After some cooling system problems, my car has been diagnosed with a porus head, the car, a 525i is 14 years old, with 196k on the clock.

I've been recomended to have an exchange from head technology, or something similar in northants, £460 with a three year warranty, and they will allow my chap in worcester to be their agent for the warranty should it be required.

Apparantly the recon head is a complete rebuild, valves cam etc, but not the hydraulic followers, whatever they are.

I have been told its just general wear and tear, a lot of miles, and corosion over the years by antifreeze.

Do any of you have any experiences like this?

The hydraulic followers are small assemblies that rest on the cam and take the motion from the cam to each of the valves.  The're hydraulic because they "pump up" with oil and should keep a constant valve clearance (assuming the oil is ok and they themselves aren't knackeded)  The older method by overhead valve or pushrods, is to use mechanical force, which meant that a mechanic should check each clearance every so many thousand miles.

So, hydralics are probably better and cheaper for servicing.  Don't know of their reliability in bmws or their replacement cost

The below link will take you to the Honest John web site:

http://www.honestjohn.co.uk/index.php?url=/carbycar/index.htm">http://www.honestjohn.co.uk/index.php?url=/carbycar/index.htm

This details pros / cons of the e34.  I've also copy/pasted the relevant para which does indicate this problem is known (my highlighting)

What to Watch Out For

Electronically 'corrected' odometer/on-board computer (clockers sometimes steal one of the chips). Make sure dash display all functioning, as new preinted circuit costs £400. Accident damage. Electric window problems. Faked service indicator. Whining manual gearbox can last for years but expensive to fix. Slurry autoboxes with neglected ATF and filter changes. Accident damage to M5s. Earlier model, less powerful, imported LHD M5s. Smoke from worn valve stem seals. Overheating from cracked cylinder heads on older 6-cylinder 12 valve engines. Cylinder head studs of 12 valve engines can shear. 'Problem' M60 V8s. Duff catalytic converters. Smoking 1.8s (valve stem seals). Noisy 12-valve sixes. Misfires from faulty integrated coil units on later 24v. Rear subframe rubbers (MOT failure point - £200 to put right). Damage to front suspension and steering (look for uneven tyre wear). Duff ABS. Service light indicator can easily be re-set, so a paid invoice is the only guarantee of a recent service. Check tool kit is all there.

No doubt others will know more than I, ref the heads, what of the alan cowland team you mentioned to me?  May cost less.

rgds

Good luck, the warranty does give peace of mind

rgds