I have to say I've never heard of the phrase wet and dry compression test. Normal procedure is to run the engine to ensure adequate oil distribution around the piston rings, then allow engine to cool sufficiently to insert the probe (either threaded into the spark plug hole or a rubber cone which is held manually onto the spark plug seat)
I'm inclined to think that the primary cause is not likely to be worn or broken piston rings, if that was the case you'd be having blue smoke all the time rather than just sometimes.
I would suspect that the sudden dropping of revs as you begin to change gear, followed by foot on accelerator as the next gear is taken up, is causing a vacuum which is drawing oil into the cylinders which in turn causes an over-rich mixture (hence revs fall away again) and then blue smoke as the oil is burnt off. That is very very damaging for your catalytic converter!
These engines are very prone to condensation which forms a yellow 'mayonaise' in the rocker cover and in the hoses associated with the emission control system. This prevents them from working properly.
I would start by taking off the oil filler cap. It normally incorporates a flame trap made up of wire gauze and also a PCV valve. The PCV valve (Positive Crankcase Ventilation) valve allows oil vapour from the crankcase to exit (via the rocker cover and the oil filler cap) and then enter the inlet manifold (normally via the air cleaner housing) to be burnt up in the cylinders. Therefore check that the oil filler cap is not sludged up, it can be cleaned with out with parafin and an air line. Also remove the hose that connects it to the air cleaner housing and ensure the hose itself and the fittings at either end are not sludged up. Open up the air cleaner housing and check the inlet hole inside is clear.
Note that some versions of this engine have the PCV valve inside the air cleaner housing instead of in the oil filler cap. It looks like a little flat rubber mushroom about 12-15mm diameter. Its just a push fit so take it off and clean up the hole. If the PCV valve has not been changed for years put in a new one, its a very cheap but vital part of the emission control system. Likewise I would consider changing the air filter, if it has had bursts of oil vapour it may be sufficiently soaked as to restrict the airflow through it.
If the inside neck of the rocker cover is sludged up with mayonaise I would also take the rocker cover off and clean it out, you'll be amazed at how much of that horrible yellow stuff can be inside.
I dont know whether or not the above will cure the problem but, in any event, if you find mayonaise sludge its a job that needs to be done anyway as part of working through a tune-up.
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Just to expand on what JC has written,
First ensure that there is no debris in the area of the spark plugs before you remove them. (See posts on seized spark plugs as well.....)
Disconnect the ignition coil.
Fit the compresssion tester to number one cylinder. (Pulley end)
Floor the accelerator pedal, and crank the engine over for 15 seconds.
Record the reading, and do the same for the other three cylinders.
You now have the results for a "Dry" test.
Remove the compression tester. And give three squirts of an oil can down number one bore.
Fit the tester, and carry on as before, but with the oil addition before each test on a new cylinder.
You now have the results of a "Wet" test.
Post the results of both, and I'll tell you what I think of them. Note that when the car is put back together, she will smoke like a Vatican chimney, so make sure you are not too close to the house.... (Or a main road.) And drive the car untill the smoke clears.
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Tony, thanks for that explanation of the phrase 'dry and wet' in this context, I hadnt it heard expressed that way before.
The only thing I would add is that my instruction sheet states that the engine should be warmed up first and that a cold engine will not give an accurate reading. I've checked online and found similar statements. For example:
www.nicoclub.com/articles.php?id=159838
www.automedia.com/Engine_Compression_Test/ccr20050...2
www.search-autoparts.com/searchautoparts/article/a...0
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Hi all,
Thanks for that - i'll check the breather shortly - and try the compression test at the weekend.
Cheers for the help!
James
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Claude,
Yes, you are quite right, I forgot to mention that the engine should be hot.
James.
Is this fault only there when changing gear? And is the smoke only there after the jerking?
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Hello all,
The fault is apparent about 15secs after changing gear then lasts for about 15-30seconds and clears. It goes away until you have to foot-off again.
So - an Update!
Changed the PCV filter thingy on where the oil goes in. It was full of gunk as Claude said. The head looks to have some in too - but thats another day. Also cleaned out the air filter box as was full of bits of crap.
Took the car for a 20 min test drive and so far so good. The problem has didn't show itself!!!! :-)
I'll keep an eye on it over the next few days - cause initially when I got the car it took a few days to show.
I wonder whether that filter was blocked proper - i.e. it would take time to build pressure before dumping into the cylinder? (if I understand this correctly).
Thanks all - again - for the help!! Amazed if something so "simple" cures it!!!!!!!! (the previous owner spent ££££ trying to get it to work at various garages - long story)
James
PS - i'll probably cut the old filter up and see whats in side out of interest!
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Oh - did some reading on the links provided (and found the bit in Haynes randomly) - interesting some don't say to disconnect the fuel pump fuse - surely a requirement or wouldn't fuel spray everwhere!!!????
James
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yes it will squirt fuel but only into the bores, and as there is no spark it should not ignite, also as the engine is warm it would vaporise, not only that but having foot nailed to the floor plenty of air entering engine and having foot down on pedal usually the fuel won't be injected (different cars behave differently with regards to fuel being injected as most modern cars wont start if the throttle is touched) do you know where the fuse/relay is situated
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Hello,
Yup I know where they are on this car.
Thanks for the clarification - i'll pull the fuse anyway for safety.
That said the car ran perfectly again this AM - so might be put off by the cold weather and leave it till its warmer - assuming it continues to behave...!
cheers all,
James
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Good result, I'm pleased it worked out so well.
When you do your next oil change (sooner rather than later) I'd suggest using a flushing oil which will help clear that gunge out of the oil galleries. Also, when you are draining the oil from the sump, is a good time to take the rocker cover off and clean up. Any paraffin you use to clean the gunge off the rockers themselves can then drain down into the sump and run straight out of the drain plug.
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me too! :-)
Thanks again for your help!
James
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Any paraffin you use to clean the gunge off the rockers themselves can then drain down into the sump
Via the camshaft and tappets!
Personally I'd just clean up the cover if required, flush out the meshed cap in some spirits, and check the breather hoses for blockages.
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No, its not via the camshaft and tappets. At least not in the sense that I think you mean. ie: across those bearing surfaces and hence likely to cause damage.
The engine oil is pressurised from the oil pump upwards via the oil filter and then through all the oil galleries and bearings (including the camshaft and tappets) eventually emerging out of the rocker cover shaft at the top of the engine. Its return path is via gravity down the drain holes into the sump, not back down through all the bearing surfaces. (If it wasnt that way you would never be able to fill up the sump by just pouring oil into the top of the engine!)
I'm not suggesting pressure washing the rockers with paraffin! That might send paraffin who knows where. But its not really possible to clean up the top of the engine with just a dry wipe. A bit of paraffin is helpful around the rockers themselves aided with a small brush where necessary. Even a pipe cleaner down some of the holes. Inevitably a small proportion of paraffin might find its way down the drain holes. The point I was making is that, if this cleaning is done whilst draining the oil from the sump, those paraffin washings will drain out of the sump at the same time. Its certainly worked for me over many years and I've never had any problems with camshaft or tappets, either on the Endura engine or the earlier HCS engine on which its based. I've had seven cars with this engine over the years.
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Have a look what's down those "drain holes" next time you're in there.
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>>Have a look what's down those "drain holes" next time you're in there.
I take it you mean the "drain holes" with a pushrod sticking out of them!
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Hi,
Interesting. I take it thats why Claude has recommended an engine oil addative to clear the gunk? Will I see the drain holes with the rocker cover off? (was planning to remove cover and clean as much gunk out as possible)
Any recommendations of addative? Halfords do Wynns Engine Flush (£5) - any good????
How do I use it? In with the new oil, or in with the old for a bit, then flushed out?
>Update !
Fiesta is much, much happier now. No more blue smoke and not cutting out at idle (had a new ICV too) - its still a little lumpy occasionally but i'll see how that goes. Going to flush and change the oil & filter next wednesday - doing a car course and have access to the workshop - so ideal oppertunity!
Cheers all,
James
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In with the old-run it for about 30 mins.before you drain;if your vehicle is fitted with the seperate crankcase ventilation device(plugs into base of air cleaner)it's worthwhile buying a new one than attempting to clean it out.If it is the type built into the air cleaner,make sure the orifice is clean-they tend to get clogged up and either replace the filter gauze or wash it out very,very thoroughly.
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Hey
already changed the PCV filter to great results.
After reading - www.carbibles.com/additives.html - and others - I think I will stick to just an oil change and maybe another one next year. I will clean what I can out of under the rocker cover....
James
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Hi James
No I didnt mean flushing using an additive. The flushing oil I am referring to is the traditional light oil such as 'Flush Out' made by Comma: www.commaoil.com/
I've found most local motor shops sell that or something similar.
You drain your existing oil, put the sump plug back in, pour in some flushing oil (about a third normal capacity), run engine at idle for say 10 minutes and then drain. Then fill up with new oil.
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Ah - sorry - my mistake then.
Great advice!
Cheers again,
James
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Most "flushing" oils are are standard engine oil plus paraffin.
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This might have been the case in the 1950s-1960s but not now. For one thing, flushing oils are very thin monograde oils (approximating to a straight SAE 5) rather than multigrades. Thinning a multigrade with paraffin will not turn it into a monograde. In fact the characteristics of a multigrade are just what you dont want in a flushing oil which is to be used in an engine running at idle with no load for a very short period.
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All,
An update - to close the story!
Success! The Fieasco has been running well since changing the PCV filter. No blue smoke! I changed the rocker gasket, set the valve clearances and cleaned the rocker cover at the weekend. All good stuff. The rocker cover had the yellow mayonaise on the top only - the valves and gear were all fine.
Just a Oil change & flush to go (Wednesday!)
Thanks,
James
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I wouldn't bother with the flush. A good oil, changed regularly is sufficient.
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I've always flushed a "new to me" secondhand car-because I don't know it's history-then regular changes.
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I've got the comma oil now - so will flush. Not sure of its service-history so sounds like a good plan.
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I've never flushed any of my cars.
I've flushed cars when customers insisted.
I've seen a colleague** have to rebuild his previously good engine after flushing. It suddenly began to burn oil in huge quantities.
** I couldn't resist a laugh, because the guy was a fool in many other respects too. He had carefully saved up the flushing mixture, after not puring the full amount into cusitmers cars, so, he got the flush for free - but the pitons, rings, and gasket set cost him dear!
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Clearly his engine was not 'a previously good engine' at all. The fact that the use of flushing oil apparently led to engine failure only serves to emphasise that its integrity was largely provided by gunge!! Which is no integrity at all. It sounds as if he had a poor engine with a poor maintenance history.
Like many people I dont believe the use of flushing oil is justified in a well maintained engine compared to just a normal oil change. However I have found that the HCS/Enduro engine, which is very prone to contamination with emulsified oil deposits, benefits from the use of a flush out, particularly where oil changes have not been carried out at recommended intervals.
By 'recommended intervals' I mean that all Ford driver booklets highlight the need for more frequent oil changes when making short journeys but most people still stick to mileage intervals. Its hard enough to persuade people to make a yearly oil change when, as far as they are concerned, they only drive to the station every day and have not covered more than 2500 miles in a year. The reality is that they should consider doing an oil change at 6 monthly intervals. But for those that dont, a flush out can help recover the situation and maintain engine performance.
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>>Clearly his engine was not 'a previously good engine' at all.
It had been running well as his family car for a few years before he used the flush - afterwards, it didn't run very well at all. Whatever the mechanism, he would have been better off had he not flushed the engine.
Is engine flushing called up in any manufacturers service schedule?
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If an engine is badly sludged up internally, (I'm talking about thick semi hard deposits, and not mayonase.) I would not recommend a flush. Either strip the engine down and clean it properly, or leave well alone and get rid of the car ASAP.
I have seen it several times were an oil flush on a heavily contaninated engine has caused the deposits to come of in chunks, fouling the oil strainer, and causing oil pressure loss and therefore engine failure. normally this has occured within a month of the oil flush.
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Well now I am confused.
As far as I know the engine is OK inside - but the history is mostly un-known.
There was some mayonaise in the rocker cover only.
James
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>>I dont believe the use of flushing oil is justified in a well maintained engine compared to just a normal oil change.
Actually, I think these are the only engines in which it is safe to carry out a flush. It also happens that these are the engines that don't need to be cleaned out.
Carp on rockers, and rocker covers, etc., is perfectly harmless until it is dislodged.
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ok. Changed the oil - no flushing last night. All appears well.
Ta all,
James
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Hey
already changed the PCV filter to great results.
After reading - Best Oil Additives - and others - I think I will stick to just an oil change and maybe another one next year. I will clean what I can out of under the rocker cover....
James
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You've never heard of a wet and dry compression test? If a dry compression test shows low compression on a cylinder/s then adding a little oil to that cylinder and retesting shows if the compression loss is due to a valve or piston/rings.
When the oil is added if it is a problem with a piston/ring sealing then the compression will rise as the oil is filling the gap.
Engine oil flush does more harm than good, there is plenty to be read about its disadvantages, here's an example..
www.nordicgroup.us/oil.htm
Edited by tldevelopments on 13/12/2008 at 18:29
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I really hadn't - but then I am a novice with a lot of this...
Agree on the disadvantages - a full stripdown and clean would do a better job. As you can see from the last post - it just got a std oil change.
Update :- Change the O2 sensor a few days ago. Cured it's stalling and stuttering - the old one looked like a fouled plug (black!). The theory behind that was the oil that was being sucked through to the exhaust had fouled the O2 sensor - seems a good guess!
Car is running very sweetly now - and I shall be interested to see if the combination of bits (its had a lot of work!) raises the MPG above 27!
Thanks again to all for your help!
James
PS - what should a "used" but "working" O2 sensor look like anyway?
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so to complete this thread. MPG now ~~ 40mpg
Did a dry compression test yesterday. In cylinder order (1-4): 220, 220, 225, 225 PSI
Car had a decent run to Basingstoke->Oxford and back (70miles) - in horizontal driving rain and gales. Performed perfectly and cruised happily at ~~80mph
Cheers all
james
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