Has anyone fitted a new head gasket and used a product such as 'Hylomar Blue' (high performance, non-setting gasket and jointing compound) on either an MLS or Elastomer gasket to help seal between the HG and the block & the head itself? Views appreciated.....

If both block and head are flat you shouldn't need sealer.

Most head gaskets have all the seals they need made into them both silicone and metal press.

You can't use Hylomar on the MLS gasket, as it's already coated in a thermosetting adhesive.

In theory you could use a smear of Hylomar on the Elastomer gasket, but it shouldn't be needed if the surfaces are within specification.

Nodge68 said:

You can't use Hylomar on the MLS gasket, as it's already coated in a thermosetting adhesive.

In theory you could use a smear of Hylomar on the Elastomer gasket, but it shouldn't be needed if the surfaces are within specification.

Click to expand...

Thanks

+1 on the "no need for hylomar"
Two things you need to check when replacing a head gasket:
1. The hardness of the cylinder head
2. The heights of the cylinder liners from the block face.

Not many people have hardness testers, but a good way to tell whether your cylinder head is able to go again is to inspect the area around the combustion chamber. There should be no more than the faintest, thin line encircling part of the combustion area of the head. If it is fully circumferential, wide and deep (deep enough that the ridge catches your finger nail), the chances are that the cylinder head alloy has gone soft. No head gasket will satisfactorily seal for any prolonged period of time. It will fail again. You'll either need to replace with a good cylinder head or get the head repaired (there are a few options available to do this if necessary).

The cylinder liners should be a couple of thou of an inch proud of the block face. If, as is common in my experience, the liners are effectively flush with the block face, don't fit an MLS, as the fire rings will not adequately seal. Use a decent Elastomeric gasket from a reputable source (I've used Payen). If there is adequate stand-pround, then arguably, the MLS is the optimal option, but I've had many thousands of reliable miles with elastomeric gaskets, so I would not write that option off.

Good luck!