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Oddmodman

Sludge Causing Knock?

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Hey guys, I have a 1990 Jeep Cherokee Sport, 4x4, 4.0, 5spd that has a light knock. Its crankcase breather thingie was rotten so I got a new one and installed it, and when I did I noticed that inside at that point, there was a serious buildup of sludge. Looked like someone took some rubber and oil and blended them together and poured it in. How might I get rid of this? Pour seafoam in that hole? In the oil? Will it actually get high enough to clean that out? And last, even if it does get up in there and cleans it out, I'm seriously worried about it doing more damage to the engine than it's worth. And last last, after all this should I switch to 15w40 diesel oil to help that knock?

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If the sludge is as bad as you say.......

 

Break up that sludge and it will go to the pan where it will get sucked up into the oil pick-up stainer and starve the pump.......I give your 4.0 two days before it's fried.

 

 

Pull the valve cover and physically clean it off, suck it up with a ShopVac, stuff holes with rags to keep it out of the bottom. Remove oil pan and clean it out, same with pump pick-up.

 

That said.....you already have a knock.........so............

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If I were in your shoes.....

 

Find your casting #s on the head or model and year, call around to head exchange/rebuilders for the cost of a rebuilt head. If time is not of the essence, pull your head and have it cleaned, valves done, decked. Either way will cost you about $250.

While it is running (as in now) pull one spark plug wire at a time, determine what cylinder has the knock, if the knock goes away or sounds different when you pull plug wire for cylinder #3, that is the cylinder with the knock.

Install new head, pull pan and clean, replace rod bearing.

This will cost you about $400, gaskets, head work, oil, coolant, and can be done on a weekend.

 

Worst case....you get another 10K miles out of it.

 

 

Option two, rebuild or save money for rebuilt engine while this one is still running.

 

Option three, while this one is still running, look for a donor. Look to a same year Cherokee with bad trans, wrecked, rust bucket, or generally unwanted. One that you can pick up and drag home for $500 but otherwise runs great...you are looking for a good engine. Get a buddy to help you and swap on a weekend. Haul donor to the scrap yard and get $400 of your money back. Oil, coolant...etc....plus a loss on donor........swap may cost you $200 or so.

Take 50 different pics of your engine bay from 50 different angles.......this way you will know what wire....what hose....what vacuum line....went where.

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I posted this before.....You could try this.....it has worked for me....it might help you get a few more miles out of the motor without putting big money out

 

(As per you first post....get a new pcv valve....don't just clean it)

 

Dr. YXMJ’s Oil Wash…

There are 2 ways 2 do this the quick way and the extreme (right) way…

  1. Quick Way Go to your low budget auto supply store (Walmart??) and buy the cheapest motor oil and filter you can find. Also buy a high quality (I run 10W30 synthetic oil and filter)
  2. Go home and check your oil…..I would assume it is down ½ -1 quart
  3. Add (here is where different recipes come into play) your choice to top up….ATF….Sea-foam (my favorite)…..Diesel fuel….
  4. Run the truck up to operating temp shut off and safely and carefully change the oil as usual.
  5. Change to cheap filter and add cheap oil…….(here is where some more sea-form is nice).
  6. Go for a drive or run the motor for 20 min.
  7. Shut off and safely and carefully change the oil as usual.
  8. Now add the good oil(10w30) with a new good filter……..Did that solve it?

 

  1. Extreme Way Go to your low budget auto supply store (Wal-mart??) and buy 2 complete changes of the cheapest motor oil and  2 filters you can find.
  2. Go home and check your oil…..I would assume it is down ½ -1 quart
  3. Add (here is where different recipes come into play) your choice to top up….ATF….Sea-foam…..Diesel fuel….(I love the sea-foam)
  4. Run the truck up to operating temp shut off and safely and carefully change the oil as usual.
  5. Change to cheap filter and add cheap oil…….(here is where some more sea-form is nice).
  6. Go for a drive or run the motor for 20 min.
  7. Shut off and safely and carefully Drain the oil
  8. Now drop the oil-pan and remove the valve cover….take both to your parts washer or a least a tub with some Varsole (you single guys can use the kitchen sink….the married ones know better) and clean both until you are willing to eat eggs out of them. (If you want now is a good time to add some fresh paint).
  9. Replace both with new gaskets or high quality RV silicon.
  10. Change to your second cheap filter and top up with NEW cheap oil.
  11. Drive down to the auto parts store and buy a high quality  (I run 10W30 synthetic) oil and filter. Listen to you motor….is it getting better??
  12. At home drain out that new cheap oil and change the filter to the good one….fill up with the synthetic

I hope this Helps someone out there   :thumbsup:

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Just an addendum to the above: when you run your engine with thinned oil (regardless of what you have added that thins it), you get less lubrication protection from it... thus it's a very good idea to run the engine only under light load and limited speed (RPMs) for limited duration (25-50 miles). Afterwards, the drained oil looks like either Hershey's Chocolate syrup or black roofing tar, depending on the nature of the deposits removed.

 

The fella who taught me the trick (shop owner and former boss back in my youth) said using ATF would not only remove deposits by virtue of the lower viscosity and different additives, but would also liven up old seals to some degree. From the engines I have torn down after having used ATF to clean it before overhauling it, this would seem to be true. Engines so treated have been amazingly clean upon disassembly, with all sludge gone from under the valve cover. Even the piston ring grooves are clean! Rod bearings seem none the worse, still showing babbit... but note that since I never measured them before and after, all I can vouch for is that the bearings did not wear down to copper from the experience.

 

I have used the method I described (adding 1 quart of ATF 50 miles before oil changes) uncounted (probably over 200) times over the last 30 years, and at least 3 times in the same engine with no apparent ill effects. It definitely slowed down oil seal leaks somewhat, presumably by softening the constituent rubber for a while.

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Determine if the knock is due to a bearing, or is it a lifter tick or even possibly an exhaust leak. If it is a rod bearing, there isn't any additive or cleaning that will fix that. I'd start looking for a replacement motor, or plan to rebuild yours.

Does the knock get worse as the engine warms up? If it is a bearing, it should be reasonably quiet when first started, then get louder as the engine warms. Just my .02 cents.

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Determine if the knock is due to a bearing, or is it a lifter tick or even possibly an exhaust leak. If it is a rod bearing, there isn't any additive or cleaning that will fix that. I'd start looking for a replacement motor, or plan to rebuild yours.

Does the knock get worse as the engine warms up? If it is a bearing, it should be reasonably quiet when first started, then get louder as the engine warms. Just my .02 cents.

 

Dead on target to the original post, and the best advice.

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Hey guys, I have a 1990 Jeep Cherokee Sport, 4x4, 4.0, 5spd that has a light knock. Its crankcase breather thingie was rotten so I got a new one and installed it, and when I did I noticed that inside at that point, there was a serious buildup of sludge. Looked like someone took some rubber and oil and blended them together and poured it in. How might I get rid of this? Pour seafoam in that hole? In the oil? Will it actually get high enough to clean that out? And last, even if it does get up in there and cleans it out, I'm seriously worried about it doing more damage to the engine than it's worth. And last last, after all this should I switch to 15w40 diesel oil to help that knock?

 

Myself....I would try spending an hour..... and $20..... on cleaning it up and a couple of fast oil changes to see if that helps first......Before I throw in the towel and start pulling motors...and spending Hundred$   :dunno:

 

And even if it is a worst case sceanero....nobody anywhere is going to tell be that it is a bad thing to change your oil  :thumbsup: it will help whatever is ailing you... . :MJ 2: .

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Ok guys thanks for the help. I was really hoping to sell this thing asap. Originally I bought it for 250 with just under 150k on it, for parts for my comanches. It ran, but poorly. I cleaned the CPS and it ran true, so I figured it was worth registering and tagging to sell it, despite the knock...then I saw this buildup. It seems to only be at the back of the motor. I don't see the buildup when I pull the oil cap. Bummer.

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