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causes of low cylinder compression in a td42
Posted: Mon Apr 20, 2009 7:21 pm
by patrolla
i've just had a compression test done on the cylinders and it's running factory spec on cylinders 1-4, with slightly below on cylinder 5 and quite a bit below on cylinder 6. has done 320,000km and is an '88 model.
what could be the possible causes or is that asking how long's a piece of string?
Posted: Mon Apr 20, 2009 7:46 pm
by Z()LTAN
Posted: Mon Apr 20, 2009 7:59 pm
by jet-6
2 bent rods
Posted: Mon Apr 20, 2009 8:10 pm
by Z()LTAN
nah mate, the rings on 5-6 are worn out.
Its not uncommon for the rings to wear out non uniformly.
causes of low compression
Posted: Mon Apr 20, 2009 9:01 pm
by busman
Get a leak down test done to see if it's rings or valves or both.
Posted: Tue Apr 21, 2009 10:47 pm
by mavzilla
been through water and bent no 5&6 rod my guess , very common
Posted: Tue Apr 21, 2009 11:03 pm
by Z()LTAN
lol u can tell if its got a bent rod... what with all the clakking and white smoke...
Re: causes of low cylinder compression in a td42
Posted: Tue Apr 21, 2009 11:37 pm
by heathhoppy
patrolla wrote:i've just had a compression test done on the cylinders and it's running factory spec on cylinders 1-4, with slightly below on cylinder 5 and quite a bit below on cylinder 6. has done 320,000km and is an '88 model.
what could be the possible causes or is that asking how long's a piece of string?
maybe worn out had dirty air cleaner services not up to date the list could go on and on
Posted: Wed Apr 22, 2009 11:13 am
by patrolla
so i got the compression readings:
1-4 = 500
5 = 450
6 = 475
apparently those readings are all above spec but 5 and 6 should be a little higher in an ideal world. still no issues turbo-ing on those readings, according to diesel tech in lilydale.
Posted: Wed Apr 22, 2009 12:12 pm
by Z()LTAN
yeah thats not down all that far.
Youll be looking at a ring and bearing kit at some time in the future no doubt.
Posted: Wed Apr 22, 2009 12:41 pm
by WOZ
I would be checking the tappet clearence. Its only down 10% of its compression on those cyls. I get a lot of td42s in my shop that are sluggish until the tappets are adjusted. If you are concerned about engine condition, have a proper leak-down test done, if its about 20% or less the engine is fine. Hope this helps.
Posted: Wed Apr 22, 2009 1:54 pm
by patrolla
yeah, my mechanic (who's not a diesel specialist but still pretty good) said it is a bit "tappety".....considering the ring and valve leak tests as well as tappet adjustment.
Posted: Wed Apr 22, 2009 8:13 pm
by PGS 4WD
If the cylinders are side by side (5&6) it is common for the head gasket to blow between cylinders, it could be tight valves, worn rings, bent rods and all the ther mentioned things too.
Joel
Posted: Thu Apr 23, 2009 9:14 am
by patrolla
but if it's not using any water, it wouldn't be head gaskets would it? and what if it did use a small amount of water, hypothetically?
Posted: Sun Apr 26, 2009 10:42 pm
by Troll00
My GU with 290k on the clock had 180 in #2 and 380 in some and the best was 450, had a cracked head stuffed bores, pistions, rings etc etc
Still doing the rebuild
