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Low oil light @ idle and timing chain noise

98EdBomber

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98 4.0 SOHC 165K miles

Recently had timing chain guides fixed. No sludge build up at all when i dropped oil pan and removed valve cover to set timing. Also inspected oil pickup tube and it appeared to be fine but I shot it with carb cleaner anyways. Didnt seem to bad. Not sure if its clogged but i doubt it because i have normal pressure at normal driving speed. Changed oil/filter (motorcraft).

Went with a thicker oil and lucas additive as I could tell there wasnt enough pressure on the tensioner and making the camshaft chain rattle.The thicker oil helped quiet it down for about a month or so but now its back. Also changed the sending unit but I can tell that this wasnt the issue because of the chain rattle.

Its only at warm idle. Drives fine otherwise and no other issues and no chain rattle heard or knocking heard as well (that I can tell anyways). No knocking heard either AT IDLE but I havent used a stethescope. Just the slight chain rattle. Its definitely the left side cam chain as i am very familiar with this sound. The rear is quiet. Oil level is good. Only happens at stop lights or at warm idle. Why could I be losing oil pressure at idle?

Any ideas what could be going on?
 


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koda2000

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one more time... your engine spins the oil pump. the faster you spin the engine, the higher the oil pressure. oil is thicker when cold. once your engine heats up, your oil becomes much thinner. the thinner the oil, the lower the oil pressure. you've checked all the possible inexpensive/easy things and found them not to be the problem. the only conclusion is that your bearings are worn (crankshaft and/or cam shaft bearings). when this happens the oil pressure drops because the gap between the bearing and the shaft is increased and does not resist the oil flow (especially when hot). with thicker oils you can keep the oil pressure up higher, but only for so long. you engine is basically worn out. is it worth rebuilding? probably not. rebuilding it yourself can save you some money, but it's a ton of labor, special tools are required, not to mention special skills, and the results are questionable. paying for a rebuild will cost you more than the truck is worth. buying a remanufactured engine will cost you more than the truck is worth. another member just posted that he spent $3,500 having someone rebuild his engine and he's having trouble with it. the choice (and dollars) are yours. i'd look for another vehicle (JMO).

edit: one last fairly inexpensive thing you can try is replacing the oil pump.
 




my98nnj

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Good info, but at only 165K if the maintenance (oil changes) were kept up, I can't imagine that much bearing wear could happen??? I'd give the oil pump replacement a shot first.
 




SoNic67

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I would suggest a high volume oil pump - if you go that route. Some people can replace the crank bearings while the pan is off, but that's a lot more work.

You are lucky that you have a 2WD, on 4x4 or AWD the oil pan is blocked by front end components.
 




98EdBomber

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Good info, but at only 165K if the maintenance (oil changes) were kept up, I can't imagine that much bearing wear could happen??? I'd give the oil pump replacement a shot first.

Oil changes every 3-5k since i bought it when it had 10K on it. Normal sediment in pan when i removed it. But Id imagine it would have pressure issues while driving at speed if the pump was failing would it not?
 




koda2000

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Oil changes every 3-5k since i bought it when it had 10K on it. Normal sediment in pan when i removed it. But Id imagine it would have pressure issues while driving at speed if the pump was failing would it not?

at driving speed the pump is turning much faster than it is at idle. the general rule of thumb for decent oil pressure is 10 psi for every 1000 rpm up to around 40 psi. the oil pump consists of 2 gear/impeller looking things which spin in a cavity. one of the impellers is driven by the engine, in turn it then drives the other one, squeezing the oil between them (that's what makes the pressure). when new, the tolerances on the pump are very close. with age (165k is no spring chicken for a 4.0L SOHC, even with regular oil changes) the impellers wear down the cavity they spin in, which allows pressure to be lost. it's the same principle as with the engine bearings, too much clearance = less oil pressure, which is particularly noticeable at low engine speed when the oil is hot/thin.

if you really need/want to get more miles out of this vehicle, try replacing the oil pump. maybe you'll get lucky. good luck and let us know how it turns out.
 




Bobmbx

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When you had the timing chain "fixed", was any of the plastic guide missing? If so, you may have a small piece stuck in the oil pump relief valve holding it open. At low RPM, you may be losing your pressure at the relief valve. At higher RPMs, the relief valve would be wide open anyway because there is much more oil flowing.

My 02 Sport Trac chain guides failed at 241k, and took out the oil pump with all the small pieces floating around the system.
 




98EdBomber

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When you had the timing chain "fixed", was any of the plastic guide missing? If so, you may have a small piece stuck in the oil pump relief valve holding it open. At low RPM, you may be losing your pressure at the relief valve. At higher RPMs, the relief valve would be wide open anyway because there is much more oil flowing.

My 02 Sport Trac chain guides failed at 241k, and took out the oil pump with all the small pieces floating around the system.

Yes there were pieces in the lower pan and also in the pick up screen. I was sure to remove all of those fragments. But heres what I did. After the repair, I put in regular (non synthetic) new Mobile 1 5W-30 w/filter (motorcraft) which Ive always used since day one and the chain started rattling like crazy and the oil pressure was very low at idle. So I went with Penzoil "High mileage" 10w-40 with lucas. It immediately quieted down and pressure was back up for about two months. Everything seemed ok. Not much power loss but as i assumed, there was about 3mpg loss which im fine with. Cold starts were doing ok as its been over 100F here. No weird noises/knocking.

Now the problem is back and the chain is rattling again (at hot idle) - not while driving, and the light came back on which means less than 6-7psi at idle. Not sure about the pressure when driving. I dont have any weird knocking or pinging. No sludge in the engine at all.

But I also realize FLOW is better than pressure so here what im thinking... go back to a synthetic oil but Im not sure whats the heaviest I should go with? If the pump is bad and I went with a 5w-40 its still going to create less FLOW but more pressure perhaps, which might not be ideal. The synthetic may help lubricate and flow better im assuming. If the oil spring was stuck, why did it not have these symptoms right away after i put the 10w-40 in? Should I go back to a 5w to help cold start oil flow and just deal with the low pressure until new oil pump - and maybe the synthetic will help too?

Whatya think here?
 




SoNic67

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First of all - you have two threads open for the same issue. Annoying.

Second: Flow means nothing, it's just a urban legend. For example, water would flow the best, but it won't help keeping your engine steel parts separated.
Oil needs to create a film between the surfaces, film that has a porting effect. And that film is dependent only of the static pressure in the respective interstitial space.

5W helps with cold starts, even at 90-100F outside temperatures.

Synthetic oils use limited (or none for Mobile 1 'Extended Performance' and Amsoil) VI additives and that's why they 'keep' their grade longer. The 10W-40 normal oil that you used has that range because of heavy use of VI additives. When those wear out, you remain with a 10W-10 oil...
So... you have wear out your oil already. Change it or switch to a better oil.
 




98EdBomber

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First of all - you have two threads open for the same issue. Annoying.

Second: Flow means nothing, it's just a urban legend. For example, water would flow the best, but it won't help keeping your engine steel parts separated.
Oil needs to create a film between the surfaces, film that has a porting effect. And that film is dependent only of the static pressure in the respective interstitial space.

5W helps with cold starts, even at 90-100F outside temperatures. Synthetic oils use limited (or none for Mobile 1 Extended performance and Amsoil) VI additives and that's why they 'keep' their grade longer. The 10W-40 normal oil that you used has that range because of heavy use of VI additives. When those wear out, you remain with a 10W-10 oil...

Yea i know. My bad. I will delete it if I can.Thanks for the replies..
 




koda2000

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oil flow is unimportant. pressure is everything in regard to the crankshaft and cam bearings (as well as the hydraulic chain tensioners).

if it's 100F out, I don't know why you insist on using multi-viscosity oils. try using a straight 40 or even 50 weight while it's summer. I've always found that multi-viscosity oils (regardless of weight) get as thin as mouse piss once hot. the 5w isn't even coming into play at 100F. I've mentioned this before.

you're in major denial. there's is something seriously wrong with your engine. maybe it's the oil pump, or maybe your bearings are wiped. you might as well try the cheapest/easiest fix (replace the oil pump) and see if it helps, or just run thicker oil and drive it into the ground. if a piece of debris has gotten into the pump, causing even a small scratch on the pumps inner surface, it can cause a pressure drop.

I don't see where there's any point in discussing this further. it's been months and you're about out of options. there's no magic pill and, as the condition is getting worse, you're living on borrowed time. if you don't want to try replacing the pump the only other thing you can do is use thicker oil.
 




98EdBomber

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oil flow is unimportant. pressure is everything in regard to the crankshaft and cam bearings (as well as the hydraulic chain tensioners).

if it's 100F out, I don't know why you insist on using multi-viscosity oils. try using a straight 40 or even 50 weight while it's summer. I've always found that multi-viscosity oils (regardless of weight) get as thin as mouse piss once hot. the 5w isn't even coming into play at 100F. I've mentioned this before.

you're in major denial. there's is something seriously wrong with your engine. maybe it's the oil pump, or maybe your bearings are wiped. you might as well try the cheapest/easiest fix (replace the oil pump) and see if it helps, or just run thicker oil and drive it into the ground. if a piece of debris has gotten into the pump, causing even a small scratch on the pumps inner surface, it can cause a pressure drop.

I don't see where there's any point in discussing this further. it's been months and you're about out of options. there's no magic pill and, as the condition is getting worse, you're living on borrowed time. if you don't want to try replacing the pump the only other thing you can do is use thicker oil.


Its not a daily driver so thats why its been months and Im still wondering what to do with it so Im in no hurry. I appreciate all of your help and will go with your suggestion to do the oil pump as this seems to be the cheapest thing to do at this time. So SAE 40 or 50 it is.

I will report back with the outcome. Now dealing with that upper pan is going to fun! Its a 2WD so Im hoping it should drop out with no issues. If you have any advice/tips on the removal Id like to hear, but if not thats fine as I can sense your irritation. ;)..

Thank you for your patience and time with me. Cheers!
 




SoNic67

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2WD might be easier. I had to pay somebody $400 - drop the whole front end on my AWD to replace the pump (and pump pick-up, shaft). And even then, the steering rack was too close of the pan, he needed to remove engine mounts and raise it a few inches.
Probably that lead latter to my exhaust gaskets leaking...
 




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