Hi All,

First post so please bear with me!

Have just bought an R52 convertible W10 engine with 112,000 miles. Purchased very cheap and first time out on a short drive it overheated with fluid coming from the thermostat housing. Replaced that, bled the system, ran ok with heat from the heater for a short while and then overheated again. Symptoms being similar to an airlock, no heat from the heater and bubbling in the expansion bottle. Accompanied by smelly white smoke from the exhaust. Other symptoms since the 1st overheating are poor starting and idle which can rise and fall by a couple of ,000 rpm.

Quick gas test confirmed suspicion that the head is either cracked or the gasket has gone. Either way, the head is coming off. Did a compression test expecting to find 1 or 2 cylinders below spec but all 4 are reading between 125 - 135 psi which according to the Haynes manual is well under spec. Am I right in suspecting these readings indicate the valve timing being out with the chain possibly jumped a tooth?

Any thoughts appreciated.

 

There's a lot of variables that can effect measurements (gauge accuracy, was the throttle open/closed, battery strength/cranking speed, etc.).
I've also found that compression tests are not a good indicator of a blown head gasket. So take your reading with a grain of salt.

 

Sorry - should've said that the battery is in good health (and was supported by a charging pack when taking the compression tests), tests were done at full throttle and the engine was warm.

The head gasket diagnosis is based on a gas colour test from the expansion bottle.

 

At 112K miles probably a good idea to just renew the cam chain, sprockets, guides/tensioner, valve stem seals, maybe more like a full engine refresh. New pistons/rings, valve job, main/rod bearings, the full enchilada. Whatever you decide to do when you put the engine back together you will of course ensure cam timing is correct.

 

Its about a 4-6 hour job. Straightforward and not really challenging. Take your time. Purchase a quality MLS Gasket.

 

If you haven't disassembled it, do a leak down test on it if you want to get a more detailed look at the health of your engine.