Off a cylinder, help please

Post Wed Nov 28, 2012 10:53 am

a while ago i purchased a tech II 325 sport advert said head gasket problems. So picked up the car took it home, tried to get her fired up which was unsuccessful. car had lay in a garage for ten years, fuel had all evaporated i guess from not having the correct filler cap on and the inside of the fuel tank was in really bad condition, so i purchased a good tank and fuel pump, fresh fuel and bang she fired up.

so after lettiing the car tickover for a while give her a rev and i could hear her misssing. the car doesnt seem to be overheating, no oil in the water or anything.

done a compression test and one pot is down. my mates a mechanic but has limited time to spare. so i was thinking of taking the head off myself to investigate.

any advice would be appreciated, and is the head that difficult to take off as im not a mechanic butr god loves a tryer!

Post Wed Nov 28, 2012 11:13 am

Reads like a sticky valve.

Have tried removing the rocker cover and running the engine to make sure the valve gear is working on the weak cylinder?

Take great care,if the engine has been stood for ten years the cam belt WILL be suspect,do not rev the engine!

M20 is a lovely engine to play with,comes apart in a logical and sensible way.No reason why you cannot remove and strip the head at home,expect a parts/machining bill in the order of £300 as a minimum,these jobs do tend to suffer from the 'whilst I have it in bits' syndrome!

You do not need any 'special' tools for the job,torx female socket for the head bolts,valve spring compressor if you are going to remove the valves yourself,everything else is quite straightforward.

Have rumble through the zone wiki,sure there is a photo guide there.

Post Thu Nov 29, 2012 1:50 pm

Thanks i will take the rocker cover off and have a look, and hope that is the problem. then a bit of welding to inner rear arch were the vapour tank is and also battery tray, apart from that cars in pretty good order. Going to take the kit off and see is it hiding any rust as i want to get the wagon a full respray. When rocker cover is off I will be looking for a stationary valve (not moving)? i put a new cam belt on before i started it for the first time and by the looks off the belt i was lucky to do so, there was more cracks on the belt than a bus full off women!

Post Thu Nov 29, 2012 2:02 pm

There may be a valve stuck open,I guess that the clue will be a wider tappet gap...but it's not unknown for the alloy to crack around the rocker shaft support.

Pleased you caught the cambelt in time,you would be looking at a minimum £1500 for an engine re-build!

Unfortunately the bodykit is known to hide horrors with ease....good luck there.

Post Sat Dec 01, 2012 8:19 pm

Okay took rocker cover off to have a look and found that one of the rockers was broke, exhaust side. which is my problem.
Can this be fixed with out having to take the head off???

Post Sat Dec 01, 2012 8:24 pm

Yes

http://www.e30zone.net/e30zonewiki/inde ... ocker_Arms

Post Sat Dec 01, 2012 9:54 pm

Why would a broken rocker cause a loss of compression?

(or am I being a bit thick?)

Post Sat Dec 01, 2012 9:58 pm

He said that one pot was down on compression, he didn't specifically state that it was the one with the broken rocker.

Post Sun Dec 02, 2012 12:11 pm

Valve could be stuck,causing the rocker to break....

Whilst a broken rocker can be swapped with the head on,it is not the easiest of jobs.The rocker shafts need to be removed,and the easy way to do this is to drift them out from one end.I use a half inch drive socket extention for this,impossible with the head on the engine and the engine in the car! The alternate is to use a lever of some sort to bring the shaft forward,then grip it without marking it,from the front and yank it out...

Given that this engine has stood for a number of years,if it were I playing with it,I would pull the head off and inspect all valves for 'stickyness',cleaning and replacing as needed.

Post Sun Dec 02, 2012 1:20 pm

daimlerman wrote:Valve could be stuck,causing the rocker to break....

Whilst a broken rocker can be swapped with the head on,it is not the easiest of jobs.The rocker shafts need to be removed,and the easy way to do this is to drift them out from one end.I use a half inch drive socket extention for this,impossible with the head on the engine and the engine in the car! The alternate is to use a lever of some sort to bring the shaft forward,then grip it without marking it,from the front and yank it out...

Given that this engine has stood for a number of years,if it were I playing with it,I would pull the head off and inspect all valves for 'stickyness',cleaning and replacing as needed.

+1 remove & strip/rebuild the cylinder head to make sure everythins is at it should be to start with

http://www.e30zone.net/e30zonewiki/inde ... inder_Head

then move a bit further down.

Post Sun Dec 30, 2012 1:58 pm

Ok folks new rocker on, set valves all seemed good. fired her up and all good. put the rocker cover back on started the car giv a few HEAVY revs and she broke a different rocker.any obvious reasons for this??

Post Sun Dec 30, 2012 2:03 pm

jasper25 wrote:Ok folks new rocker on, set valves all seemed good. fired her up and all good. put the rocker cover back on started the car giv a few HEAVY revs and she broke a different rocker.any obvious reasons for this??

daimlerman wrote: Given that this engine has stood for a number of years,if it were I playing with it,I would pull the head off and inspect all valves for 'stickyness',cleaning and replacing as needed.