Anti airlock nipple on the top of the inlet manifold?

P

paolow

New Member
My poor old P6 has been sick recently but were on the home stretch!

All that remains is to fix the anti airlock mechanism on the top of the inlet manifold that sits between the 2 Su carbs. As i understand it, this nipple has a hose attached that goes into the rad bypassing the stat and it of course allows the air to leave the top of the engine and make sure the whole is always full of water.

Or thats the theory. Ive had my finger in the rad and i couldnt feel water coming into the top of the radiator. i took the hose off and this is clear right through to the rad, Taking the hose off the inlet side of the engine reveals no water issuing from the nipple on that side. Aha! theres the problem!

But then - another problem presents itself! how on earth do I fix this? Ive had a probe into the nipple and it goes in about an inch and a quarter before it hits an obstruction. im reluctant to work too hard against the obstruction in case my probe (a drill bit) goes too far and burts through into somewhere it shouldnt.

What is behind the nipple on the manifold? does the nipple go straight into the waterjacket? is there a 90 degree bend? does the water come up from below somehow? does the nipple come out?

questions questions!

Please help! :)
 
Winding in a suitable size drill bit by hand should shift the crud! The nipple doesn't go into the manifold very far and it go's in straight. You wont damage anything. When it's working properly , with the engine running and with the rad cap off you should see coolant flowing from the pipe into the rad ( opening the throttle by hand helps to increase the flow so that you can see it ).

Roly.
 
ah brill. thanks for that. ill do as suggested and continue as long as brown gunk comes out. if it starts looking shiny and silver i might stop and have a think :)
 
Paolow,
You may have cured the air-lock/obstruction problem within the inlet manifold for some time , by just cleaning out the pipe and a short way into the cast aluminium chamber, however - and I speak from experience having had the same problem a few years ago on my "s"- this small aperture pipe can block again very easily (with me, the drill cure lasted all of a couple of months).
A more long lasting cure -which has lasted years for me - was a thorough clean out of this inlet coolant chamber by removing the core plug on the top and scooping out all the crud inside, it amazed me how much there was in a 60,000 mile engine. Flushed out as much as possible through the open core plug hole. Fit new core plug- you wont get the old one out anything like reusable anyway.

For peace of mind I then used a coolant flush in the system - again a lot of foreign matter came pouring out - before finally refilling with antifreeze mix.

I realise this is not a 5 minute operation but well worth the trouble if a V8 is having overheating/coolant circulation problems.
 
I was trying to get an idea of what you where on about, can't think where this is situated, something I might of checked just in case. Don't worry if it's too much hassle as I say it was only curiosity but it's always nice to have an idea of what part of the motor is being talked about when you're reading the posts. :)
 
Have a look at any underbonnet pcture of a V8 P6 and follow the smallbore hose from the top of the rad to the centre of the manifold between the carbs. It's the metal pipe the hose fits on to that blocks up.
 
With the motor not going and the radiator cap on, disconnect the air hose from the nipple and blow into it. You should get coolant squirting out of the nipple. Dont blow too hard or it will be all over you.
 
having got my inlet manifold off the car at the moment, and reading this thread a while ago, I too noticed a lot of crud blocking the small outlet pipe, and the steel pipe also badly corroded, so I've just drilled out the old pipe and then drilled and tapped a 1/8th BSP pipe thread (there is enough meat to do this) and I will fit a piece of stainless (industrial instrumentation) tube which, OD wise, will take a 1/8th BSP thread on the OD and use this with the advantage of having a slightly bigger ID to help the flow and can be unscrewed for further cleaning if neccessary.

Regards,
 
Scott, Good idea tapping a thread in the casting for a slightly oversized pipe, but be sure that the space within the casting right at the top, is relatively free of crud.
As I said earlier in this thread, I was having blockage problems and eventually resorted to removal of the core plug in the top of the inlet manifold, inside it was caked 1/2" thick with slimey brown stuff ( of course it is potentially the hottest location in the cooling system - when circulation ceases) Good luck with the mod. :)
 

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thanks mike, yes, i still had a bit of crud inside and I'll give it a good cleanout before refitting and looking at your photo I'll have to take some of my mods for posting. and I was thinking of repainting my air cleaner silver as well, there is too much black under there! looks like a nice clean underbonnet you have.

Regards,
 
So what happens about this air lock problem if you do not have this manifold? so therefore do not have the anti airlock nipple?

Does the engine suffer from air locks or is there another way of sorting it?

Just wondered as my car has an offenhauser manifold.
 
Hello Richard,

You don't need to worry about getting air locks with the offenhauser manifold.

The pent roof of the Rover manifold means that air locks will occur, hence the requirement for the bleed pipe.

Ron.
 
Ron /Richard,
Although the offenhauser manifold does not have a pent roof to it – it does have a high point in the "engine cooling system" (higher than the head to manifold coolant ports) and I have often wondered why an air bleed has not been allowed for in the design of this manifold. If, in your experience, air locks are not a problem in practical terms with this manifold, in design terms I wonder why ?
I do know of an +8 Morgan(rover 4.6 engine)owner with an offenhauser inlet manifold who has drilled and freeze shrunk an air bleed pipe into the manifold and P6 like, led the pipe to the rad top, said it cured his circulation problems when engine and cooling system was under stress (racing). Normal road use maybe OK ? :wink:
 
Scott,
Thanks for the compliment regarding my car underbonnet cleanliness, but I have to own up :oops: , that it is fairly freshly done, as I had to have the engine out this last June/July (coincidentally to thread - to cure a coolant circulation problem in the block thankfully now fully resolved 1000 miles later I feel I can say this ! :LOL: )
Bring on some photos of your mods, would be most interesting to self, and members, I am sure.
 
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