[All] [Generic] What does 'a valve has gone' mean?

[brgbrm]

In order to get to know something about mechanics I'm looking to buy some cars (non-mr2) that need work doing. I've 2 in mind, one needing a new head gasket, and one where they're not sure what's wrong but have been told a valve might have gone. What does it mean, and what does it mean in terms of work required, when a valve's gone? That's my main Q, the next Q is, whay should head gaskets go on cars with < 70k miles? Does it imply the engines have been mistreated?

Marc

[jon0406]

Not sure about what work would be involved in a valve having gone but in my experience head gasket failure was due to an overheating engine which can be caused by many factors.

On the MK2 golf I have experience of, it was simply a wire to the engine fan which had disconnected itself and caused the engine to overheat, which in turn caused the head gasket to go, it isn't automatically the sign of an engine on its way out.

[simmo490]

both require the head off

a valve gone usually mean either lost its collets (retainers) and dropped in o the bore OR that it has burned out and its not holding compression.

what car is it mate.

depending on the car i would say its a PITA if its only a few hundred profit were talking

simmo

[brgbrm]

Thanks for that. I have to bid on these by tomorrow so that's useful to know.

turn caused the head gasket to go, it isn't automatically the sign of an engine on its way out.

[brgbrm]

Hi David

There's no profit for me here, it's just a learning exercise. Err, I kind of hesitate to admit it here, but the 'valve gone' is on a cinquecento.

Am I right in thinking that bloks don't necessarily have to be skimmed when a head gasket goes? What I'm happy to do is spend many hours getting used to dismantaling things and using tools, but any additional cost opther than buying the car is something I'd prefer to avoid.

Marc

both require the head off

a valve gone usually mean either lost its collets (retainers) and dropped in o the bore OR that it has burned out and its not holding compression.

what car is it mate.

depending on the car i would say its a PITA if its only a few hundred profit were talking

simmo

[RyanRs]

Weather the head / block needs skimming or not isnt something you can tell until the head is off and has been checked with the correct tools..As you may know, metal deforms as it heats up, expecially when under pressure, and depending on how hot it got and how fast it cooled back down, it may not return perfectly to its origional state.

the HG thats currently fitted will follow shape of the deformation but become weaker, until it blows. Fitting a fresh HG on a deformed surface wil cause sealing problems and the HG will fail , how soon,depends on how bad the deformation is...

As for valves... If the valve is losing compression, it could be due to a carbon buildup, which is a simple fix.. it could be in effective valve spring -simple fix, but it could also be cracked seat -expensive!

if a valve has lost its collets and fallen, its very likely it could damage the piston top, Combustion chamber and valve stem.. this means full rebuild and money spent on repairing the head!

[brgbrm]

I once left a saucepan on the hob overnight with the burner still on, so I see what you mean. Presumably I'd need to go to a specialist to get the head checked?

The car with the possible 'valve gone' is desribed as having no power at any time, but making a thumping noise only while going uphill, so that perhaps doesn't sound like there's something in the piston chamber? Although could it fall in, damage it, and then be forced out again?

Weather the head / block needs skimming or not isnt something you can tell until the head is off and has been checked with the correct tools..As you may know, metal deforms as it heats up, expecially when under pressure, and depending on how hot it got and how fast it cooled back down, it may not return perfectly to its origional state.

the HG thats currently fitted will follow shape of the deformation but become weaker, until it blows. Fitting a fresh HG on a deformed surface wil cause sealing problems and the HG will fail , how soon,depends on how bad the deformation is...

As for valves... If the valve is losing compression, it could be due to a carbon buildup, which is a simple fix.. it could be in effective valve spring -simple fix, but it could also be cracked seat -expensive!

if a valve has lost its collets and fallen, its very likely it could damage the piston top, Combustion chamber and valve stem.. this means full rebuild and money spent on repairing the head!

[simmo490]

if it has no power any of the time i would say it aint the valve, but you never know.

taking a cinciento head off is a piece of p1$$ mate and it will be a good start for you, i would say this is one of the best cars to start fault finding etc on.

good choice

[steve b]

Hi David

There's no profit for me here, it's just a learning exercise. Err, I kind of hesitate to admit it here, but the 'valve gone' is on a cinquecento.

Am I right in thinking that bloks don't necessarily have to be skimmed when a head gasket goes? What I'm happy to do is spend many hours getting used to dismantaling things and using tools, but any additional cost opther than buying the car is something I'd prefer to avoid.

Marc

both require the head off

a valve gone usually mean either lost its collets (retainers) and dropped in o the bore OR that it has burned out and its not holding compression.

what car is it mate.

depending on the car i would say its a PITA if its only a few hundred profit were talking

simmo

No don't need to skim it on a fiat, it probably wasn't straight leaving the factory, they just used a nice fat paper gasket to take up the deformation. Its not like multi layer steel gaskets. I got given a uno with a gone headgasket a few years ago, changed it in a morning, didn't bother cleaning up the block more than giving it a rub with a paint scraper, same to the head, sold it to a mate for £50 he ran it all fine for 18months until he crashed it.

[mikey2]

I dont mean to p1$$ on your fire, cos i admire you getting in there and getting the experience through well, experience, but, would you not be better off waiting and spending the money on a mechanical course, that way you will learn the best way ( usually) and have the knowledge to back up what you are doing. I spent 18 months training for my engineering job, and i dont use a lot of the specific stuff i learnt, but, the general engineering and how things should be done and the general knowledge have left me with a great deal of knowledge ( mostly untapped!!).

Getting your hands dirty is a great way to learn, but you would be better off learning from someone who has the skills and knowledge to give you. An engineering course at the right place is worth having if you want to persue it more in depth.

[simmo490]

totally disagree with the above

no replacement with experience and getting it wrong. then looking on the net and books etc for help.

i too am highly quald up and my courses were utter crap and tought hardly anything

simmo

[brgbrm]

Well, I take point your points. As I was looking at ebay re the 2 cars at the weekend, I thought, so how am I going to work on these cars, on my sloping drive and block my proper car in, or move my nice mr2 out of the garage and let an £80 cinquecento nestle out of the cold and rain, whilst my mr2 gets drenched.

I still think the idea of getting something 'disposable' to tinker on is a useful idea, and so is doing a course. I also think it would help me if I assisted someone more (much more! ) knowlegeable.

Simmo, what kind of courses did you do, and hand on heart they can't have been *entirely* useless surely?

[simmo490]

truth be told they did teach me a little but no where near as much as making mistakes.

i was trained by vosper thornycroft and have received a full modern appentiship, city and guilds, NVQ and HND in engineering, including advance diesel technology, Heavy HGV, advance hydraulics and epicyclic gearing.

where is this cink for £80 ??


simmo

[Ian Geary]

in my experience, car repair is 70% having the right size hammer, 25% having a decent heynes manual and only 5% engineering "skill".

when I say hammer, I really mean having the right tool for the right job - reasons why garages can do work a lot faster. also a decent ramp or jack helps.

when I say repair, I mean replacing bits purchased from partco/dealer - not fabricating gears on a lathe, or assembling a block!

And no theoretical course is going to teach you how to line up and bolt on a component whilst leaning upsidedown over an engine with your hand stuck round something rapidly losing circulation.

these knacks take practice.

Or is it just me doing it wrong???

so get in there

Ian

[simmo490]

nail on the head sort of.

however i do believe it requires some skill. some people jsut cannot get the hang of it so it does require some skill.

yes fitting parts from the likes of partco is a start but some people like me like to better them selfs as you say fabricating etc etc.

i get a bit of a kick out of it really. like my quads, i wont buy anything for them i manufacture all my own stuff anything from front A arms to the rear swinger and bearing carrier

simmo

[3sgte]

in my experience, car repair is 70% having the right size hammer, 25% having a decent heynes manual and only 5% engineering "skill".

Ian

Haynes manual ,whats that .
If you cant be bothered to look to see how it comes apart then you shouldn't be putting it back together ROFL

As for torque settings
3 types

1 spanner tight
2 ratchet tight
3 ratchet with 3 foot scaffold pole tight

[simmo490]

haynes book of lies never use them EVER.

[3sgte]

too many people rely on them till the bit where the bolt rounds off .They don't tell you what to do then

[simmo490]

i honestly cannot understand how people can follow a book to fix something. i know some people who take pics but i cannot understand that either

but each to there own, not everyone has out skill level hey 3sgte