how do you know cam is gone
Discussion
Hiya,
This topic has been discussed in some detail that you may find useful here:
www.pistonheads.com/gassing/topic.asp?t=239675&f=8&h=0
I found out that the cam was knackered when it went in for the 'Mark Adams Chip' and they did a diagnostic run on the rolling road and then spent nearly a whole day figuring out what was wrong! The most noticeable thing was a severe loss of power.
Cerby4.5
This topic has been discussed in some detail that you may find useful here:
www.pistonheads.com/gassing/topic.asp?t=239675&f=8&h=0
I found out that the cam was knackered when it went in for the 'Mark Adams Chip' and they did a diagnostic run on the rolling road and then spent nearly a whole day figuring out what was wrong! The most noticeable thing was a severe loss of power.
Cerby4.5
I'm beginning to think mine may be on its way out - tapping sound evident from rockers at idle and gets worse at around 2000rpm. Its a 400 Chim, 1995 done about 70k miles. Engine power doesn't seem too bad - seem quick to me although I’ve only had the car a few months so wouldn't know if it was down on power or not! Strange thing is that the power seems to kick in about 3000rpm - wouldn't a worn cam be worse at higher rpm or doesn't it work like that? Also the exhaust note seems to have a strange resonance - doesn't seem to sound right - sounds as if the engine is missing when it isn't (same sound occurred but a lot worse when one of my ignition leads was shorting to the exhaust i.e. missing on one cylinder) All the plugs look OK - no differences between them.
I'm going to remove the rocker covers this weekend and examine the rockers/shaft for wear (this could explain the tapping) and also measure the lift with a DTI - if there are any differences between the cylinders this should tell me if I have a worn lobe(s) on the cam.
Toby.
I'm going to remove the rocker covers this weekend and examine the rockers/shaft for wear (this could explain the tapping) and also measure the lift with a DTI - if there are any differences between the cylinders this should tell me if I have a worn lobe(s) on the cam.
Toby.
rnd said:
I am always hering people saying that their car needs a new cam but what are the symptoms. Mine is not knackered but am intrested in how people know. (hope i never have to worry about it).
Ray is this an excuse for a new cam? or maybe that Chimaera 500 on ebay, would my the S fly!
When you say 'chuffing' sound what do you mean? - Probably hard to describe?
My car is making a sound that seems strange to me (although maybe normal as this is the first chim I’ve had!) - its a bit like a resonance in the exhaust - only occurs under light throttle loads though. It sounds a little like when its not firing on all cylinders, but no where near as bad as that.
I assume the compression test would show up cam problems because the values won't be opening at the same time on all cylinders so the volume of air going into the cylinder before the compression stroke will be different??
My car is making a sound that seems strange to me (although maybe normal as this is the first chim I’ve had!) - its a bit like a resonance in the exhaust - only occurs under light throttle loads though. It sounds a little like when its not firing on all cylinders, but no where near as bad as that.
I assume the compression test would show up cam problems because the values won't be opening at the same time on all cylinders so the volume of air going into the cylinder before the compression stroke will be different??
jonathant said:
my chim 450 started making a "chuffing" sound which turned out to be a worn cam (and chipped valve). I wouldn't have thought a compression test would show up a worn cam? Surely the valves just don't open as far as they should....
Tobs said:
I assume the compression test would show up cam problems because the values won't be opening at the same time on all cylinders so the volume of air going into the cylinder before the compression stroke will be different??
Yes, I think that's the theory. It's not that the actual compression is low, it's that on the induction stroke the inlet valve hardly opens and is open for a shorter than normal time. So a partial vacuum is created, not as much air is drawn in, so there's not as much to compress and compression appears low.
Tobs said:
When you say 'chuffing' sound what do you mean? - Probably hard to describe?
indeed. <grimace> kinda sounded like a faint steam train on top of the usual racket that goes on up front. Oh, also, it felt like there was no power until about 3000rpm when the engine took off as "normal".
Hmmmm.... from what you describe, maybe my cam is on its way out then. I do have a lack of power below about 3000rpm - then it takes off. I would have thought though that it would be a lack of power at high revs with a worn cam? Have to say though, my fuel economy is not too bad a the moment though – drove 350 miles yesterday and got just over 30mpg !! (all motorways and A roads). On my normal daily commute I average about 16-17mpg…. Worst being 13mpg…
My engine also seems very tappety - and the rockers don't look too worn themselves (i took the cover and rocker assembly off the passenger side to have a look). I also know my exhaust gaskets could do with changing - I can hear them leaking when I put my foot down - but that is a different kind of noise - less metallic. I also get lots of popping and banging on overrun (along with the noise from the tappets) - maybe more than you are supposed to get?
As for the 'chuffing' sound you are talking about - seems more like a resonance in the exhaust in my case – definitely a reverberation of some kind though - just doesn't sound right. I may try to get a recording of the sound tomorrow so people can listen and say what they think!
Think I’ll have to lift of the inlet manifold this weekend and take a look at the cam! I was planning to replace the exhaust manifold gaskets, but I'll check the cam first to see if this needs changing and if so i'll do the lot at once! I assume i'll just need a new valley gasket to put it back together after checking the cam?
Toby.
My engine also seems very tappety - and the rockers don't look too worn themselves (i took the cover and rocker assembly off the passenger side to have a look). I also know my exhaust gaskets could do with changing - I can hear them leaking when I put my foot down - but that is a different kind of noise - less metallic. I also get lots of popping and banging on overrun (along with the noise from the tappets) - maybe more than you are supposed to get?
As for the 'chuffing' sound you are talking about - seems more like a resonance in the exhaust in my case – definitely a reverberation of some kind though - just doesn't sound right. I may try to get a recording of the sound tomorrow so people can listen and say what they think!
Think I’ll have to lift of the inlet manifold this weekend and take a look at the cam! I was planning to replace the exhaust manifold gaskets, but I'll check the cam first to see if this needs changing and if so i'll do the lot at once! I assume i'll just need a new valley gasket to put it back together after checking the cam?
Toby.
I saw my cam this afternoon and it has worn and needs replacing. I was blissfully unaware although it was at a fairly early stage - given another 1000 miles and it would have been (more) obviously down on power. The trouble is it is such a gradual thing it's very easy to just think you're getting used to the power. I have had moments when I've wondered but then I take someone out who doesn't know the car and they are always blown away at how quick it is - it just reassures you there is nothing wrong.
One short drive by the chap who looks after my car and he knew straight away all was not well. How annoying is that?! I know every little squeek, rattle and foible of my car and I didn't spot it!
One short drive by the chap who looks after my car and he knew straight away all was not well. How annoying is that?! I know every little squeek, rattle and foible of my car and I didn't spot it!
I've just bought a compression tester - will give this a try before I lift off the inlet manifold to see what's going on.
By the way is it possible to temporarily re-use the valley gasket (with say some gasket sealant) as long as it is not damaged when removing the inlet manifold? I'm asking because I don't think I’ll be able to get a replacement by the weekend (tomorrow!), otherwise I will have to wait until next weekend. Also if the cam does need replacing I would have to renew the gasket again!
Toby.
By the way is it possible to temporarily re-use the valley gasket (with say some gasket sealant) as long as it is not damaged when removing the inlet manifold? I'm asking because I don't think I’ll be able to get a replacement by the weekend (tomorrow!), otherwise I will have to wait until next weekend. Also if the cam does need replacing I would have to renew the gasket again!
Toby.
Tobs said:
Hmmmm.... from what you describe, maybe my cam is on its way out then. I do have a lack of power below about 3000rpm - then it takes off.
Doesn't that sounds more like a lambda feeback issue than a cam issue. The ECU switches to open loop at around 3000rpm (ignores lambda sensors) and hence any fuelling issues can be masked.
I would get your lambda sensors and fuelling checked.
Ian A.
IPAddis said:
Doesn't that sounds more like a lambda feeback issue than a cam issue. The ECU switches to open loop at around 3000rpm (ignores lambda sensors) and hence any fuelling issues can be masked.
I would get your lambda sensors and fuelling checked.
Ian A.
Yes I did think it could also be that - but the poster above said that had had this when his cam was on his way out. I've checked the ECU recently when I had an issue with the Air flow meter. (Turned out to be the flow meter full of water!). The Lambda's seemed to be doing their job, fluctuating between 0 and 1 volts. However, as I said above though, I agree in that I'd have thought cam problems would show up at higher revs rather than lower ones?
Anyway I'm going to do a compression test and lift off the intake manifold so I can have a look at the cam - I think this is really the only way to find out conclusively if it is worn or not.
Well, I did the compression test, and all cylinders were between 161-170psi - all within about 5% seems good to me 
. Because of this I didn't bother lifting the inlet manifold to take a look at the cam, but checked the drivers side rockers and shaft. There is a little wear present, as would be expected after 70k miles, but all looked OK. All the lift on the rockers seems to be the same too. So I think my cam is OK...
I also replaced the drivers side exhaust gasket, (B
RD of a job that was!) as I knew this was leaking. And while I was at it replaced the drivers side engine mount (It's easier to do without the exhaust in the way!), and painted the top of the chassis rail under the manifold.
Engine now sounds much much better, however there is still a slight ticking sound from the rockers on the drivers side - maybe I’ll still have to take the inlet manifold off to examine the tappets. I think I’ll change the passenger side exhaust gasket first though when I get chance (and my hands have recovered!) as the noise may be coming from there!
If it is a tappet that's causing the problem is there some engine oil additive you can use to clean them out?
Toby.
. Because of this I didn't bother lifting the inlet manifold to take a look at the cam, but checked the drivers side rockers and shaft. There is a little wear present, as would be expected after 70k miles, but all looked OK. All the lift on the rockers seems to be the same too. So I think my cam is OK... I also replaced the drivers side exhaust gasket, (B
RD of a job that was!) as I knew this was leaking. And while I was at it replaced the drivers side engine mount (It's easier to do without the exhaust in the way!), and painted the top of the chassis rail under the manifold. Engine now sounds much much better, however there is still a slight ticking sound from the rockers on the drivers side - maybe I’ll still have to take the inlet manifold off to examine the tappets. I think I’ll change the passenger side exhaust gasket first though when I get chance (and my hands have recovered!) as the noise may be coming from there!
If it is a tappet that's causing the problem is there some engine oil additive you can use to clean them out?
Toby.
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