hello all,

i just bought my 95 classic swb and am concerned about a knock in the engine. i didn't notice the knock when i bought the truck but there was a rather loud exhaust leak that may have prevented me from hearing it (pipe was completely separated between flange and front muffler, i've done a temp. patch). there are only 60000 mi on the clock and the fluid levels are good. there is no noise until the engine is up to temp., then the knock starts. it sounds like it is coming from the lower engine (sounds the loudest with the stephoscope against the oil pan). as rpm's increase the frequency, but not volume, of knock increases. i'd appreciate any ideas on the matter. i'd like to know what i might be up against.

thanks a lot,

trevor

 

I would suggest you do an ATF flush and clean out the engine, should help.
Go buy 6 quarts of any ATF, drain the engine, replace the oil with the ATF, let it idle for 20 minutes then do a regular oil change.
Use only Mobil 1 or K&N 3001 oil filters.

 

Sounds like one of your bearings are gone. Wish had better news.

Flushing the engine will make it louder.

James

 

Yeah, sounds like bottom end. The good news is you can replace them from below and without removing half the engine.

 

Yes, it may make them louder, or not. If it does and you need bearings, it will be a cleaner job and the engine should be flushed out anyway. If it doesn't then it may correct a potential problem, even if for only a couple thousand miles till you are ready to work on it.

 

thanks for the input. i had my dad's friend (he's a retired mechanic) listen to it today. he said it doesn't sound like bearings because when you rev the engine it doesn't get any louder (you actually can't hear it at all with the engine revved). does this sound right? he questioned the oil pressure. the oil light isn't on, but we noticed that it doesn't light up when you turn the key. he said to pull the wire on the oil sending unit and short it to ground, said that should make the light come on. i did this and nothing. i pulled the instrument panel and checked the bulb which is fine. any ideas on this?

i'm still thinking about the engine flush. i know there are some varying opinions on this. i'm a bit concerned about clogging up the oil pump. if i do a flush is it best to pull the pan and clean it out? i guess i could check the bearings then.

Mike- thanks for the advice on filters,what weight/brand oil do you recommend?

thanks again everyone,

trevor

 

Trevor,
Look at the flush this way, it will safely clean out the engine, if it were to plug up the intake tube, then it is so bad that a flush is needed and it is no big deal to drop the pan and clean out all the sludge that may or may not come down.
As for the oil, kind f depends on how cold it gets in your area. If you have really cold winters like I do in Colorado, then look at a 5W/30, if you have normal California type winters then a 10W/30 or 10W/40 are fine.
Also, let us know about your oil pressure light and or sender.

 

Not really. A bad bearing can be simply a very minor scratch or surface scuff on one of the shells..and that will not make more noise as you rev as the extra sound will make it harder to hear.

However, you are concerned about oil pressure that MUST be checked. Your oil pump has a number of unused threaded holes now occupied by plugs. Additionally, you have your oil pressure warning light. In one of these places, thread in a pressure gauge. If you need an adapter, any auto or plumbing store will have the one you need for a couple of dollars.

Start up the engine and check your pressure. It will not be too high at idle after warm up as these engines rely on high volume rather than high pressure. Let's see what you get.

Lifters for ALL these engines were made for 20W50 oil. However, you can use a bit lower than that.
The sad thing is that these are flat tappet engines (one of the last) and need the additive that was used in all engine oils until recently. It is called ZDDP.

Since 2004, the oil companies have been reducing the amount of zddp without indicating that. The lack of it has sent many new engines and new tappet/camshaft combos back with significant damage on during the 500-800 mile break-in period.

The aftermarket camshaft makers are fighting that by recommending the bottled zddp the provide with their new lifters and cams. If you don't use it with a flat tappet engine, that will void their warranty on the cam.

On the happier side, there is no evidence as yet on damage to engines that are already bedded in successfully. However, it is prudent to use oils that still have sufficently high zddp levels. The ones you suggest do not.

Try a 15W40. That's a diesel motor oil made for non-cat engines..they will have the old levels for a while (until the new legislation forces them to have cats as well). Specialty racing oils also still have high levels and some of the 20W50s. Cosworth Racing, Shell Rotella T 15W40, Penzoil 20W-50W Racing and Quaker State Q Racing. However, this issue a moving target and the movement is ever downward with no advisories being made. http://www.vscda.org/TechInfo/Bulletin4.pdf
or simply google "zddp".

If the oil pressure turns out to be fine. I would be interested to know what oil Trevor has been using and what happens to his "knock" if he adds 4 oz of zddp. http://www.zddplus.com/

James

 

hello again,

let me start by saying thanks. i appreciateyour patience and helpfullness, i know i have a lot to learn.

as for the light/sender, after fashioning a pressure gauge set-up that could be threaded into the oil sending unit tapping (if anyone else does this, it may be helpful to know that the sender tapping is 1/2" -20 thread, no matter how certain the guy at the auto parts store is that it is 1/4" npt. i'd hate to see someone turn a 1/4 fitting in there), i was able to read the oil pressure. i've only read it at cold idle, but it was between 30 and 32 psi, which doesn't seem that low to me. please let me know if i'm wrong.

i've only had the truck for about three weeks and have driven maybe 200 mi. i did an oil change about a week ago and used napa 5w30. the previous owner had it serviced by the lr dealer. i believe they used castrol 15w40.

still haven't added or flushed anything yet.

thanks again,

trevor

 

Well done Trevor. You have eliminated the lack of oil pressure as a possibility. 32 psi at idle with cold oil is good..(It will go lower as the oil warms up)

If so, the dealer was apparently aware of the zddp issue and tappet requirements or he would not have used a thicker diesel motor oil. Best thing thing for these engines motor oil wise is frequent changes with a mineral oil that still contains a sufficient amount of the traditional additives.

Have you taken the cylinder pressures? That could eliminate a number of other possibilites as well.

James