P gasket problems.... (?)

Disco1BFG · Jan 18, 2016

So, whilst de EDCing my 300 about a year ago, I fitted all new gaskets and seals to all the bits I either had to disturb, or could get at without a load more work. This included the P gasket. I used a genuine one, and long story short, in less than 5K miles, it has failed.

On inspection, the middle bolt through the water pump and P gasket, was loose (!) - the other two were still at torque, which is good, as they were all torqued up, and thread locked with loctite 242.

Clearly, I am going to replace it, and use new bolts this time, but I would be grateful of sensible opinions as to what has gone wrong please...

TIA

Kwakerman · Jan 18, 2016

Did you use a metal or fibre gasket? For a bolt to lose torque one of these would have taken place:
1. Not tightened to correct torque on assembly.
2. Gasket has compressed over time.
3. Bolt has stretched.
4. Someone has loosened it.
5. High levels of vibration on that bolt.
6. Something trapped under bolt head on installation.

3, 4, 5 and 6 are highly unlikely, 2 is unlikely if you have used metal gasket and correct torque should also compensate for any gasket compression. Unfortunately that leaves us with option 1 especially as you thread locked it as that should stop any rotation. I've never used threadlock on those bolts as it isn't needed and you may cause yourself issues in the future, I do however use new bolts all round each time (only a couple of £'s)

Disco1BFG · Jan 18, 2016

Kwakerman said:
Did you use a metal or fibre gasket? For a bolt to lose torque one of these would have taken place:
1. Not tightened to correct torque on assembly.
2. Gasket has compressed over time.
3. Bolt has stretched.
4. Someone has loosened it.
5. High levels of vibration on that bolt.
6. Something trapped under bolt head on installation.

3, 4, 5 and 6 are highly unlikely, 2 is unlikely if you have used metal gasket and correct torque should also compensate for any gasket compression. Unfortunately that leaves us with option 1 especially as you thread locked it as that should stop any rotation. I've never used threadlock on those bolts as it isn't needed and you may cause yourself issues in the future, I do however use new bolts all round each time (only a couple of £'s)

Thanks for the reply. Exactly the detail I was after.

Gasket was a genuine LR, tin gasket.

My "best guess" is number 3 - and I will use new bolts "this" time (!). As you say, they are next to nowt - about £8 off the bay for both gaskets and all new bolts = borderline irrelevant.

I would agree that the others are all possibilities. Even option 1 is a possibility, as no one, not even me, is perfect! Option 4 is the most unlikely - cos no one but yours truly, goes under the bonnet!!

Now, re thread lock, I use loctite 242 quite a bit, as it is fairly gentle - and I always clean threads with a tap or die, and degrease before using it... but I do take your point.

ATB

Kwakerman · Jan 18, 2016

Bolt stretch is unlikely unless the original was either very corroded or had been over torqued in the past (to beyond its yield point) as it isn't that high a torque on them.

P gasket problems.... (?)

Disco1BFG

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Kwakerman

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Disco1BFG

Well-Known Member

Kwakerman

Well-Known Member

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