36 replies to this topic

[WimpyMiniMan]

Hi guys, I'm replacing the radiator on my 89' mini city e 1000 and I thought I'd also replace the thermostat - whilst I was taking off the housing one of the bolts sheared however the housing came off no problem. My question is once I've drilled out the old bolt which won't be a problem once I've made a brief visit to the local hardware store to get a harder drill bit, do I replace all three bolts with the more traditional stud and nut set up or do I just go with bolts?

Cheers
George

[Spider]

Without seeing the T'stat Housing I can't be 100% sure in saying this, however I'd suggest that a replacement housing maybe in order. Sure, you can probably drill the broken bolt out OK and refit it, but I'd guess that the reason this has occurred is advanced corrosion of the T'stat Housing. It may occur again quite quickly.

 

I always fit Bolts to the T'stat Housing these days, if or when corrosion starts, I've found I've got a MUCH better chance of getting it all apart without the need to break the T'stat Housing, which is actually harder to do than it sounds - without damaging the head or more so, the threaded holes for the bolts, they can break fairly easy. I also make a point of greasing the bolts (any grease will do, no need to use some expensive stuff) every single time they are out.

[nicklouse]

The main issue is that when designed it was normal practice to do a few things at the start and end of winter in the UK these were change the oil to winter/summer grade, change the coolant from winter/summer concentration, change the thermostat from the winter/summer opening temp and finally fit the winter/summer tyres.

Changing the thermostat two times a year does a few things. The housing does not get corroded in place. The studs get a bit of oil on then two times a year. And studs were used as then you were reducing the chance of damaging the head.

Aluminium oxide is quite easy to dissolve if you can get the agent down the bores. That is why I like nuts and studs over bolts.

[WimpyMiniMan]

I think I will go with studs and nuts - the housing isn't damaged and the thread in the housing isn't that important when using studs and nuts as the pressure is generated between the stud in the head and the nut and washer on top of the housing, not the stud threading through the housing. I will of course apply liberal grease and also i have a new housing gasket which I will use when I refit.

Thanks Again
George

[Richie83]

Can see the case for nuts. I went for stainless bolts in the end though. Not that this is fool proof, but way better than standard bolts.

[gazza82]

There is no thread in the housing ... ???

[WimpyMiniMan]

There is no thread in the housing ... ???

That's makes me feel better :) thought mine was stripped!

[WimpyMiniMan]

Can see the case for nuts. I went for stainless bolts in the end though. Not that this is fool proof, but way better than standard bolts.

Yes I can imagine stainless is better than standard but I think it's almost impossible to shear a stud since the tightening is on the nut not the stud - either are probably sound options I'm just thinking worst case scenario in terms of rust.

Thanks for all the comments.
Cheers
George

[dklawson]

Stainless is only better if there is no leakage of coolant around the bolt shank, head, and t-stat housing.  You can actually set up a worse galvanic corrosion cell with stainless fasteners if you are not careful.  I use stainless bolts covered top to bottom in anti-seize compound (I believe in the U.K. you refer to this as copper slip).  I also apply gasket sealant to both sides of the t-stat housing gasket.  

 

My suggestion for your existing t-stat housing is repeated gentle heating with a torch followed by quenching the stuck bolt with penetrating oil.  As mentioned above, there are no threads in the housing so you want to work that penetrating oil down into the gap between the housing and bolt so you can break it loose and remove it. 

 

So where did the bolt break?  If it is stuck in the housing, were you able to unscrew it from the block before it bound up?

Edited by dklawson, 17 January 2016 - 03:08 PM.

[1984mini25]

Can see the case for nuts. I went for stainless bolts in the end though. Not that this is fool proof, but way better than standard bolts.

 

Stainless steel bolt + cast iron head + a few heating and cooling cycles + coolant leakage/moisture =

[WimpyMiniMan]

Stainless is only better if there is no leakage of coolant around the bolt shank, head, and t-stat housing.  You can actually set up a worse galvanic corrosion cell with stainless fasteners if you are not careful.  I use stainless bolts covered top to bottom in anti-seize compound (I believe in the U.K. you refer to this as copper slip).  I also apply gasket sealant to both sides of the t-stat housing gasket.
 
My suggestion for your existing t-stat housing is repeated gentle heating with a torch followed by quenching the stuck bolt with penetrating oil.  As mentioned above, there are no threads in the housing so you want to work that penetrating oil down into the gap between the housing and bolt so you can break it loose and remove it. 
 
So where did the bolt break?  If it is stuck in the housing, were you able to unscrew it from the block before it bound up?

The bolt is stuck in the head not the housing just drilled through it but still can't seem to get it out.

Edited by WimpyMiniMan, 17 January 2016 - 04:16 PM.

[Richie83]

Can see the case for nuts. I went for stainless bolts in the end though. Not that this is fool proof, but way better than standard bolts.

 
Stainless steel bolt + cast iron head + a few heating and cooling cycles + coolant leakage/moisture =

I've not found it to be a problem to be honest.

[Fast Ivan]

are you using an easy out/stud extractor?

if not then drill out to the tapping size then gently tap out the remaining threads, should come out like a spring, you should really clean the threads up with a tap as well.

[Blatherskite]

Apparently you can get twist drills with left-hand thread, and others reccommend these. Not only do you bore out the bolt, but have a good chance of winding the remains out as well.
Problem with easi-outs are they expand the hole as you twist, and if they break... so hard, almost impossible to shift.

[Spider]

 

The bolt is stuck in the head not the housing just drilled through it but still can't seem to get it out.

 

 

I'd suggest heating it, but I'd warn against using an extractor tool that may cause the broken stud to expand.

 

If there's something there to weld to, weld a bolt or nut to it and usually, that's enough heat to release it.