Zero compression on No.4, blowing brake servo off and rough!

Post by **Doodleboink** » 25 Sep 2007, 14:25

Ok. Just moved house and had the camper stuffed full of a few bits and peices that wouldn't fit in the Luton. Hereford to new house was approx 150 miles and she didn't miss a beat. Got to new house and parked up, unloaded then later started up to go get some scooby snacks. Sounded really really bad. Really tapping and initially led me to think No.2's rocker had worked loose again and the pushrod was hitting the rocker cover. Nope. Nothing wrong that side. Checked other side, nothing visually, but noticed that there was clearance on No.4's inside rocker (is that exhaust or inlet???) Carried on driving and noticed popping from engine, then had to emergency brake due to old person in car in front and reallised we'd lost brake assistance. Stopped by standing on the damned peddle but knew something was definately wrong. Compression test is 120 all round bar this pot, which failed to register owt at all! Is it possible a valve has stuck open? What can I do? Would it hit the piston if it stuck open? Or are these non-interference? I'm prepared for taking the head off bar the fact I can't find valves on JK's, only rebuilt heads.

Any magic potion that'll do it?

(Searched for a bit, then it went belly up and into debug mode.)

TIA!!!!

Post by **toomanytoys** » 25 Sep 2007, 14:37

Mmmm... sounds like it may have dropped a valve seat..

Post by **Doodleboink** » 25 Sep 2007, 14:57

toomanytoys wrote:Mmmm... sounds like it may have dropped a valve seat..

Yeah, that sounds feasible. What's involved? New valves? Obviously valve seat, headgasket, pushrod seals. What else? I'm figuring seized exhaust studs, tho one is out already without too much agro.

Post by **Doodleboink** » 25 Sep 2007, 18:59

For the non-pyschics, she's an '82 2l AC.

Post by **horizontal kipper** » 27 Sep 2007, 08:28

I had this same problem a while back if this link dont work then check my early posts. good luck. http://archive.club8090.co.uk/viewtopic ... c&start=15

Post by **Doodleboink** » 27 Sep 2007, 09:50

Head's off and it wasn't pretty at all. New head time. Dropped a seat alright and chewed up the surrounding metal a treat. Damaged the piston face slightly, tho it should be ok. What depth is the metal on the face of a piston?

Post by **toomanytoys** » 27 Sep 2007, 11:14

Be carefull with the piston... if its been really well smacked it may be cracked or will crack under a lot of heat...

if it is just badly marked, then paper off the rough bits... you dont want any sharp buts as these can cause hot spots and detonation.

Post by **Doodleboink** » 29 Sep 2007, 10:32

Ok thanks for the advice. I'll take a closer look at some point and decide what to do about it. It looks superficial, but then, what do I know.