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| 16v low/uneven compression; updated with valve gap results... | |
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| Tweet Topic Started: Sat Aug 1, 2009 6:42 pm (1,318 Views) | |
| Uk Merc Man | Sat Aug 1, 2009 6:42 pm Post #1 |
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190e Leg-End
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hi all, 2.5 16v - just about to do a timing chain and tensioner along with valve clearances - they havent been done for ages! thought I would do a compression check to see what the figures were and see if they improve afterwards but, figures are pretty scary..... cylinder 4 is ok with about 140psi but the other 3 are low at 100-110psi..... so, assuming the valve gaps are well out, would adjusting these improve the compression or am i just wishing and its more terminal.... explains the lumpy idle if nothing else - as you'll see from my earlier post, am also doing engine mounts as these are also shot which isn't helping with the engine wobbling round all over the place! thanks. Edited by Uk Merc Man, Wed Aug 5, 2009 9:16 am.
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| big al merc | Sat Aug 1, 2009 6:43 pm Post #2 |
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Highly Addicted
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if they are far out then yes it will affect compression |
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| RobertE | Sat Aug 1, 2009 6:51 pm Post #3 |
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Serial victim...
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Those are low, I must say; I'd have thought that re-shimming would bring them up and into line. But how noisy are they? |
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| viffer | Sat Aug 1, 2009 6:59 pm Post #4 |
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V4 Power
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You need to do a wet test, put a few drops of oil into the bores and then see if the results change upwards. If they do the rings are worn and leaking but you'd also be burning oil? Rule of thumb says the readings should be within 10% of each other and unless you've got the headgasket leaking and overheating, I'd say it's valves causing the problem. Bit the bullet and go for a decoke and valve grind ie topend overhaul but do somemore tests first, the last thing you want to do is jump to conclusions and get it wrong. The down side to owning a 2.3 is there's sixteen valves to grind!! HTH |
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| jeremy | Sat Aug 1, 2009 7:04 pm Post #5 |
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Too Far Gone To Help
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Aren't they supposed to be around the 170 mark ? Jeremy |
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| merc190uk | Sat Aug 1, 2009 7:46 pm Post #6 |
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The Godfather
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that was my first thought
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| cossie connoisseur | Sat Aug 1, 2009 8:13 pm Post #7 |
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there can be only one ;-)
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all well low, also as they vary it means your engine will be lumpy and vibrate a lot (same as if the engine suspension was dud) do the leak test to eliminate rings then most likely it would be a head off job....worse case anyway pretty common thing on a 16v even a well looked after one has it happen |
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| Will | Sat Aug 1, 2009 9:41 pm Post #8 |
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Highly Addicted
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Almost certainly a top end issue. What's the mileage, has it ever been apart before? I'd bite the bullet and whip the head off. If it needs a chain replacement and re-shimming it's already half way there. Only additional costs would be a set of gaskets/seals and the head bolts (unless there's something amiss, which you might as well find out sooner rather than later). Re-shimming it would probably help a lot, but a de-coke and freshly lapped valves is what you really want IMHO. Will Edited by Will, Sat Aug 1, 2009 9:41 pm.
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| Johnboy Mac | Sat Aug 1, 2009 11:11 pm Post #9 |
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More than part of things
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+1 |
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| Uk Merc Man | Sat Aug 1, 2009 11:54 pm Post #10 |
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190e Leg-End
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its got 154k on it with full history. doesnt burn oil and no smoke to from exhaust to indicate it. plugs are also dry and well coloured..... previous 16v's i've tested have show bewteen 140-150psi albeit with a fair bit lower mileage........for now I'll do the chain and tensioner and valve gaps and see where it takes me - its my only car so dont really want to have to pull it all apart...... at least I know the valve clearance should at least help a bit....its not really that noisy but then I guess if they were tight it wouldnt be? still, parts are on order and the cars in pieces......the joys of 16v ownership! |
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| merc190uk | Sun Aug 2, 2009 12:18 am Post #11 |
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The Godfather
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welcome back to the world of 16v bud i remember how silent that engine was and very suprised by it so maybe it needs the shims a bit more open have you taken a valve gap reading yet ? if so what did you get |
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| cossie connoisseur | Sun Aug 2, 2009 2:20 am Post #12 |
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there can be only one ;-)
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flaming hell steve what did you do take it on a track day and do a clarkson and race a scoobie or something? anyway do what you said and that will improve things however even if the mix is out a bit a coke build up is inevitable which will lead to excess valvewear head off on a 16v generally leads to other 'expenses' at th end of the day its drivable, just a bit lumpy and slower than a sorted one. |
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| Will | Sun Aug 2, 2009 8:06 am Post #13 |
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Highly Addicted
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Be interesting to see what the valve clearances are. Could you post them up when you've measured them Steve? My guessing is that the exhaust side will be on the tight side, perhaps some with even zero clearance, causing the valve to stay partially open even on the compression stroke. That will explain the low compression figure. The inlet side may have worked loose, but if it's as quiet as you say, perhaps it won't be far out. There really should a mercedes190.co.uk 'shim swap kit' for people doing the shims, a few dozen shims of differing thickness - borrow the kit, swap the shims around to what you need, and donate £20 or so to buy a few more! Will |
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| RobertE | Sun Aug 2, 2009 8:17 am Post #14 |
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Serial victim...
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That's a good idea, Will. I've been collecting them against the inevitable day when I'll have three engines to do. A 'shim library' sounds just the job. |
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| jeremy | Sun Aug 2, 2009 8:47 am Post #15 |
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Too Far Gone To Help
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I am going to be doing my shims this month . So hopefully I can get the ball rolling on this . Jeremy |
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| Uk Merc Man | Sun Aug 2, 2009 10:12 am Post #16 |
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190e Leg-End
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i'm still playing silly beggars with the exhaust side engine mount, once thats done i'll whip the cover off and measure up.......fingers crossed thats all it is....i'll post up my measurements when I do it.... thanks for the help so far cossie - what are you talking about??? Edited by Uk Merc Man, Sun Aug 2, 2009 10:13 am.
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| Desmoboy | Sun Aug 2, 2009 10:29 am Post #17 |
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Part of things
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If it wasn't for the fact that that they are uneven rather than just being low it could have been a timing chain jumped issue. Still possible i suppose. Has it been getting gradually slower or was there a step jump all of a sudden? When i had mine apart last year to do the shims i discovered that the inlet cam was 2 teeth late in opening and the top chain support was broken. Either it had jumped or been put back together wrong by the "expert" employed by the previous owner. Might have explained why he sold it as well. Anyway, the compression was 8 bar before and in excess of 12 after. Goes good now ! |
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| marcus.hopkins | Sun Aug 2, 2009 11:13 am Post #18 |
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Administrator
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Bloody hell steve ![]() Apart from the lumpy idle the car doesnt feel under powered, does it? I have never noticed a lack of power and pickup is good. I was told that the idle issue was due to the need of a re shim so i am preying that is correct. And no desmoboy that isnt why i sold the car as i actually had no intention of parting with the 2.5-16 until steve offered me a deal. On the face of things i have always though of her as a damn good car and am actually quite disappointed at steves findings which are very unexpected. Speak soon steve. Marcus Edited by marcus.hopkins, Sun Aug 2, 2009 11:45 am.
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| RobertE | Sun Aug 2, 2009 12:18 pm Post #19 |
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Serial victim...
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I'd suggest a good drenching with upper cylinder lubricant and see what the effect is (usually something in my experience). It was a critical issue with Astons (no shims there, you have to grind the effing valve stems) and Jaguar XKs (shimmed). Both types of engine tend to overfuel, (SU carbs) rather like 190 valvers. This produces varnished gunk deposits on the piston rings, making them stick and cruddy build-up on the closing faces of the valves and seats. Plugs won't show this. You might be surprised! So, give it a gargle with RedEx, Wynn's, STP, whatever before investigating clearances and putting the old girl off the road while you wait for the shims to arrive. Fingers crossed! Edited by RobertE, Sun Aug 2, 2009 12:19 pm.
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| viffer | Sun Aug 2, 2009 1:46 pm Post #20 |
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V4 Power
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Another option is to get a second hand head, clean it, new oil seals, grind the valves so it's ready to fit, you then have a bit more control over the whole procedure. If the valves are leaking where they sit, it's a head off job. If your readings were the other way round ie one down you'd still need to get the head off because there's a problem and it's not going to go away. You've a tired head, a good decoke will transform it. There was a time when decokes were part of a routine service schedule, a lot of stuff to take off these days before you can get at the head but it's quite satisfying once you've done it. |
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| Big Ben | Sun Aug 2, 2009 1:56 pm Post #21 |
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Sneaky 2.5-16 Driver!
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Fingers crossed the valve guides are ok! I have a problem deciphering what Nick means occasionally too mate, and I'm his Dad!
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| Uk Merc Man | Sun Aug 2, 2009 4:04 pm Post #22 |
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190e Leg-End
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the car actually drives ok, i certainly wouldnt have guessed by driving it that the compressions were so low/uneven. the car picks up ok and power seems fine albeit a little lacking at the very top end of the revs......the idle is poor as well, evenso.........will start pulling it apart over the next few days - chain and tensioner are already ordered, I've measure the gaps and get the shims ordered this week - we'll see what happens. at the moment i'm rolling in the other halfs seat arosa - quite a come down from an AMG!! lol! |
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| cossie connoisseur | Sun Aug 2, 2009 5:08 pm Post #23 |
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there can be only one ;-)
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what i was saying was that if the fuel mixture is out even by a tiny bit then the head really hates it and normally when you take the head off all you get is black muk which has worn the valves early. i doubt your rings are and issue and mabie reshimming will solve it....however what you describe is classic valvewear tbh when you apply power when stationary to move off does the car strugle a tiny bit and want to stall?do you have to compensate for more throtle and less clutch? |
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| Desmoboy | Mon Aug 3, 2009 5:41 pm Post #24 |
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Part of things
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Hi Marcus Misunderstanding, i was talking about the car i bought and the possible reason the previous owner sold it to me because he could not understand why it wasn't running well. Didn't mean you at all. As to the car in question here, if it appears to run perfectly well in all other respects but it just has a low compression reading , perhaps a different compression tester might be an idea. keith |
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| Uk Merc Man | Mon Aug 3, 2009 8:46 pm Post #25 |
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190e Leg-End
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already tried 2 testers......anyway, havent got any definitive results as yet (dinner was ready early!) but all the gaps are very tight, couldnt even get a feeler gauge into some of them, inlet and exhaust - smallest gauge I have is 0.15mm - do you think this points to the valve gaps causing a problem, they're obviously wrong!! |
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| Johnboy Mac | Mon Aug 3, 2009 9:47 pm Post #26 |
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More than part of things
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Good news. |
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| Uk Merc Man | Wed Aug 5, 2009 8:05 am Post #27 |
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190e Leg-End
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right - current valve gaps...talk about tight!!!!! out of the 16 valves, 10 of them are so tight I cant get my smallest feeler gauge (0.15mm) in there, the other 6 are all 0.15mm - the next gauge up (0.20mm) wouldnt fit. can someone confirm the 2.5 16v valve gaps in MM - I dont have the sticker on the slam panel..... i guess these valve gaps aren't helping? thanks |
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| Big Ben | Wed Aug 5, 2009 3:11 pm Post #28 |
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Sneaky 2.5-16 Driver!
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Inlet = 0.10 to 0.20 Exhaust = 0.25 to 0.35 Thats mm of course! |
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