engine and drivetrain Knock Knock... Who's There? Knock Knock.

[Rocan]

Started car today after adjusting brakes. Heard the dreaded noise of doom... knock knock knock... 

 

Check cylinder head, all was well. Drained oil looking for metal, found nothing, but oil was WAY too dirty. Also, there was only 2 liters of it. No good. 

 

But my oil pressure light didn't come on. And my dipstick was okay... a bit on the low side, but OKAY. Refilled with good oil to four liters. Oil pressure light is now stuck on. no good. let it build pressure, knock went away, all is well. Hallelujah. Was not looking forward to having to pull the motor twice in one year. 

 

Here's what I think happened...

 

When I resealed my motor a few months back I changed the oil, but had been running detergent oil to clean things up a bit. My oil pressure light would flicker at idle but go away just off idle, so I assumed "worn oil pressure sender" since my oil level was okay. Somehow my pressure sender got stuck with the light off so that the light wouldn't go on warning me to pull over and add oil, ya knucklehead. 

 

Oil level got low, pressure got low, knock came because of it. the level on my dipstick is slightly off... by about a half liter. Not enough to cause issues, but I need to keep in mind that the bottom line is about 2 liters left, not 2.5-3 liters. so top line every time. 

 

 

Check your oil people, and if your oil light flickers, change the sender. Save yourself the heartache that I went through today. 

 

 

 

 

Also, check your brakes. My rears were really worn and the adjusters weren't doing any adjusting. 

 

 

Finally, a question... One of my handbrake cables is nearly bottomed out in the adjuster because of slack in the cable. the other is about midway... seems to actuate fine. perhaps someone swapped in a wrong cable at some point that was too long? or am I missing something. 

[OriginalOwner]

 brake cables .... mine are original and have always had different lengths.  IMHO, no biggie .... the parking brakes have always functioned as expected.

 

Cheers,

 

Carl

[Guest_anonymous]

Do you know the actual pressure the oil pump is putting out?

Edited June 8, 2013 by daron

[ray_]

Also you can gain more ebrake adjustment by adding a spacer at the handle end of the cable.

 

GL,

[Rocan]

Do you know the actual pressure the oil pump is putting out?

 

No idea... I have a gauge or two in my basement I could use... just have to figure out where to hook them up. 

 

 

Thanks for the advice on the ebrake... I figured it was fine, just a bit odd how much longer one was than the other. 

[Cyclone101]

Yup, my hand brake cables are different lengths as well. Just make sure they have even tension, otherwise it makes open parking lots less fun...

 

I would think you need to check the pressure at the pressure sender port, you might get different readings at different locations.

 

Glad it was't anything major!

 

Regards

Jacques

[Rocan]

The knock is back, this time the oil is topped off. It's there at first start but as soon as oil pressure builds it goes away. Can chain tensioner or rod knock? I figure rod knock would always be there, and get worse with warmer oil, this seems to only appear with low pressure.

[Emyers]

The knock is back, this time the oil is topped off. It's there at first start but as soon as oil pressure builds it goes away. Can chain tensioner or rod knock? I figure rod knock would always be there, and get worse with warmer oil, this seems to only appear with low pressure.

Next time it knocks, remove the ignition lead to each sparkplug one at a time with the motor running.  If the knock goes away when you remove a lead for a given piston, you have isolated the offending rod.

Earl

74 02Lux

02 M Roadster

72 Volvo 1800ES

[ray_]

I think it's broke.

 

;-)

[Rocan]

Next time it knocks, remove the ignition lead to each sparkplug one at a time with the motor running.  If the knock goes away when you remove a lead for a given piston, you have isolated the offending rod.

Earl

74 02Lux

02 M Roadster

72 Volvo 1800ES

the problem is that the knock is only there for the first few seconds of running; nowhere near enough time to determine the problem.

 

I guess stethoscope down each spark plug while cranking the motor by hand is the only way?

[ray_]

Pull one wire. Start. Repeat with other wires.

 

;-)

[Rocan]

I'll try, but it only happens for a short period of time, not nearly enough to start the car and run to the engine bay to unplug a lead. 

 

Who can tell me what I need to hook up an oil pressure gauge for diagnostic purposes (to see if im getting a fluctuating reading or low reading)?

 

I'll drain the oil and replace the filter this weekend and look for bad things, hopefully worst case scenario I can just replace the main bearings with the oil pan off as a temporary bandaid until I can find a garage to swap the new bottom end on. 

[Rocan]

I just ordered a new fun tool....

 

http://www.amazon.com/gp/product/B000R5G0DO/ref=ox_ya_os_product

 

Should be useful for years to come, and has adapters for most any thread.

[ray_]

I'll try, but it only happens for a short period of time, not nearly enough to start the car and run to the engine bay to unplug a lead. 

 

Who can tell me what I need to hook up an oil pressure gauge for diagnostic purposes (to see if im getting a fluctuating reading or low reading)?

 

I'll drain the oil and replace the filter this weekend and look for bad things, hopefully worst case scenario I can just replace the main bearings with the oil pan off as a temporary bandaid until I can find a garage to swap the new bottom end on. 

 

 

That's why you unplug the lead(s) BEFORE starting. Sort of like what I wrote.

 

:-)

[Hans]

For the record (in case it wasn't included above) the oil pressure warning light is for low pressure, not low oil level. An engine can happily put out 60psi pressure until it runs out of oil to suck from the pan. What may happen when the level gets really low is that the light may come on as the oil sloshes around and leaves the pick-up uncovered for a few seconds. If your oil light flickers at idle (car stationary), it may be trying to tell you that the pressure is below -7psi? I think. Which could be that your idle is too low, your oil choice is too thin, your bearing clearances are too big, your oil pump is tired OR yes, perhaps your sender/wiring is flakey. If memory serves, the light goes on if the wire to the sender is grounded (ignition on). In which case, having the light always on could be an electrical issue. But it could also be that you have no oil pressure.

I'd be checking actual oil pressure with a gauge (try Harbor Freight), and then main and rod bearings in situ with Plasti-gauge before getting carried away.