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rover_75
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Discussion Starter #1
Hi everybody
Just wondering about the jiggle valve on the inlet manifold just done the head and I blew it though with a airline from both sides and fitted it back should I of taken it out ? I did remove it on my rover 75 . Anyone any thoughts on this . I’m also going to replace the prt too as mine looks perished inside and the mls gasket blew when the previous owner had it and I want to find out why
 

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'06 MG ZR +120 (HQM) '04 MG ZR 105 (IAB)
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I would not recommend removing the jiggle valve at all - it is there for a purpose.

It is designed to allow gases trapped in the top of the head to vent safely to the expansion tank. Removing it will simply allow coolant to constantly discharge from the head to the expansion tank. As the valve is situated straight above the water pump, that flow will be reducing the volume of freshly cooled coolant flowing through the cylinder head, which is not desirable (there is a lot of evidence that the flow through parts of the head is barely sufficient to start with) - more likely to lead to the sort of localised overheating that causes annealing of the alloy, fire ring indentation and thus another HGF (and if the SLS/elastomer gasket is fitted, overheating degrades the elastomer and leads to it becoming detached from the metal plate which sooner or later leads to oil or coolant getting to where it shouldn't).

Whilst the jiggle valves do occasionally get gummed up, and thus may be seen as creating a risk of trapped gases causing an impediment to flow and lead to head gasket failure, the usual reason for them getting gummed up is either due to emulsified oil in the coolant system from HGF already having happened, or due to lack of proper maintenance - a change of coolant along with a flush at the recommended interval should prevent sufficient build up of detritus that may block the jiggle valve. It also helps to remove the bleed pipe from it occassionally (ie. when servicing) and check it is clean and free to move.

The degradation of the elastomer coating on the cam cover gasket which you showed in another thread (doing-up-a-mg-tf-so-far) is invariably due to significant overheating, and indicates that your engine had suffered significant overheating at the end of the head furthest from the water pump/inlet.
 

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rover_75
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Discussion Starter #3
I would not recommend removing the jiggle valve at all - it is there for a purpose.

It is designed to allow gases trapped in the top of the head to vent safely to the expansion tank. Removing it will simply allow coolant to constantly discharge from the head to the expansion tank. As the valve is situated straight above the water pump, that flow will be reducing the volume of freshly cooled coolant flowing through the cylinder head, which is not desirable (there is a lot of evidence that the flow through parts of the head is barely sufficient to start with) - more likely to lead to the sort of localised overheating that causes annealing of the alloy, fire ring indentation and thus another HGF (and if the SLS/elastomer gasket is fitted, overheating degrades the elastomer and leads to it becoming detached from the metal plate which sooner or later leads to oil or coolant getting to where it shouldn't).

Whilst the jiggle valves do occasionally get gummed up, and thus may be seen as creating a risk of trapped gases causing an impediment to flow and lead to head gasket failure, the usual reason for them getting gummed up is either due to emulsified oil in the coolant system from HGF already having happened, or due to lack of proper maintenance - a change of coolant along with a flush at the recommended interval should prevent sufficient build up of detritus that may block the jiggle valve. It also helps to remove the bleed pipe from it occassionally (ie. when servicing) and check it is clean and free to move.

The degradation of the elastomer coating on the cam cover gasket which you showed in another thread (doing-up-a-mg-tf-so-far) is invariably due to significant overheating, and indicates that your engine had suffered significant overheating at the end of the head furthest from the water pump/inlet.
Hi thank you ,
Glad I didn’t remove it now . On with fitting a new thermostat tomorrow as the old one looks perished and I think this might of added to the failing of the last head gasket
Roger
 
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