Is it time to let go of my 4.0?
#1
02-15-2006, 08:52 PM
Join Date: Feb 2006
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Is it time to let go of my 4.0?
I have a 1997 ford explorer sport V6 4.0 sohc... I bought this truck when it had 28,000 miles, and at 38,000 miles I had the recall done for the nortorious timing chain noise... Well the truck has run great all this time, and has 148,000 miles on it now... Well last week it started making a loud knocking noise... When you first start the truck when it's cold it makes no noise at all... But when it warms up is when it starts to knock loud... I took it in to the mechanic and he changed the chain tensioner, thinking this would solve the problem, but it didn't... The weird thing is that it only does it when it warms up... And if you keep the idle at 1700 rpm's it runs nice and quiet then too... But at any rpm range below or above 1700 rpm's it knocks violently... unlike the ticking noise the timing chain problem before, this is more of a loud knock... The sound seems to be coming from the front/right side of the motor, more towards the top by the intake... Does anyone have any suggestions? After all I've read about the 4.0 engine I think it is time for a new truck, but I can't sell this one like this... Thanks for your help...
#2
02-16-2006, 06:52 AM
#3
02-16-2006, 09:36 AM
Did the mechanic hear the noise when he changed the tensioner? If so, what did he think?
The symptoms you describe sound like rod knock. When the oil is cold it's thicker and will cause it to have better oil pressure which can mask the sounds, but as the engine heats up the oil thins and the pressure drops, and it can make that noise.
You might try putting a real mechanical oil pressure gauge on it to get a better idea of what your oil pressure is doing. The Ford factory O/P gauge is actaully a sort of an idiot light with a needle. As long as the sensor reads oil pressure from the engine above something like 7 psi it sends the needle on the gauge up into the normal range. A mechanical gauge will give you a true reading, and you'll probably find the warm pressure is very low at idle and only in the 20-30 psi range at highway speeds.
If this is the case, don't wirte the truck off just yet. If you like the truck otherwise, why not go through the motor and hang on to it? Or, you could always put a junkyard engine in it and keep going.
Might be a good opportunity for a V8 swap as well.
Or, you could just cut your losses and sell it as a mechanic's special with the understanding that it needs work.
The symptoms you describe sound like rod knock. When the oil is cold it's thicker and will cause it to have better oil pressure which can mask the sounds, but as the engine heats up the oil thins and the pressure drops, and it can make that noise.
You might try putting a real mechanical oil pressure gauge on it to get a better idea of what your oil pressure is doing. The Ford factory O/P gauge is actaully a sort of an idiot light with a needle. As long as the sensor reads oil pressure from the engine above something like 7 psi it sends the needle on the gauge up into the normal range. A mechanical gauge will give you a true reading, and you'll probably find the warm pressure is very low at idle and only in the 20-30 psi range at highway speeds.
If this is the case, don't wirte the truck off just yet. If you like the truck otherwise, why not go through the motor and hang on to it? Or, you could always put a junkyard engine in it and keep going.
Might be a good opportunity for a V8 swap as well.
Or, you could just cut your losses and sell it as a mechanic's special with the understanding that it needs work.