Rod knock need to check oil pressure

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dragnet

Well-known member
Dec 23, 2008
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My motor makes a bit of a knock when cold. As the engine warms it goes away. Sometimes completely, sometimes you can barely hear it when driving up hill at low rpms. A buddy of mine thinks it may be a rod bearing going south.

I recently put Castrol 5W40 Syntec in it with the oversized K&N filter. Temp was -20C for a while so I wanted the thinner oil for cold mornings. Temp is back up in the teens now. Could the 5W40 be too thin for the truck or the filter too big? Should I go to a 10W40 or 15W40 and see if the knock persists?

I would like to check the oil pressure. I've read on the forum here that if oil pressure is ok, probably not a problem in the bottom end of the engine. I don't have the RAVE cd handy at the moment. Do I just need the appropriate adapter to bolt into the current oil pressure switch position and then connect the oil pressure gauge to that? Where is the current oil pressure switch located? Off the pump I assume.

I've searched but most posts just say "Have you pressure checked" they don't explain how to do it. Next time I get a chance I'll check out the RAVE at my buddies, but for now I'm flying blind.

A lot of questions here, thanks for you time...
 
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dragnet

Well-known member
Dec 23, 2008
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To be honest, wasn't any worse when real cold. Outside temp doesn't seem to make a difference. Although the knocking inside the cockpit gets louder with my knees knocking together rapidly. :)

Knock is at it's worst when motor cold and under load. Once warm not really any noise unless your really listening for it. At some points after a good 15 min run no noise at all is discernable.

And yes, I checked. Castrol Syntec 5W40 is a3/b3 rated and SJ rated as well, which is what the owners manual specifies...
 
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dragnet

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Dec 23, 2008
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Is spark knock due to weak coils/old plugs/bad leads etc? The truck is due for plugs and leads.

I've already tightened down all the exhaust bolts (manifold and y-pipe). Doesn't sound like an exhaust leak to me, but I know exhaust leaks can take on all forms of noise. I've got new y-pipe gaskets here so I may pop them in just in case.

I would imagine the best course of action is to get an oil pressure reading and perhaps a stethoscope on the bottom end of the block. I just wanted to know if what I am describing could be rod knock? From what I have read on-line bad rod bearings should get worse as the oil warms up, oil pressure decreases and less oil reaches them. Is this true? Should my knock get worse the hotter the motor gets and be less noticeable when the engine is cold?

New to all this internal engine stuff. Quite happy to change my own oil, tires, brakes, suspension, belts, sensors etc. When it comes to internal stuff I shy away. Although I own a Rover now, so it seems I may have to take a crash course on internal combustion engine 101.
 
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dragnet

Well-known member
Dec 23, 2008
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Don't think so. I was wondering about that as well. It's a K&N 3001, the long one. From reading past posts it seemed to be recommended. I'm going to go to a Mobile 1 15W50 today and a smaller filter to see if there is any difference. If not the next step is some carbon cleaner like Seafoam, plugs and leads. If still no difference then perhaps some Marvel Mystery Oil in the crankcase. At that point if the noise persists and I've ruled out all the above plus exhaust leaks I guess it is something more serious and may involve motor replacement. Guess I'll either drive it until it dies or pull the oil pan and replace the worn bearings, if the crank is not too damaged. I've read posts of some people driving for years with a motor that knocks. Maybe I'll get lucky.

I should mention I do have a slight oil leak from my front cover. I'll probably pull that to check the oil pump as well. This is an 03 so maybe the oil pump issue is rearing it's head and causing the front cover to leak. Perhaps it is just a bad gasket, wel'll see.
 
ptschram

ptschram

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Sep 27, 2004
21,955
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In the shop doing the Lord's work one broken Rover
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Troy:
You asked for info on how to check the oil pressure.

The oil pressure switch is on the right side of the engine, on the front cover. On a DII, it can be either a two pin, or a single pin connector. IIRC, the single pin switch has a 1/8" BSPP fitting. The two pin connector is 1/4" BSPP, again, IIRC. I was shocked to find the larger size when replacing one and was overjoyed that I had a crush washer to accommodate it.

Autometer makes an adapter for the 1/8" BSPP fitting to allow you to use an easily available oil pressure gauge which will almost certainly have 1/8 NPT fittings. Autometer refers to it as a "Metric" adapter. Yes, I've called them about it. I believe the part number is 2869, I don't know if they have one for the larger fitting.

WRT rod knock, typically an engine will make a gut-wrenching low knocking noise at idle, but the knock will lessen as engine speed increases.

Due to personal knowledge of a DII that ate camshafts in even faster fashion than most, I've come to recognize that some DII engines are prone to bad camshaft bearings/bores. Is the noise consistent with engine speed, or twice engine speed, or half engine speed?

I've also seen a truck ('96 DI) that had the most God awful lifter knock that ended up needing a headjob and a camshaft. In this case, the camshaft was worn down to the base circle and the lifter was riding on the un-machined cast portion of the camshaft.
 
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turbodave

Well-known member
Nov 26, 2008
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KY
The thread is actually M12 x 1.5.

1/4 BSP is a little over 13mm dia - and would have a 1.33 mm pitch if you measured it. The Form is also diffferent (55 degrees, rather than 60 metric) , such that if you stick metric thread gauges over a whit thread it's obvious something is amiss.
I don't know how you got your thread in there - but rest assured - the thread is M12 x 1.5 :)

Harbour freight have just got a pretty comprehensive oil pressure gauge set new in. There are like a dozen or so adaptors in there - and M12x1.5 is one of the industry standards today, so you can be assured it'll be in there.
 
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ptschram

ptschram

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Sep 27, 2004
21,955
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In the shop doing the Lord's work one broken Rover
www.ptschram.com
turbodave said:
The thread is actually M12 x 1.5.

1/4 BSP is a little over 13mm dia - and would have a 1.33 mm pitch if you measured it. I don't know how you got your thread in there - but rest assured - the thread is M12 x 1.5 :)
Click to expand...

Which thread?

I'm assuming the larger of the two. If so, thanx for the correction, I knew it was something bigger than the 1/8" BSPP, but wasn't certain of the exact dimension and was too lazy to go look for one to measure.
 
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turbodave

Well-known member
Nov 26, 2008
325
3
KY
Yes - my bad. It is the thread that is on the rectangular 'injector socket' style connector - as found on my 2003 D2 at least

I'm surprised 1/8 BSP was used as well (on earlier models I assume) - M10x1.0 is another common size for oil pressure threads, and given 1/8 BSP is 9.72mm OD and 0.909mm pitch, this could be why there is confusion, especially as there are only a few threads actually engaging.
I don't honestly know if the 'other' thread is metric - but given stuff on the disco v8's that was 'non buick' appears to be metric, I'd suspect the oil thread would be as well.

ps - I hope I'm not coming across as a smartass - I just have a perverse fascination with threads and thread forms!
 
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dragnet

Well-known member
Dec 23, 2008
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ptschram,

Seesm the knock is consistent with engine speed. I don't hear it at idle or when cruising. Only when accelerating or running uphill. I've checked exhaust for leaks, Seafoamed for carbon depsits and yesterday change the oil form the Castrol 5W40 to Mobile 1 15W50. Just wanted to see if any difference would occur. Knock is still there, but now I have another problem. The thicker oil causes a bad leak to occur at the front cover when the engine is running. With the engine off no leak. Running it pukes out oil at a pretty good rate. When I bought the truck it wsa doing the same thing for a couple of days. I switched to the thinner 5W40 oil and there was no longer oil spots on my driveway. Now back with 15W50 and it's leaving puddles.

I've also crawled under the truck with a long handled screwdriver and done the steth thing. Cats are fine, no noise from oil pan. Seems to be a little higher up in the block.

Not sure what to do at this point. Do I just replace the engine? Drive it until it dies? Pull the pan and see if it is fixable? Don't want to spend a ton of cash flogging a dead horse as they say.

I'm considering buying a 5.0 or 5.2 crate motor. Just not sure how it would run with the stock ECU.
 
singingcamel

singingcamel

Well-known member
Nov 17, 2006
2,752
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city of maples Iowa
www.singingcamel.com
Pull that darn engine and give it to me.
I have always had a slight knock with all my 4.0 's .
I run three disco 11 in the family and they all have a audible knock at time.
keep up the good maintence ..
I would'nt touch it until something happens.
Make sure your pick up tube isn"t all gummed up
 
ptschram

ptschram

Well-known member
Sep 27, 2004
21,955
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In the shop doing the Lord's work one broken Rover
www.ptschram.com
First off I confirmed the thread of the smaller oil pressure switch is indeed 1/8 BSPP.

From what you've just described, it sounds more like psark knock than bearing knock, uphill and under acceleration.

Replace your spark plugs and fill up with higher octane gasoline and see if it still does it. The fact it doesn't do it at idle pretty much rules out bearing knock as that is a noise that only occurs at idle, right up until the point that the crankshaft breaks, then it doesn't make any noise at all. With it only doing it under load leads me to believe it could be spark knock.

PT
 
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dragnet

Well-known member
Dec 23, 2008
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Would spark knock occur right from a cold start? From what I've read spark knock occurs when carbon deposits heat up in the combustion chamber cause bad detonation. Can this happen when the motor is completely cold?

I've actually been using the best fuel available here. It's a 94 octane. I just switched back to a 92 incase the octane rating was actually too high. Hasn't made a difference yet.
 
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dragnet

Well-known member
Dec 23, 2008
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Thanks,

I'll change the plugs and order some new leads. Still going to drop the pan just to see what it looks like in there. I've got a bit of a leak from the front cover so I'll address this at the same time and take a good look at the oil pump. Even if I don't find anything I'll be able to sleep better at night!
 
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