P Gasket leaking again which gasket goo to use?

**Coastie** · 11th March 2006, 10:40 AM

This is the fourth gasket to leak at the P gasket on my 300Tdi. I've used two paper gasket and now two metal ones and whilst the time interval favours the metal gaskets for longevity between leaks I'm getting annoyed at doing it every couple of years.

I've used different gasket cements as well and was wondering if a more flexible silicon based one would improve the situation. The ones I've used seemed to go hard with the heat. I assume the iron engine block heats and cools at a different rate to the alloy housing and this causing the joint face to expand and contract. The leak only seems to occur during the cooling phase and of course is intermittant sometimes weeks apart. There is no evidence of a leak for weeks and then there is a small patch of coolant beneath the front of the block. Coolant level hardly ever changes though, about 250ml is all I need to add.

I've seen other threads about the rusted bolts due to the leaking at the P gasket. Is there a definitive way to stop this.

**incisor** · 11th March 2006, 11:27 AM

most silicon based sealants can only handle 18psi at best.

i use stag on anything relating to coolant and touch wood, never experience a problem.

**p38arover** · 11th March 2006, 01:08 PM

What's a P gasket?

Ron

**Coastie** · 11th March 2006, 02:04 PM

Behind the water pump or adjacent to it on the 300Tdi is a housing from the engine block to the water pump. There is a gasket there that is shaped like a P thus the name.

Langy or someone had a post on here with photos about the rusted bolts due to a leak. Can't find the post at the moment.

Found it
http://www.aulro.com/modules.php?name=Foru...=asc&highlight=

**one_iota** · 11th March 2006, 02:11 PM

Langy's post on the subject:

http://www.aulro.com/modules.php?name=Foru...iewtopic&t=7456

disco95 · 11th March 2006, 04:07 PM

Red ATV silicon should do the trick. I bought it for the jet ski, water flows through the same housing as the exhaust, no gasket at all in the joins. ATV works a treat. Even used it in conjunction with the slightly worn metal thermostat gasket. Can handle a goodly amount of heat and pressure just can't be used for head gaskets as it breaks down with fuel and such.

**langy** · 11th March 2006, 06:18 PM

Yep, I use red RTV, including on the thread themselves. Note, however, that it may not be just the p-gasket this time. I put in a new water pump with a paper gasket when I did some work around the alt, and for some unknown reason the bottom of that gasket, at the front of the P section, failed. Looked just like a failed p gasket. I tightened the bolts up a little, and then the water pump developed a crack ( My fault ). So I went back to my spare, and no gasket but only Red RTV. Might try blue or copper RTV next time, Red seems to not to gel suficiently.

Langy

disco95 · 12th March 2006, 10:48 AM

Oops, must check that I could've sworn it was ATV.

ops:

**DEFENDERZOOK** · 12th March 2006, 09:45 PM

<span style="color:blue">for all cooling system components i use hylomar.....
never had a problem......</span>

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