water, this shocks them out the same as exhaust studs. The best thing is an induction heater, failing that a torch, but be careful not to damage anything in close proximity. The heating/quenching approach mentioned does essentially the same thing - reduces the friction in the thread interface by increasing the thread clearance. But, heating the crap out of stuff isn't always safe, especially with a naked flame.
donkmeister said:
Penelope Stopit said:
markcoznottz said:
Penelope Stopit said:
How does anything run down the threads?
It doesn’t it’s bro science. As someone else pointed out, they corrode into the head, two dissimilar metals causes galvanic corrosion. Plus most are quite fine threads, and you really don’t want to be shearing glow plugs it’s a nightmare. The only reliable way is to cherry red them and squirt with cold water, this shocks them out the same as exhaust studs. The best thing is an induction heater, failing that a torch, but be careful not to damage anything in close proximity. The heating/quenching approach mentioned does essentially the same thing - reduces the friction in the thread interface by increasing the thread clearance. But, heating the crap out of stuff isn't always safe, especially with a naked flame.
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