Best of Deals Car Reviews Repair Shops Cars A-Z Radio Show

HELP! Road trip with rod knock!

My poor baby just developed a rod knock. The noise usually is faint and only when accelerating slightly. I had one bout of very loud vibrating “humming” and clanking. I need to drive to NH from WY (2500 miles). Is there a chance this noise could be something else? How can I prolong the life of the car to get home? Any tips would be appreciated. I hear cars can last anywhere from 1 to 100,000 more miles with this issue. I am hoping for the latter. She’s a 95 Saturn SL1 and I love her, but I understand her time has come.

Change your engine oil…and if it holds 4qts…then substitue 2 qts of GEAR OIL in place of motor oil. I would use 10W-40 2qts…and 2qts of 85W Gear oil…the added viscosity and thickeners in the gear oil will most likely silence that knock. Just remember to be sure to let your engine warm up before driving…the added viscosity puts additional strain on your oil pump drive and if you take off while cold you could hurt your oil pump…but this is rare and if you follow instructions of warming up you will be fine.

This is an OLD School “Trick” that mechanics use. Its safe give it a shot…might silence that knock for good or at least reduce it a great deal.

If you dont like this idea you can go to using all 20W-50W motor oil…I always use the gear oil trick and it works quite well…it fills in that additional space that has opened up in the bearings which creates that knock…the thicker oil will cushion this extra space …been working on cars over 20Years…and have done this trick many x…it works when the knock isnt too bad

I don’t quite agree with you. I don’t think it is rod knock, that would be loud and constant. If it were a collapsed lifter, the heavy oil would aggravate it. It sounds most like a loose and worn out timing chain. I don’t think heavy oil will make it much quieter or help it last any longer.

An oil change would be a good idea though. Since its close to summer, straight 30 HD might be warranted but a diesel rated 15w40 would be my choice for this case. It has the best lubricity. Diesel oil has a couple of components no longer allowed in gas engines due to alleged damage to catalytic converters.

Kieth does make a good point. I just took you on your word about the knock. Hmmm what else could it be? It would definitely always be there and not go away…so again Keith got it right. If it sounds like a sort of “loose” sound or rather like chattering…that would be your Timing chain being stretched beyond the adjust limit of the Hydraulic Chain tensioner…Did it sound chattery? If so I would second the chain idea…not that serious…or I mean that can be repaired and nowhere near as bad as a Rod Knock at all.

Thanks guys for your input! At first I thought it sounded like a “vibrating hum” but there isn’t really an accurate way to describe it. Then I described it as a “vibrating grind”… It’s not a tik, tik, tik kind of noise. It is not constant, and it comes and goes periodically. I took it one mechanic yesterday and he said it was a rod knock after he heard the sound. I am not sure if he took a look at the bearings or anything. I am planning on getting another opinion and bringing your ideas to the table.

A rod will “hammer”, steady rhythmic knocking sound…Not a loose, splashy clattering sound. A rod will become more noticeable when you “goose” the engine in neutral and stop for a moment when you back off…Sometimes you can remove the spark-plug wires one at a time and when you hit the bad cylinder, the noise stops…

If you can get the oil pan off without taking half the car apart, a good old-time mechanic can slide in a set of bearings in about 3 hours…A four-banger, less than that…