Block thread stripped on '96 850 !

karltheozy · Post by **karltheozy** » 08 Mar 2011, 19:53

Help ! - - , Late Sunday evening , Hard day on a Blown head gasket on Son in laws three month owned 850 wagon ( '96 ) ,
We are fairly Tired and I am tightening the Tenth head bolt for the last time ( Haynes Manual suggests get to 44 ft lb then pull the torque wrench through 130 degrees ) , - - - - - the Bolt loses Torque - -and I am thinking It must be the softest Bolt thread snap in history - - !!!

When the bolt is removed it has Aluminium threads wrapped round it for the last 25mm !!

We packed up and went to think ! - - The Plan now is to re-thread the hole in the block one size larger - - then use a new - -but slightly larger Bolt .

Has anyone done this before - - - , should we use a "Helicoil" ( Possibly called a Threadcert or some such O'seas ) - -or possibly just scrap the motor completely - - - . The motor had some water in the Oil before the Fix was tried .

Any Ideas on this one ?? , Son in law needs his Car ASAP .

Post by **JDS60R** » 08 Mar 2011, 20:12

Use a time-sert only - Do not go oversize on one head bolt - Do not do it.

Post by **jimmy57** » 08 Mar 2011, 21:42

Do what he ^^^^^ says. You know finding a bolt the right size and length, much less the right strength, is going to be about impossible.

karltheozy · Post by **karltheozy** » 08 Mar 2011, 22:04

Now - - rather scared to ask the next question - - - and until I have thought a lot more about this - - - Can you answer another Question ( any of the current responders would be OK - - - -) , Why would an Insert be better - - is an Insert not Just another Bigger Bolt

??.
The vehicle is some distance from the Engineeering suppliers and the Cost of a new Engine begins to look better
after you have Paid a few hundred Dollars for the Insert Kit - - -. ( Probably have to source that kit from the USA or the UK ).

Post by **JDS60R** » 08 Mar 2011, 22:45

An insert allows the use of the same size bolt. It is a stable element that replaces what was removed(stripped threads. ThIs provides the ability for you to match the holding and expanding of with each of the identical bolts.

A larger bolt ( if it fit) would be the exact opposite. It would throw the equality out of balance. Because it has a different mass it would heat up different , expand different and cool down different. It would even stretch different over time.

Think of the expansion rate of the bolt. If you have one different than the others it will load and stretch different . In some areas it may not fit. An insert restores the threads without enlarging the bolt. The bolts fatigue over time. Most do not have the equipment to measure the stretch of the bolt or the documentation on original length. This is why Volvo requires all of the head bolts to be replaced with each replacement of the head gasket.

It is a hard lesson learned by many who try to reuse them. They always snap -buy all new ones

Post by **precopster** » 09 Mar 2011, 04:31

I have a 95 model block in good condition, (203K) that's kilometres and I'm in Melbourne, but I'm assuming yours is a 20 valver being 96 model (they went back & forth b/w 20 and ten valvers in '95-'96) I think the block/crank is the same but pistons are not.

Is it a B5254 block or B5252??

Post by **Ozark Lee** » 09 Mar 2011, 07:00

The inserts are often called Heli-coil kits. They run the the $15.00 to $25.00 range depending on the size. In an aluminum block they are very easy to install.

...Lee

karltheozy · Post by **karltheozy** » 09 Mar 2011, 17:53

Thanks for the Explanation's - - -

1) I am in Sydney - - it is a 10 Valve Unit Wagon '96 model ( both the ones I have to maintain are Identical ) - -I have a wreck 10 valve unit ('94) on site that We could spend another Sunday or two trying to put in ( 350 K however !! ) .
2) I hope to fix this one ( after putting a complete 2 man Sunday effort and about US$200 in parts so far - - ).

3) I have enquired after a Heli coil service to put in a new Insert - - and also checked the price of a kit so I can DIY - - -. Both of these seem to be about retail US$ 150.- - ( I have arranged a kit trade buy at about A$90.- ).

Thanks for all the advice on this one I will take plenty pictures and submit them ( always assuming it succeeds ) .

Karl

1911colt · Post by **1911colt** » 19 Mar 2011, 23:26

DON'T GO OVERSIZE FOR SURE, GO THREADCERT IF YOU CAN...YOUR CHANCES OF A GOOD REPAIR ARE MUCH BETTER THAT WAY...GO OVERSIZE BOLT AND YOU WILL REGRET IT FOR SURE.