The July edition of Car Mechanics magazine contained a 'Star' letter, relating to the K series head gasket failure problems, by a chap called Mike Humble. As the 1.8 75s & MGZTs are the most maligned in the R40 range and can often be bought for peanuts, I thought it worth relating his comments on here.
He states that alloy sumps were first introduced on the MGF, and MGR changed the cylinder block design to an 'open deck' type to accommodate the new liners for the larger 1.8 versions. This compromised block strength and resistance to flex under high torque loadings. This allowed the the head to 'shuffle'; the nylon dowels were also compromised and the silicone sealing beads were wiped out.
The excellent 'through head' bolt design was also compromised. The bolts end up threading into an oil ladder at the bottom of the internal block casting. By fitting a modified ladder, the flexing problem is dramatically reduced; it is made of aviation high tensile LM aluminium, which is over 25% more rigid under all engine temperatures.
The above modifications are currently used on the MGF and MG6, and has eliminated HGF (Head Gasket Failure). The parts are available from X-part and only adds about one hour to the job. Providing all the other checks are made, such as liner protrusion, head surface condition, cooling system, etc., it is a fit and forget modification.
He warns about avoiding cut-price options of uprated head sets, many from Asia. Go to a specialist who will fit the 'full' conversion.
I think this letter put the situation in a very concise way. Basically, do the full conversion and pay the higher price and you will be unlikely to ever have the problem again. The 1.8s scare people; yes there was an inherent design fault, but the problem is perpetuated by not doing the remedial work properly, this results in the owner experiencing ongoing problems.
Roverite.
He states that alloy sumps were first introduced on the MGF, and MGR changed the cylinder block design to an 'open deck' type to accommodate the new liners for the larger 1.8 versions. This compromised block strength and resistance to flex under high torque loadings. This allowed the the head to 'shuffle'; the nylon dowels were also compromised and the silicone sealing beads were wiped out.
The excellent 'through head' bolt design was also compromised. The bolts end up threading into an oil ladder at the bottom of the internal block casting. By fitting a modified ladder, the flexing problem is dramatically reduced; it is made of aviation high tensile LM aluminium, which is over 25% more rigid under all engine temperatures.
The above modifications are currently used on the MGF and MG6, and has eliminated HGF (Head Gasket Failure). The parts are available from X-part and only adds about one hour to the job. Providing all the other checks are made, such as liner protrusion, head surface condition, cooling system, etc., it is a fit and forget modification.
He warns about avoiding cut-price options of uprated head sets, many from Asia. Go to a specialist who will fit the 'full' conversion.
I think this letter put the situation in a very concise way. Basically, do the full conversion and pay the higher price and you will be unlikely to ever have the problem again. The 1.8s scare people; yes there was an inherent design fault, but the problem is perpetuated by not doing the remedial work properly, this results in the owner experiencing ongoing problems.
Roverite.
