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Cold engine knock
02-05-2009, 09:48 PM
Recently returned from a 2000 mile round trip down south. I am now back in NY and it has been realy cold.
I have noticed that I have what sounds to me like a rod knock when the engine is started cold, it sounds like a single rod and almost goes away after about 3 miles of driving. Never heard it while down south, only in cold NY.
I had changed the oil and filter before the trip and changed it about a week ago hoping it would help but it did not. I have checked the oil pressure and have 55 to 60psi on a cold start, it drops to 20 psi hot and in gear.
The engine has 112000 miles and may have had coolent in the oil twice about 2 years ago. Once from the timing cover gasket and again from the lower intake gasket. Oil was never milky but may have been contaminated, oil was changed several times after the gasket replacments and it has not used any coolant since.
From my old junker driving days I have heard rod knocks but usuly when hot when the oil is thin, not cold like mine is doing. Could this be piston slap and not a rod knock, I could see piston slap going away as the piston warms up and expands. I cannot see a rod bearing warming in 3 miles and tightning up as in 3 miles the oil is still cold.
I do remember reading about someone who droped the pan and replaced the bearings (said they where in bad shape) but were they noisy ?? cannot find the post now
Vehicle info 96 Windstar 3.8 with 112000 miles
02-06-2009, 08:48 PM
Hey I have a 98 3.8 windstar with 210,XXX miles on it with the same exact problem.....I too live in NY and it has been very cold latley and whenever I start the van in the morinig you can hear a faint knock. Although mine does it constantly its louder when it is cold.
I run 20w50 oil however because if I dont the oil pressure indicator flickers when it is idleing in drive.
I know it is about at the end of its useful life but it has been very reliable for both me and my parents (they bought it brand new) and I will continue to drive it untill it dies then start on another project lol.
02-06-2009, 11:31 PM
How long has yours been knocking? I am still using 10-30 or 10-40 oil and have good oil pressure. It's at 112000 miles now and want to keep it a while longer. If I could find someone who had the same problem and cured it by droping the pan and replacing bearings I would do it.
If it holds out till warmer weather I may do it anyway, while I am at it I will replace the pan also. It has some real bad rust spots on it and I have been keeping it covered in gear grease to slow the spread of rust.
Got to love the NY weather and the road salt.
02-07-2009, 09:15 AM
I vote for "piston slap" .. if it goes silent with temperature rise.
I have disassembled 4 cyls that had piston slap .. and the crank and bearings be nearly wear-free. Piston slap is aggravated by the rings being trapped in their grooves by sludge ... and also by top end carbon build-up causing a little pre-ignition.
There is no remedy, other than disassembly and cleaning piston tops ...and ring grooves and cyl heads. Of course, if there is excessive cyl wear ... you will also need an overbore and new pistons.
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