Omega Owners Forum
Omega Help Area => Omega General Help => Topic started by: ScottieMV6 on 05 August 2009, 17:30:07
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Just done the oil cooler (albeit the replacement was used - a very low mileage one off a member on here). Been out today and did about 10 miles before the car started misfiring, belching out clouds of white smoke and smelling very nasty.
I'm thinking oil cooler again or head gasket. I know head gasket is very rare but there doesn't seem to be the brown sludge in the header tank that I had last time.
Done paperclip and the only fault is with the SAI system.
Any thoughts? :( :( :(
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Sounds similar to mine - I did the oil cooler, it ticked over fine, ran OK for a bit... but my HG is definitely a goner. As evidenced by clouds of white smoke, and, er, a nasty smell...
Get an exhaust gas sniffer on the job, and have a look for bubbling in the expansion tank when you rev it by hand.
HTH :y
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Thanks Pete
I would have a look but I really don't want to run it if I can help it.
Is there anyway to get a definitive answer whether its the HG?
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When the oil cooler failed and presumably the car started over heating...did you continue to use the car??
Headgasket failure on the v6 is generally caused by continued use when over heating as a result of an alternative failure such as oil cooler or water pump...
Symptoms definitely sound like HG though...is there mayo looking stuff on your dipstick too??
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White smoke = water, Blue= oil. sound like HG.
you could try a compression test and see if that gives you any clues ie which side is knackerd, but it is better to change both.
Have you checked what coulor your plugs are? or if they are wet?
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Headgasket failure on the v6 is generally caused by continued use when over heating as a result of an alternative failure such as oil cooler or water pump...
*nods sagely*
Though mine didn't show as overheating on the temp gauge, it was using coolant. Bed, made, lie in it, etc. :-[
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When the oil cooler failed I stopped using the car straight away and there were no signs of overheating.
There is no mayo on the dipstick but there is in the filler neck (not loads though).
I guess I'll have to go and get a compression tester and see what the results of that are. Anyone tell me what the compression should be?
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Anyone tell me what the compression should be?
At a guess, 12-14 BAR. More important are the relative readings. Sounds like it was a fairly dramatic failure so it should be obvious that one or two cylinders are way down.
Kevin
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You can work out a theoretical compression pressure (for a perfect engine) by multiplying atmospheric pressure by the compression ratio.
If your engine has a 10 to 1 compression ratio the theoretical pressure would be 10 * 14.7 psi = 147 psi. This is an absolute pressure (the difference between it and a vacuum). For gauge pressure you have to subtract atmospheric pressure ie 147 - 14.7 = 132.3 psi.
If you use a gauge with Bar on it the maths is simpler because 1 Bar is very close to atmospheric pressure ie 10 * 1 Bar = 10 Bar absolute or 9 Bar gauge.
Because the gauge has a rubber hose you lose some of the compression ratio due to the volume of air in the pipe so you will never see the theoretical pressure.
The key is the difference in pressures between individual cylinders. I think rule of thumb is that anything over 10% variation is bad news. With the symptoms you have described I would expect most of the cylinders to be around 120psi/8Bar and one below 75psi/5Bar.
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Caveat: I used 10:1 as an example. The last engine I used my compression tester on was my old Land Rover which may have started out at 8.5 to 1 but was very well worn.
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Oops, it is more complicated than I thought. Air gets hot when it is compressed which raises the pressure.
These people http://www.pumaracing.co.uk/comp.htm give a better explanation.
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It also depends how strongly it's turning over on the starter. As said, it's the relative readings that are important, because a major mechanical issue such as this won't affect all cylinders equally.
Kevin
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Thanks Andy
I am going to buy a compression tester and see what results I get.
Can anyone tell me if I am right in thinking that I need one with a 10mm adapter on the end?
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I think Kevin has given you the correct numbers (12-14 bar). The figures I came up with would be more appropriate for a worn out, Land Rover with cart springs.
Not sure about the spark plug thread, you will be taking them out anyway so I would take one with me to the shop to be sure.
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I would do that Andy but I have seen this http://www.amazon.co.uk/exec/obidos/ASIN/B0002BUU0C/ref=ord_cart_shr?_encoding=UTF8&m=AJ165RZ9PUVHQ and it is a lot cheaper than they are in the shops.
Also I assume that I need the engine relatively intact when I do the test. Can I remove the plenum etc or do I have to do it with everything still in place?
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Just out of curiosity I topped up the coolant and started the car up today with the cap off the header tank.
No misfire but lots of white smoke and lots of bubbles coming up out of the header tank.
Does this mean anything/give any more clues?
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If the bubbles appear to be more than just the system purging air out, and appear right from cold, it does sound like a head gasket symptom. :-/
Kevin
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They appear right away as soon as I started it up and there were a lot of them constantly.
Kev - do you know if the compression tester I need is 10mm thread?
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They appear right away as soon as I started it up and there were a lot of them constantly.
Kev - do you know if the compression tester I need is 10mm thread?
The thread size is 14mm, which is by far the most common. Something like a Gunson Hi-Gauge, or most compression testers, will have this thread as standard without the need for an adaptor, I'm sure.
What I have had to do in the past is add a long reach adaptor for engines where the plug threads are deeply recessed in the wells, but I'm not sure if you'd need one for a V6.
Kevin
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I think (but await someone more knowledgeable than I) that you could disconnect the fuel injection multiplug, and spin it over on the starter with the plenum off. But, as I say, wait for someone to confirm.
If you take the plenum off, and the injection bits, you should be able to feel if any of the cylinders are wet - my no.6 inlet is misted with coolant, for example.
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You don't really want sparks either, I don't know how true it is but I have read that the DIS pack can fail if it the HT leads and plugs aren't fitted & working. The spark has to go somewhere and if it can't discharge via the spark plugs it finds another route.
You can use a remote switch on a lead with a couple of crocodile clips to crank the engine. One clip to the battery 12v terminal on the starter motor, the other clip to the solenoid terminal on the side of starter motor. You can hold the switch in one hand and the gauge in the other. The ignition key stays in your pocket.
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The sympton you've described are everything my car was suffering with and the result is a new HG and £800 missing from my bank account :o
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You don't really want sparks either, I don't know how true it is but I have read that the DIS pack can fail if it the HT leads and plugs aren't fitted & working. The spark has to go somewhere and if it can't discharge via the spark plugs it finds another route.
You can use a remote switch on a lead with a couple of crocodile clips to crank the engine. One clip to the battery 12v terminal on the starter motor, the other clip to the solenoid terminal on the side of starter motor. You can hold the switch in one hand and the gauge in the other. The ignition key stays in your pocket.
You can also remove the two purple relays at the back of the engine bay relay box. No ECU feed and no fuel pump. :y
Kevin