Hi all,
I was hoping for some advice on the following possible? issue.
I have taken the cylinder head off a 2001 Rover 25 (K-Series Engine after I carried out a compression test and found widely differing results between all cylinders.
I checked to see if the head was warped using a straight edge and feeler guages, I found no evidence of any warping.
What I did find however were strange circular undercuts running around two-thirds of the circumference of each cylinder combustion chamber.
The undercuts are about 1 mm thick and .0006" deep. My findings are quite hard to explain but if anyone thinks they can help, I can sent a very clear digital photo of the undercuts via e-mail.
There is no undercutting towards the inlet side of the cylinder head.
I have changed many head gaskets and have never seen anything like this.
As I have never changed a K-series head can anyone tell me if this is undercutting is:
1)Supposed to be there
2)Should be skimmed out
Any help would be greatly appreciated
Thanks,
Stephen
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If the undercuts are really only 0.6 thou deep, this could be caused by firing ring fretting, where the reinforced edge of the bore hole in the gasket vibrates. It is much worsened by pre-ignition, but knowing the design history of this engine, it's probably due to poor force distribution following thermal cycling. Skim it out and sell whatever goes around this truly dreadful engine - sorry.
Good job they never tried making it into a diesel!
659.
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Oil and plate glass are a better "home made" way of assessing head flatness. Pinch the top off an old photocopier (A3) - this works really well.
659.
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I'm with 659FBE on this one and the warping of these heads is fore and aft across the width, I think you will find the head is slightly concave, a gentle skim, a good finish and new bolts into clean threads in the block should breathe some life back into her. Regards Peter
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like the glass idea 659FBE and also agree with the sell, sell, sell, idea.
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Thanks for your responses,
I must apologise I should have written that the depth of the undercut was .006 (0.15mm) rather than .0006.
659FBE: The fretting explanation you described really does add up, I looked into it a bit more on the internet after reading your advice.- Thanks
Can I take it then that like every other engine I have worked on, the K-series should have a completely flat surface with no marks or indentations - I just didn't want to skim the head to find that the undercuts were actually meant to be there for some strange reason.
Many thanks,
Stephen
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Hi Stephen,
All the answers you have been given so far are correct. The rings you see are caused by the head gasket fire rings becoming loose and 'chattering against the head. It does not affect the block as they have liners which are much harder than the fire rings. If the car is sound, fairly new, low mileage and is reliable then its worth doing. Get the head skimmed, fit a new gasket and bolts (get them from your local Partco - much cheaper)and you should have no further problems.
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These are the views of Robin the Technician with 35 years in the trade. I fix, therefore I am...
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Thanks to all who helped me out with this issue.
Have a Happy New Year.
Stephen
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