Loose head bolt!!!

[Billy_rfc]

Hey guys, I've just found something that really worries me. When I've went to reinstall my throttle bodies and got the engine running again I noticed water flowing from under the throttle body heat insulator. On further inspection, the water was coming from one of the large head bolts. The bolt ain't tightening down!

Anyone got any thoughts

Billy.

[marcus1970]

Billy_rfc said:

Hey guys, I've just found something that really worries me. When I've went to reinstall my throttle bodies and got the engine running again I noticed water flowing from under the throttle body heat insulator. On further inspection, the water was coming from one of the large head bolts. The bolt ain't tightening down!

Anyone got any thoughts

Billy.

How bad is it?

Mine has been doing this (small amount of water) for around a year now - I'll get round to getting it fixed one day soon...

MB

[betty_swallocks]

Cylinder head bolts are called stretch bolts because thats what they do, the only solution is to replace the bolt with a new one, head bolts are not supposed to be used twice, if you have had the head gaskets replaced it could be that they have used the old bolts which is in my opinion false economy

has the thread stripped or is the bolt bottoming out in the hole, in which case dont be tempted to over tighten it as this will strip the thread

Edited by betty_swallocks on Tuesday 14th November 22:35

[Billy_rfc]

The bolt can be moved up and down in its hole but I cant get the bolt out of the head due to the head of the bolt not passing the casting of the cylinder head. As far as I know the heads have never been removed so must have been a dodgy bolt or its been rumped up to much.
Do you think I would get away with putting silicone around the bolt as a short term measure?

[longbow]

This is bad news. When I was torquing my head bolts down during my engine rebuild, one of the nut heads was actually slightly bent and it binded onto the stud during torquing - I tried to undo it, but it unscrewed the stud and I had to remove the head, as you said, it won't come out due to the overhang on the head (must be an inner one right?). The fact that you can move the bolt means either it has undone or it's stripped the thread in the block. Either way, you are likely to suffer cylinder leakage and coolant entering the cylinder(s), and also a warped head. The only way to repair this is to strip the head off, and this means engine out. Running the engine without a main bolt torqued down will only lead to failure as far as I can see. Also, the studs on the AJP don't stretch as in many conventional head bolt designs - the stud is designed to stay in the block as far as I'm aware. The nuts are torqued down to a given setting, and not say an extra half turn as is the case with stretch bolts (my MR2 uses stretch bolts, and there is a different procedure for those).

[Billy_rfc]

longbow said:

This is bad news. When I was torquing my head bolts down during my engine rebuild, one of the nut heads was actually slightly bent and it binded onto the stud during torquing - I tried to undo it, but it unscrewed the stud and I had to remove the head, as you said, it won't come out due to the overhang on the head (must be an inner one right?). The fact that you can move the bolt means either it has undone or it's stripped the thread in the block. Either way, you are likely to suffer cylinder leakage and coolant entering the cylinder(s), and also a warped head. The only way to repair this is to strip the head off, and this means engine out. Running the engine without a main bolt torqued down will only lead to failure as far as I can see. Also, the studs on the AJP don't stretch as in many conventional head bolt designs - the stud is designed to stay in the block as far as I'm aware

Thanks Longbow, was thinking that it would be a head off job. Your right in thinking the bolt is inside the V. I think the stud has sheared cos I can't really feel the stud catching on anything when pulling it up or down.

Will let my local guy have a look and take it from there. If the heads got to come off then RR spec heads here I come!

Edited by Billy_rfc on Wednesday 15th November 20:53