Toyota Hilux/Hiace 2TR-FE 2.7L 2005-2016
Mazda BT-50/Ford Ranger/WL-C/WE-C 2.5L/3.0L 2006-2011
When replacing cylinder heads, failure to refit all valve lash caps can cause costly engine damage.
Many modern engines, in particular diesel engines have a lash cap fitted on the end of the valve that the rocker arm pushes on.
The lash caps, particularly when coated with diesel engine oil, are hard to see and very easily missed when dismantling the cylinder heads.
The lash caps do not come with a new or exchange cylinder head, unless the head is a fully assembled head with the rockers and/or camshaft already installed.
We have had several instances where a customer has purchased a cylinder head and fitted it without swapping over the lash caps from the original cylinder head with catastrophic results!
A customer had fit a Toyota Hilux 2TR-FE engine with a changeover cylinder head. The vehicle ran fine for 4 months with no obvious noises or rattles. These engines use hydraulic lifters and the lifters will take up the clearance caused by missing lash caps. So there was no apparent rattle or indication that there is any issue.
The engine dropped a valve and the cylinder head was sent back for inspection. When the cylinder head was inspected it was found that the lash caps from the original head had not been fitted by the customer. The valve and rocker on the affected cylinder were severely damaged.
Without the lash caps fitted to the valve tips, it allows the rocker arms to slide off the centre of the valve tips. The rocker arms then push on the valve spring retainer, rather than the centre of the valve stem, which in turn allowed the valve collets to pop out. With the collets gone the valve dropped and broke after hitting the piston.
When dismantling any cylinder head, always check the end of the valve stems to see if there are any lash caps fitted.
In particular, we have seen issues with Toyota 2TR and Ford/Mazda 3.0L WEC engines dropping valves for this reason. As the clearance is taken up by the hydraulic lifter in the 2TR and can be adjusted out when setting the valve clearances on the Ford/Mazda WEC there is usually no apparent indication of the lash caps being missing until the valve drops!
*** Note ***
Valve lash caps are used on an assortment of engines from different manufacturers, so you really need to check each cylinder head to see if these caps are fitted on every vehicle that you remove the valve gear from.