Technical Rocker Leak

[FR85]

Hi All,

Have a leak/mist coming from the rocker gasket, sourced a new composite gasket, used Loctite gasket sealent on the cover side and grease on the head side but it's still there. Engine has a bit of blowby, am going to remove and clean the backfire device and see if that reduces some pressure. Rebuild at the moment I do t think is an option financially.

What are people's views on composite/cork or indeed silicone gaskets for this application?

Have put two covers on a sheet of glass and both are high on the straight/thermostat side, can get the smallest feeler gauge in there but I don't think there were ever 100%.

Thanks all!

Gav

 

[Bleeding Knuckles]

Hi All,

Have a leak/mist coming from the rocker gasket, sourced a new composite gasket, used Loctite gasket sealent on the cover side and grease on the head side but it's still there. Engine has a bit of blowby, am going to remove and clean the backfire device and see if that reduces some pressure. Rebuild at the moment I do t think is an option financially.

What are people's views on composite/cork or indeed silicone gaskets for this application?

Have put two covers on a sheet of glass and both are high on the straight/thermostat side, can get the smallest feeler gauge in there but I don't think there were ever 100%.

Thanks all!

Gav

Hi Gav, you will find many differing opinions on the rocker gasket, I have used both and both have worked well. But first you must be sure that both the head and the rocker box contact areas are spotless!!!! I clean both with methylated spirit (not white spirit) to ensure a clean join. Fitting the gasket - if cork or rubber - is simple, gasket onto the head (NO sealant) and then the box (NO sealant) torque down the two nuts SLOWLY allowing the gasket to settle each time. You will have to gauge when the tightest setting is reached, but don't overdo it and squeeze the gasket out of the join. Providing the box to head join is not too different they will seal. If the join is not good you will probably have a box that has been overtightened at some point and will need to 'adjust' it or replace it !! You say you have blowby - what evidence do you have of this ???? The flame trap should not be a cause of over-pressure in the rocker box area but check the area is not blocked anywhere .
Ian.

 

[FR85]

Ian,
Thanks for the quick reply!
Both surfaces were spotless, opted for the petrol on a rag approach but they were clean. Did valve gapping while in there also I may add.

Will try cork and see how I get on as the composite I feel doesn't allow for much squishing if you get me...

Blowby, when you pull the oil cap she's fairly panting for want of a word....normal maybe?

I was just going to pull the flame trap and clean it just in the event it's clogged and causing excessive rocker case pressure.

 

[the hobbler]

Personally, I always use the 'rubberoid' gasket for the rocker-cover and NO sealant. Something to check---make sure that the rocker-cover isn't sitting on the top edge of the thermostat housing. If the thermostat is as far over to the right (looking from the rear) as it can go, and the thermostat housing is a bit high, the gasket won't be compressed to the point that it will seal. If this is the situation, carefully file down the top edge of the thermostat housing, and put plenty of cloth round where you are going to file to ensure that no filings go into the engine.

 

[FR85]

I was out doing a bit of head scratching tonight, I'm having problems with the clutch in my 850 Berlina now too! :bang:

Looked at what you suggested and it all seems flush with no rises on the stats tinwork. The gasket is still as was assembled and it looks 100% flush, when I strip it I'll check it with a straight edge and see if theres a rise but to the naked eye it seems legit.

I'm going to see how I get on with clutch adjustment and see what I may need to order for that in the next day or two and order both cork and silicon gaskets on the one order.

These things can be painful!

 

[the hobbler]

It is not the way the gasket sits, it is where the rocker cover sits that can cause the problem. Make sure that when you fit the rocker cover in place, it is not actually sitting down on the top lip of the thermostat housing when you tighten the rocker cover nuts.

 

[FR85]

Thanks Hobbler, it seems to be sitting all nice nice, will take a pic later and load it up so it can be seen. Later today I think will be an all Fiat day in the garage!

 

[fiat500]

In addition to supporting all previous advice, before starting and during tightening, I would check very carefully that the rubberoid gasket is properly aligned so that the bead which is pressed into the flange of the rocker cover is centralised onto the gasket all the way round.

It's very easy for the gasket to bow in or outwards of the correct location. To this end I would consider using a very sparing amount of a gasket compound to locate the gasket exactly on the surface of the head.

It can be a bit of a faff to fit the cover past the tight area near the carb and that is when the gasket will most likely get dislodged.

That bead on the cover is what can eventually cut through the gasket if you overtighten. It's better to undertighten at first and then nip it up a bit more if there is a leak on running. I also re-check after a few days to see if the nylocs are loose. That takes some judgement as they should never actually be as tight as they potentially could be. Use new nylocs each time because otherwise, the main thing securing the nuts is the upwards pressure exerted by the gasket.

By the time I'm 100% certain that I have no leak, it's usually time to check the tappet cleaances again.:bang:

 

[FR85]

In addition to supporting all previous advice, before starting and during tightening, I would check very carefully that the rubberoid gasket is properly aligned so that the bead which is pressed into the flange of the rocker cover is centralised onto the gasket all the way round.

It's very easy for the gasket to bow in or outwards of the correct location. To this end I would consider using a very sparing amount of a gasket compound to locate the gasket exactly on the surface of the head.

It can be a bit of a faff to fit the cover past the tight area near the carb and that is when the gasket will most likely get dislodged.

That bead on the cover is what can eventually cut through the gasket if you overtighten. It's better to undertighten at first and then nip it up a bit more if there is a leak on running. I also re-check after a few days to see if the nylocs are loose. That takes some judgement as they should never actually be as tight as they potentially could be. Use new nylocs each time because otherwise, the main thing securing the nuts is the upwards pressure exerted by the gasket.

By the time I'm 100% certain that I have no leak, it's usually time to check the tappet cleaances again.:bang:

When moving the 500 out today to make room to get the 850 up on the ramp I gave the nuts another nip and checked it for oil because I was going to leave it run for a bit to charge and warm up and I don't like to speak too soon but I think that final pinch may have done it, ran for about 15 mins at high idle and no oil present.

Touching wood of course but hopefully it's clinched it. Very hard to gauge when your crimping them down.

 

[FR85]

Evening All,

Brought the 500 for an energetic run this evening and all seems to be well on the rocker leak front, far too hot to put the hand in and feel about but there wasn't the splashy mess I had become accustomed to!

I also managed to modify and fix the clutch on the 850 so I'm a happy camper in that I'm back to firing on all 6 cylinders!

Thanks all, stay safe!

Gav