8 replies to this topic

[rawky]

Hello there,

I went to replace my thermostat today, and when I tried to remove the last of the three thermostat bolts the head rounded. I went down one mm in size and tapped the ring end of a spanner on, even then the bolt would not budge and then rounded again. Now the head is as good as circular and the bolt has not budged...

What would people say I should do? I haven't had this problem before...

I'm guessing;

• Cut the hex head off
• Take the housing off
• Try and move the remaining section with two nuts turned together as per a head stud
• If that fails, drill it out and tap a new thread?

Cheers!

[L400RAS]

That sounds about right, however before you drill it out, try mole grips on the shaft to turn it out. With the thermostat housing out hte way, heat up the surrounding area of hte head with a blow torch or similar to expand the head away from the stud.

[rawky]

Can I get a new bolt from a local hardware shop or do I have to get one from MiniSpares?

[L400RAS]

I assume you have a sandwich plate under the thermostat housing, and you do require an actual bolt, (earlier non sandwich plate housings were only held on with studs and nuts)

You require part number DAM7760. If you can find one locally you need a 5/16 UNC x 2 1/2'' long - length is critical.

[Nu2mini]

................... With the thermostat housing out hte way, heat up the surrounding area of hte head with a blow torch or similar to expand the head away from the stud.

Take Care Here !!!! Antifreeze is flamable even when diluted. So only do this if you have already drained the system. Do NOT put any flame near it if you still have antifreeze in the block !!.

You may find it's actually seized in the sandwich plate and not the block. A safe alternative here is to sacrifice the sandwich plate cutting it close to where the bolt is inserted you may then be able to extract the bolt from the head

[bobs]

Good luck heating the head up with a torch!!!

To be honest this is how people use heat torches incorrectly, it won't do much heating the head up, and you won't get it hot enough for ages, probably causing damage and it'll still be stuck tight most of the time.

Now this may sound backwards, but it's how you loosen bolts with a heat torch easily and quickly.
You heat the bolt, that expands and contracts in the thread hole, breaking any rusty or stuck parts, and then you work the bolt out slowly with some grips whilst cool/cooling.

I'd try the two nut technique first, use heat as a last resort, as mentioned above have a fire extinguisher handy!

Edited by bobs, 23 August 2011 - 08:23 AM.

[Bodhi]

Any body and luck with this problem using a heat gun instead of a. Blow torch?

[Icey]

I assume you have a sandwich plate under the thermostat housing, and you do require an actual bolt, (earlier non sandwich plate housings were only held on with studs and nuts)

 

I use studs and nuts with a sandwich plate, no issues.

 

 

 

 

Any body and luck with this problem using a heat gun instead of a. Blow torch?

 

Heat gun won't really get hot enough, you can try but I doubt it would have any effect. Chances are the bolt gets hotter with the engine running than you'd manage with a head gun.

Edited by Icey, 30 September 2015 - 11:43 AM.

[jaydee]

Hello there,

I went to replace my thermostat today, and when I tried to remove the last of the three thermostat bolts the head rounded. I went down one mm in size and tapped the ring end of a spanner on, even then the bolt would not budge and then rounded again. Now the head is as good as circular and the bolt has not budged...

What would people say I should do? I haven't had this problem before...

I'm guessing;

• Cut the hex head off
• Take the housing off
• Try and move the remaining section with two nuts turned together as per a head stud
• If that fails, drill it out and tap a new thread?

Cheers!

 

 

Try a nut splitter adding some sort of extension to apply more leverage.

If all fails, cut the head, remove the bolt, and use a tap to clean up the threads this way you can see if threads are still good or not.