Is it common for the head bolt threads in the block to fail, resulting in a head gasket leak? Our 2003 RAV4, with about 180k miles, started overheating on a trip. The mechanic pulled the head to replace the gasket, resurfaced and vacuum-tested the head, and when replacing the head bolts found the threads were stripped on two of them. If fixed with a helicoil, are the repaired threads likely to fail again?
Are You Original Owners Of The Toyota ?
CSA
A Helicoil insert is an effective way to repair stripped out threads in an engine block. I’ve done it many times and have never had a problem with the Helicoil failing.
Here’s an interesting article about repairing stripped out threads in an engine block utilizing a Helicoil insert. http://motorage.search-autoparts.com/motorage/article/articleDetail.jsp?id=660029&pageID=1&sk=&date=
Tester
In a perfect world, they would install Heli-coils at the factory…But today, very, very few heads are ever removed, especially from Toyota engines, so they consider the factory assembly to be permanent…
It could be that severe overheating (and not stopping the car) led to a severely warped cylinder head. This in turn could cause some of the the threads to pull and when the head bolts were removed the threads were finished off.
A Heli-Coil is a perfectly acceptable method of thread repair, among several others, and should not be a problem.
Owned since new, never had an issue with overheating.
Would it be advisable to put helicoils in all the bolts now before replacing the head?
Hey tester, you noted that some head bolts can not be re-tourqued due to streaching. I am wondering if this engine requires the head bolts to be repaced with the head gasket? Just curious.
Most modern engines now use Torque To Yield (TTY) bolts that are intended to stretch a specific amount as they are tightened. They should always be replaced if they are removed.
As long as the bolts can be properly torqued, that’s all that counts…Installing helicoils in all of them would be expensive and not necessary…
People that used to race midgets with air cooled VW engines used to put helicoils in all the spark plug holes just because their steel threads made spark plug changing so much easier. I had an air cooled 71 Bus and every time I changed the plugs it felt like you were crossthreading them in those aluminum heads.