Off With Her Head 2 | cont...Head Off 3 |
Well - I have my parts from French Marine - minimum bits, ie valve stem seals - Rocker gasket ( it was a bit shot ) and the precombustion chamber lower copper washers.
Its real good to have this pre com chamber out so easily - something I have learned about - once seen, 'understoood' !
My problem now - with all this time on my hands waiting for parts people to open up again after the New Year - I keep measuring specs and thinking - hmmm - how much are new springs etc
The top caps are slightly low to spec - they should be level when the collets are in the retainer. Checking them out, I see its actually one set of collets that are worn. They seem to have worn on the thin inner ring that goes in the valve stem groove. So, actually I only need one pair of collets to get that in spec.
The springs are close to out of spec on the 'leaning over' check - they are 1.3mm out of square which is about the wear limit.
They measure ok for length if that means much ? They work hard all the time and are only £10 each - so its a fair shout to renew them.
So I'm thinking of going half way somewhere. The exhaust vlave is a bit pitted and eroded, but just off the lap ring. Clean on the combustion face though - and good on the seats.
Well - Mon 30th Dec 13. Took another look at the guides.
I checked the valve fit today with some 'oil on the stem' - and then they are much better. Ok to wash everything down etc - but actually these things are running oiled up ! Also - I lapped the exhaust valve when washed off - and it would not lap too well.
Its ok to get a grey layer that looks great all round - but I put the valves in dry and washed off and run them round a bit. The inlet showed little difference, but the exhaust showed a band in the middle, indicating the seat was very slightly domed - ie valve moving a bit while lapping. Surprised me - but then I thought - hey, - well lap it with some oil on the stem. 10 times better - no sign of any middle highspot.
Also - oiling the guides gives you an instant feel that there is any abrasive in there - just a spec and you know it there. Its the way to go if you are lapping valves that are not perfect to spec.
Also - upside down, clean and oiled, the valves are sliding down under their own weight 'slowly' ie they are not dropping thud ! - so am happy now to leave the guides as they are.
More or less decided now on new springs ( they are doing a lot of work ) new cotters and new retainer caps( maybe )
I think the exhaust valve has been blowing by - part of the lack of compression - and there were signs the inner edge of the inlet was leaking slightly
Interestingly - I spent quite a while searching for 120 mm M8 bolts for the alternator. Yes - Amazon and ebay had them - then I noticed they were actually listed as a part on the EPC catalogue( Ribparts site ) and at a very fair price of like £1.50. I am amazed at this site - as to just how many parts are still available as spares for twenty year old engines ( Dyson take note - after-service for older models matters ! )
I cleaned the waterways out with hot kettle descaler - and checked it out for continuity across the flow. Water enters from the block upwards through two inlet holes in the gasket. The small hole by the temp sender - and the larger oval casting hole same side but exhaust side. This then flows across the head to the thermostat housing and on out to the wet exhaust. ( this descaler is basically Formic acid - about 10%. Used cold it is completely useless - so ignore the instructions on the bottle ! )
I then flushed it all out with a hose - dried it in a warm place and liberally dosed it with wd40 to keep the surace rust at bay.
My gasket was completely blocked at the small hole - which must have been affecting the temp sender in my recent overheating episode. The other waterway was open, or I would not have had any flow - but it would restrict the flow around temp sender location. ( It obviously is restricted anyway - hence the small hole one side. Makes sure the temp sender is reading the hottest water, maybe ?
Its good that the head and block have 6 open water ports showing - you can get look in and check whats what. Look good - better than I expected.
Actually - everything is better than I expected on the head. Quite a pleasant surprise really.
I now have to get back down and finish spraying up the engine block etc - I left it treated with Kurust. I'm then spraying it with zinc primer grey - and have used a Ford metallic aerosol for the finish for the closest match to the Yanmar grey. Makes it all a bit tidier looking - but my main concern is to address the weak compression.
My conclusions, at the moment.
When I first got lena she had been laid up badly, in Trowbridge in a car park for many years. Maybe four or five I think. Nothing had been done to this boat in that time - she was just left as she was !
The engine was not protected - or winterised. It was still connected to the wet exhaust. The prefilter was solid with wet rust - etc. However - it had gone in New in 1993 - and was well fitted, ie Vetus waterlock, Vetus hose, Vetus tank - Yanmar loom and mounts etc. It loked all shiney and new !
This was approx 2003 I think. I know the boat was in a yard in Portsmouth somewhere for several years - so actually I doubt whether she had run on the new engine for more than a few seasons - very little !
So - I was always concerned over this engine. When I got to the stage of actually starting it - maybe 2005 - I was well surprised she fired up first time and smoke free, with no actual work done on the injector or injector pump. I merely renewed and cleaned all fuel related things.
For the whole of my first two sailing seasons on the water it ran fautlessly - always started first time, didn't smoke at all - gave me nearly 6 kts flat out - yet, when I was checking it over there was poor compression. I could turn it through the tdc stroke on the crank by hand ? Yet it ran so well - its very odd.
The two years or so I didn't use the boat seemed to do it in some - or maybe something that was always an issue just got worse. Last year was fraught with power issues - but to to fair, it always started. In fact, this engine has only stopped on me once, and has never refused to start at all. That was on the mooring and it had an air leak on a loose fuel connection.
I have done 1200 miles in Lena - so that's not bad going.
Last year - I have had the injector tested and fund to be faulty - replaced with my spare new one. Had the injector pump tested - and rebuilt with a new piston assembly and new delivery valve. New lift pump - all new filters etc and - as a consequence of the overheating, the entire water cooling system checked over, hose by hose, water pump, thermostat, top hoses water lock etc etc.( it turned out to be partially a blocked inlet grating + maybe this blocked head gasket waterway )
It was overheating - as in - just too much for the temp sender ( 62 deg C ) it was not really getting very hot to the touch. I did run it for half a day or so without the sender attached - but kept a very careful watch on the wet exhaust and a direct 'feel' of the engine top !
So with the recent 'slow starting' when its a bit on the nippy side - and still poor compression I decided to take the head off.
The results of that so far is looking good. There are signs the exhaust valve was leaking - signs the gasket was leaking into the tappet chambers ( when I put some oil in the bore I could hear it 'squidging through' somewhere at tdc - and the gasket was covered in oil when I split the head all around the tappet holes. The oil I poured into the bore was still in there the next day, 5mm deep, so I guess the rings are 'intact' at least.
The bore is good looking - no obiously marks. I have yet to really get close with the reading glasses and a torch though !
Once its back on - and I can vouch for the inlet and exhaust valve, precombustion chamber and injector seating - head gasket etc - then if we still have an issue of noticably low comp - it has to be the bore.
From the condition of this head - I have no doubt the bottom end is very sound on this engine. But we could have a ring issue.
As I said, there are oversized piston and rings available | see bottom of this page |
It will be fine for this season I'm sure of that. I'm looking into removing the engine next season. ( see Lena engine page )
The main challenge is removing it - so I will take a look as the year goes on at the mounts. The 'possible' I will nitromors and wire brush back to bare metal and grease - then give them a tweak. The 'unlikely' - I can access for bracket removal - ie split engine from its bracket, rather than bracket from mount. Access for a nut splitter or cordless dremel with a cutting wheel works well.
I don't want to wreck the mounts as they may be ok and salvagable. The engine beds are awful and need renewing. They are like - 3x3 metal angle bolted to the original hardwood glassed in beds. They are rusting away in liberal 'layers' which keep falling off. I'm surprised there is any metal left there. I have tried to treat it, Krust, Hammerite all sorts.
Rather than upset all the angles etc - I should be able to order in some 3x3 heavy gauge Alum and straight swap them. Probably gain a few mm in height ( thicker gauge needed ) so will check the mount height specs. Yanmar only cite 10mm up and down for their mounts. I have the max and min heights.
If I do it on the hard - most likely - I can re set the sterntube if need be. 10mm at the engine - on a maybe, 1200mm prop and tube set up - is very slight rebedding of the cutlass outer bearing. Best though to try to match what is there - these things can be difficult.
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