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r1chm
East Yorkshire,
United Kingdom

Posts: 494
Daytona T595


icon12 May 2018 23:03
Hi All

Thanks for everyone'es suggestions previously with a weird noise on my mates car - turns out it was the rear diff. Its been reconditioned and is now quiet.

I have an issue with my own car now, and I think I have diagnosed it as terminal but I just wanted some more experienced opinions before I scrap it.

Last week I noticed an obvious drop in power from the engine, regardless of RPMs. It felt like the car was in Limp mode but would rev freely out of gear/with clutch pressed. At the same time, when I put my foot down it sounded like my exhaust was blowing so I assumed that was the issue and planned on fixing it this weekend.

I noticed on Friday that with engine running if I pulled dipstick/oil filler cap there was significant suction being drawn into the crank case. A bit of googling suggested this could be worn piston rings or a blocked CVS valve. I was leaning more towards the CVS as there was no noticeable smoke or over the top oil consumption.

The car is an old 2008 Astra 1.6 with 182k miles on it so I don't particularly want to spend alot of money on it, albeit it is in good condition cosmetically and is LPG converted so cheap to run !! :smile:

This morning before throwing money at it for new a new CVS I compression tested the cylinders. Cyls 2,3 and 4 were all OK but Cyl 1 was way down.

This leads me to believe it will be 1) piston ring 2) valves or 3) potential HG failure.

Piston Ring - as said, no obvious smoking/oil consumption so I don't think it is that.

HG failure - maybe, but no mixing of oil/water in the oil or coolant reservoir. It could have failed to the outside of the block but i would expect to hear it/see smoke or oil but I cant find anything.

Valve(s) - likely culprit in my opinion but I've heard that a bad valve would eventually allow the pressure to escape from the cylinder following a compression test, which didnt appear to happen. I tested this by performing the compression test then going for a cup of tea for a half hour or so - when I came back I pressed the button to release the pressure on the gauge and heard the expected 'whoosh' of expelled air so I believe it held pressure.

That said, I still think valve(s) is the likely culprit in which case its not worth fixing.

Any other thoughts/opinions what it might be?

The car starts fine hot or cold. When idling, there is a slight "hunting" of RPM but it has done this for at least 2 years. When driving, until last week when the loss of power happened, the engine pulls smoothly and isn't misfiring.

Sorry for wall of text...
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Rob NMTB
Redditch,
United Kingdom

Premier Member
Posts: 54,464
Speed Triple 1050


icon13 May 2018 07:55
If compression is way down on 1 cylinder, it has to be rings or valves, which is going to cost a few £, either way 01
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McWill
scotland,
United Kingdom

Sprint ST (05->)


icon13 May 2018 08:51
182k Astra hardly worth spending any money on...... unless the cars in really good condition otherwise.
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norbsa2
Kent,
United Kingdom

Premier Member
Posts: 1,395
Daytona 1200


icon13 May 2018 09:02
Try compression test on cylinder 1, then put teaspoon of oil down plughole and retest. if compression is up then problem with rings, if no change then prob valves.
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jaguartvr
Englefield Green,
United Kingdom

Posts: 4,588
Enthusiast


icon13 May 2018 09:51
norbsa2:
Try compression test on cylinder 1, then put teaspoon of oil down plughole and retest. if compression is up then problem with rings, if no change then prob valves.



+1:thumbup:
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Gazmo65
East Midlands,
United Kingdom

Premier Member
Posts: 531
Enthusiast


icon13 May 2018 10:22
Depending on how much work you are able or willing to do , if its rings then you should be able to drop the sump off and remove the offending con rod and piston, replace the set of rings and then replace for the cost of a sump gasket and set of rings and probably exhaust gasket, it can be a bit of a struggle but its mainly a case of taking your time.

If you find its the valves then it's more of a ball ache and minimal costs would be replacement valve or valves head gasket timing belt coolant and oil, the valve seat may be worn but that can be lapped in and you could also need valve stem seals, again its time and effort, modern engines are a total pain when it comes to plastic breather pipes etc as they can become brittle so care is needed as the cost can mount if you break and have to replace them.

What is the cost of a secondhand replacement engine and would you be able to do the replacement yourself, but then you still have a timingbelt and waterpump to replace and might as well do the clutch whilst your at it, it soon mounts up

When your in this situation I agree with the scrappage deals offered by dealers some are offering up to £5000 at the moment but I personally couldn't afford to buy a new car and would try the cheapest option above first or take the hit and get another second-hand car, what mileage do you do and could you not just continue using the car until it eventually decides enough is enough, that's a bit like burying your head in the sand and could be a huge inconvenience.
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Paul Pomodoro
Sth London / Surrey,
United Kingdom

Premier Member
Posts: 876
Bonneville (09->)


icon13 May 2018 15:20
Isn't it worth checking the valve clearances on cyl 1 just in case the lack of compression is due to a clearance being too tight and a valve not being fully closed?
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Nige
Tuesday so must be,
Belgium

Premier Member
Posts: 7,657
Speed Triple 955i (02-04)


icon13 May 2018 16:12
+1. A good point to tick off before moving forward.
Next I would ask if it’s consuming coolant..? I know it’s theoretically possible for it not to happen but generally a blown HG will either pressurize the cooling system or pass coolant in to the oil, or both. Have you removed the rad cap and looked for bubbles in the coolant..?
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lord stuart
derbyshire,
United Kingdom

Premier Member
Posts: 24,219
Daytona 955i (99-01)


icon13 May 2018 17:33
If it's lpg converted, lpg is very acidic, those 4 litre range rovers that are converted used to actually have holes just above piston ring tdc, in the cylinder wall.:lol:
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r1chm
East Yorkshire,
United Kingdom

Posts: 494
Daytona T595


icon13 May 2018 20:01
Hi all, thanks for input.

Its not using excessive oil or losing coolant.

You've pretty much confirmed by suspicions re the valves though. No one has come back and said it may be something which is dead easy to check/change. :lol:

As stated, the engine isn't worth spending the cash on given its mileage. Im currently weighing up buying a 2nd hand motor for 300 and having it fitted, it just depends on fitting cost as whilst i'm reasonably OK with a spanner i don't have an engine hoist or the space to tackle it myself.

Failing that I've seen a half decent Mondeo for sale not too far away with 77k miles and FSH. Seen loads of them on ebay with 200k+ miles so they must be fairly reliable if looked after!

Cheers
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Sir Alan of Ingol
sespit of the north,
United Kingdom

Posts: 13,832
Enthusiast


icon13 May 2018 20:15
from memory are the valves actuation not hydrolic (sp) ,no no setting needed , although they can fail , and PS , you will not be able to change piston rings via removing sump , the head needs to be removed
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Mach 1
Durham,
United Kingdom

Posts: 1,117
Bonneville (01-08)


icon13 May 2018 20:38
Sir Alan of Ingol:
from memory are the valves actuation not hydrolic (sp) ,no no setting needed , although they can fail , and PS , you will not be able to change piston rings via removing sump , the head needs to be removed


Correct on both counts :thumbup:
No matter if the problem is head gasket , valves or piston , the head will have to come off , the piston comes out from the top :thumbup:
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Gazmo65
East Midlands,
United Kingdom

Premier Member
Posts: 531
Enthusiast


icon13 May 2018 20:49
Sir Alan of Ingol:
from memory are the valves actuation not hydrolic (sp) ,no no setting needed , although they can fail , and PS , you will not be able to change piston rings via removing sump , the head needs to be removed
Mach 1:
Sir Alan of Ingol:
from memory are the valves actuation not hydrolic (sp) ,no no setting needed , although they can fail , and PS , you will not be able to change piston rings via removing sump , the head needs to be removed


Correct on both counts :thumbup:
No matter if the problem is head gasket , valves or piston , the head will have to come off , the piston comes out from the top :thumbup:


I have replaced rings and piston on cavalier 1.8 engines in the past from below by removing the sump and read in car mechanics magazine that they have done the same on an insignia
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Sir Alan of Ingol
sespit of the north,
United Kingdom

Posts: 13,832
Enthusiast


icon13 May 2018 20:52
did you remove the crank as well , piston is larger than gap at side of crank

there again , after 40 yrs of working on cars I must know f!$% all
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----KK----
West SX / London,
United Kingdom

Premier Member
Posts: 41,391
Enthusiast


icon13 May 2018 20:55
Did any of them work afterwards?












:tongueout:
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Mach 1
Durham,
United Kingdom

Posts: 1,117
Bonneville (01-08)


icon13 May 2018 22:50
Sir Alan of Ingol:
did you remove the crank as well , piston is larger than gap at side of crank

there again , after 40 yrs of working on cars I must know f!$% all


Every car I've changed a piston on has been from the top but potentially there may some that can be done from the bottom .As Sir Al said , there's normally not the room to get the piston past the crankshaft webbing. I've done a couple of 1.6 VRX Corsa's , prone to cracking piston rings especially when ecu is chipped, and that involved head off .
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Nige
Tuesday so must be,
Belgium

Premier Member
Posts: 7,657
Speed Triple 955i (02-04)


icon14 May 2018 12:54
r1chm:
Hi all, thanks for input.

Its not using excessive oil or losing coolant.

You've pretty much confirmed by suspicions re the valves though. No one has come back and said it may be something which is dead easy to check/change.

So if it's not using oil or coolant that would lead me to believe that most likely the pistons/rings are sound, as is the head gasket. The only option left to consider after that is therefore the valves. It's not a difficult job to whip a head off, let's face it what do you have to lose because if the engine's toast all that removing the head will do is confirm that fact and would leave you with the following options: -

1. Refurb/replace the head depending on how bad the one is that comes off. Not a big job for a half-competent mechanic - a day's work at most IMHO. Where you would find a competent mechanic on TT is open to question though....... :speechless:
2. Replace the complete engine.
3. Replace the vehicle.
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