i have a rover 400 series car which is 5year old and the cylinder head has blown and when i rang a garage to see if i could book it in they would not take me on saying they have 4 cars( rovers ) already in waiting to do .
at the time my car went two other people that i work for said that they had the same problem with their rovers .
is it a design fault with the k series engine and if it is can we get compansation for the work that has been done on the car.
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John - I'm no expert, but I've heard that the only head problems with the K-series is caused by poor mainenance, especially failure to keep the coolant level up.
I've had two 200-series Rovers (a 1.6 and a 1.8), always had them serviced properly and never suffered probs at all.
Perhaps someone with more knowledge will shed some light...?
Regards
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A question was asked recently by a chap interested in buying a 214(new shape) - but it was never really answered - he asked about the bit in HJ's car by car breakdown that states these engines need regular tightening of the head bolts - someone else said this is NOT the case but I believe it is - why else do so many K series units suffer head faliure?
Perhaps the great HJ can answer this once and for all - AND tell us how often the bolts need tightening!? please
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"but it was never really answered"
I think it was!
If Mr A Moorey says they shouldn't be tightened then that is the answer. QED.
Perhaps HJ means that if you ever remove a K Series head it should be overtorqued when you pop it back on?
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Thats not what the local rover dealer says... they say should be re-torqued every service
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Cylinder head bolts?
Interesting. It's not in the service shedule on mine.
I wonder if they suffer head failures *because* they are tightened.
I will wait for Mr D Lacey or Mr A Mooreys view on this but if it's in the service schedule I guess it must be done.
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As HJ states 'To prevent cylinder head warping and cylinder head gasket failure, all K Series engines need their head to sump stretch bolts re-torquing periodically' Its these Stretch bolts the guys are talkign about, Dave.
No, they are not listed in the service guide, but then thats often the case with guides - things are 'discovered' after the guide is produced. My local Rover dealer (one of the oldest in the country) says they DO need re-torquing and they tend to check/do them every time one comes in, otherwise they suffer many problems least of which includes visible weeping...
Hope this all helps!
Perhaps HJ can give us some indication of when he thinks they should be done?
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So this whole discussion could be summarised with the sentence:
"The Rover Service Schedule does not recomend you touch the cylinder head bolts."
I can also see why Rovers have a reputation for head gasket problems if dealers all over the place are shearing head bolts as fast as their clumsy hands can!
I'll defer to DL & AM on this but if Rover don't think it should be done and the guys who know on this site don't reckon it should be done then as far as I'm concerned it's a bad idea.
Interesting topic though!
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..sorry I didn't mean that to sound as rude as it did!!!!
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I'd agree with Andrew Moorey. From an engineering aspect, I don't believe stretch bolts should be retorqued. Stretch bolts are just that. You tighten them on installation, and they are tightened to a level which puts the material into the plastic zone. That is, if you loosen them, they won't go back to their original length. It assures that the bolt loading is achieved. Usually you do this not with a torque wrench, but by tightenig a specified angle on the bolts after reaching a certain torque. The problem with retightening is that they will stretch even more, and this won't increase the loading on the engine joints, infact it may even reduce as the material approaches failure. Check a typical load/extension curve from College days. Keep tweaking up the bolts and they will snap.
Thye are not usually used more than once - they need replacement after use.
Regards
John
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Hmm interesting....
The K series engine through bolts (almost 50cm long!) are indeed angle torqued 90deg then 90deg again after an initial 25nM torque loading. This provides more than enough clamping force to achieve a durable seal. Never have I seen any reference to re-torquing the bolts at service time.....as John rightly says, they should never be touched after final tightening.
The K Series through bolts can actually be reused as many times as needed, aslong as a measured section of the bolt is within a certain tolerance. To this point, we have never had to replace a set of bolts....yet!
K series head gasket failure is relatively common because of the low coolant capacity of the engine block (1.5 litres!) As soon as there is a small leak, the system runs on reduced coolant capacity and bang goes the weak link (thats what a head gasket is, a fusible link, really)
Inlet manifold gasket leakage (of coolant) is a favourite weak point which will lead to HG failure, if left unchecked
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So, I dont dispute this - but where does HJ get his line from? It must have some truth if he and dealers have heard it?
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Dave
Looks like these bolts are made with just a section which is re-heat treated to give a ductile section. Normally it's not recommended to reuse stretch bolts, but presumably because of the length, it's been possible to include a longer 'stretch' section than usual, hence keeping total strain within acceptable limits even after more than one use.
They will need to be replaced at a specified length because by then the ductile section will be on the point of the load/extension curve 'dropping' - failure point is approaching and bolt load will be decreasing, so the required clamping load will not be achieved.
regards
john
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Many thanks to Dr Dave. Car by car entries have now been corrected.
HJ
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Trouble is you have got me a bit worried now. Dr Daves comments are a crumb of comfort. Indeed many of the K series engines I get called out to are suffering from low coolant, usually from the radiators which fall apart as soon as you look at them and the difficulty in bleeding the air out of the system if you dont clear out the little tube adjacent to the inlet manifold. Perhaps the line from MG-Rover is that a torque wrench should be applied at a specific setting to check that none of the head bolts have 'let go' to that extent. In my experience in the many head jobs I have done on K series I have never found a 'loose' headbolt.
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Andrew
Yes, all a check like this could achieve is to ensure a bolt had not let go significantly. The thing with stretch bolts, unlike normal 'elastic' bolts, is that a torque wrench doesn't give the correct bolt load. It's used to give an initial 'nip' of the joint, but then the bolt is tightened a specified angle, and the bolt itself yields. The yield point is set by clever material choice and heat treatment, to give a precise load. This cannot be checked again without completely loosening the bolt and following the tightening sequence which (a) shouldn't be necessary (as you've found), (b) would be a bad idea for gasket sealing (c) can't be repeated indefinitely or the bolt will fail.
Regards
john
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Terry said>
"Thats not what the local rover dealer says... they say should be re-torqued every service"
If that is what your dealer is saying, I suggest you change your dealer pdq!
NEVER tighten the through bolts any more than the initial 20Nm +180deg+180deg
.........UNLESS you want to pull the engine apart to replace the lower bearing ladder due to a stripped thread..........
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Call me immature but I think it's time for me to sing the I was right song!!!
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I'm glad to hear the confirmation but never have/would re-torque these bolts.
It isn't possible to re-torque or "nip-up" these bolts as they are tightened by an "angle torque" figure. The whole point of this is to apply a set stretch to the bolts that isn't accurately produced if done by a torque figure alone. ie. the is no torque figure to re-torque them to anyway.
David
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Perhaps Terry M should name and shame the Rover dealer who habitualy re-torques his customers cylinder head bolts.
One for the bad garages section?
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