Thread: Plastic dowels and Head gasket problems

Originally Posted by alien d2

Ummm....,
Is this diameter or length or both?
I've got steel ones I was going to put into a 2/99 motor.

Thanks for your timely advice,
Cheers Kyle.

Kyle,

I am not sure what the issue is, as when I first heard of this I immediately compared the plastic ones to steel ones, and they are identical. I have since fitted many to early Td5's (99, 2000 etc etc) and as yet have had zero problems. I will continue to do so.

There must've been a reason for LR engineers to say this, but I can't see why it is so if the plastic and steel dowels are of identical dimensions.

JC

had a thought about this today. 2 common problems with the TD5 the plastic dowels letting go, and the cast exhaust cracking. i was wondering if there could be a link. The dowels should not cause a head gasket problem. but could fail due to other problems, i.e. the head moving due to overheating etc. or possibly the head moving due to a cast exhaust manifold warping and putting pressure on the head due to dissimilar metals expanding at different rates.? seems like a possibilty. i had a strange problem with my TD5 dropping colant, but i never overheated. ended up being a crack in the head between the fuel rail and the water gallery and was slowly pumping the coolant system with deisel and occasionally overflowing the expansion tank, but she never overheated. when i took the head off the dowels were both broken, head studs were all nice and tight, but manifold had a warp.

Originally Posted by justinc

Kyle,

I am not sure what the issue is, as when I first heard of this I immediately compared the plastic ones to steel ones, and they are identical. I have since fitted many to early Td5's (99, 2000 etc etc) and as yet have had zero problems. I will continue to do so.

There must've been a reason for LR engineers to say this, but I can't see why it is so if the plastic and steel dowels are of identical dimensions.

JC

Thanks JC,
I compaired mine and they looked identical so It was best to asked.
Just for the record, 1 usual movement, 1 broken um .


Rosscoe68,
You might be on to something there.

Cheers Kyle.

Originally Posted by alien d2

Thanks JC,
I compaired mine and they looked identical so It was best to asked.
Just for the record, 1 usual movement, 1 broken um .


Rosscoe68,
You might be on to something there.

Cheers Kyle.

Just another bit of info, If anyone is worried about the linear expansion of the steel dowels, then don't as there is plenty of room in the head for them to grow longer when hot. That was what I thought they meant by not replacing the plastic with steel, but again I couldn't find any good reason why not.

JC

Thought i'd meashure the lengths before I fitted my dowels.

Plastic dowel as removed 19mm. (Distorted on removal).

Britpart part no. GI 103450 corresponding to YLL,500040. ...18.55mm.

Hole in block......... 9.4mm (shortest hole)
Hole in head.......... 8.7mm (shortest hole)Nb. 0.13mm removed on surface grind prior to meashuring.
= 18.1mm plus head gasget.

Head gasget 3 hole to suit 0.571-0.650mm piston protrusion
.........@0.65mm(3 hole ie. thickest available)

This gives me 18.75mm of hole for 18.55mm of dowel
Plus the holes are tappered which I didn't meashure and the dowels are shamfered too.

Cheers.