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

87 Chevy Rod Knock?

My 87 S10 (2.8L) recently began knocking. It only knocks when the motor is warm and increases as RPMs increase. I had a friend who is a mechanic look at it and he said it was rod knock.

My situation: I have to get my truck back home from college. It’s about 100 miles and over a mountain pass. What are my chances of blowin’ a rod? Would it be better to just run the truck on 5 cylinders?

You are asking if you should continue to operate an engine that has been diagnoised to have a internal engine concern? This concern is a rod bearing that is so worn that there is an audible indication of this wear. I certainly cannot recommend continued operation of this engine. I ask you (the OP) why would you believe that continued operation of the engine would not be a bad thing (in regards to what can be repaired as opposed to replaced when it comes time to remedy the rod knock)?

Perhaps you say “all I need is to get 100 more miles out of this engine and then I scap the engine and start totaly over”. If the case is that all that is needed from this engine is 100 more miles of operation and your question is “should this last 100 miles be done with the problem cylinder deactivated” I would say that there is some logic in the idea that this engine stands a better chance of making the journey with the plug wire pulled, can’t say for certain.

Are you ready to deal with a blown engine? 100 miles isn’t that big a deal, can’t mom, dad, or friend come and get you at school?

If you need to replace the motor that can be done anywhere, you don’t have to be “home”. If you just want to drive the truck into the ground then drive it home. It will likely make it the 100 miles.

Take it easy on the drive. You can try pulling a plug wire and see if the “knock” is less pronounced. I don’t really think it will make much of a difference, but it might. Just pulling the plug wire and leaving the plug in the cylinder means you are pumping a lot of raw gas in the catalytic converter if the truck has one. If you have a cat it could overheat and that’s not good at all.

If you have multipoint FI you can pull the connector on the fuel injector and pull out the spark plug. I don’t think pumping air without any compression would hurt the rod, but you have to identify which cylinder is the bad one.

So, I’d just leave it alone and run it easy, slow and easy.

My bet would be that the engine wouldn’t survive 100 miles of mountainous highway. If you are determined to try I would suggest that just before leaving you warm the engine up to normal temperature and add a bottle of Lucas or STP or similar oil thickeners and pay close attention to the knocking and how it can be reduced paying close attention to the RPMs and the load on the engine. If you throw a rod the engine will likely become scrap. It won’t be an acceptable core for a rebuild. FWIW, I did limp a Ford truck with a 302 engine over 60 miles with a rod knocking after pouring in 2 cans of STP. But I was lucky.

You SEEM adventurous and since the engine is a gonner…TRY THIS…lol… Drain your oil… refill the crankcase with 2-3QTS of GEAR OIL…the rest with 10-30 or 10-40…I guess the remaining 2 qts… Then start her up and take a listen. If you had a mild rod knock…I know you dont hear it as loud anymore or at all…with that oil in there. See what you get, you have nothing to lose by trying it out BEFORE you hit the road…right?

But seriously we all know how bad a rod knock is…and if you dont…look it up, it aint pretty. You would be surprised sometimes how far people can push an engine with a rod knock…If seen people drive for a few years…which is totally nuts and they know they could have been stranded at any second…but…Hey the Blues Brothers drove 1/4 of the movie with a Rod knock…lol.

Try the oil trick you may be shocked…and I only say this because the engine is going to be replaced or rebuilt. You def dont want to throw a rod or seize your engine in the middle of a 100 mile trip…Try the gear oil and see how the knock is. Now if it is a BAD knock forget it but in this case it doesnt seem like it is…You could make it…gently. I do lots of test driving first but…LOL…I’d try it. Try at your own risk of course, but you may be surprised if you hear that the knock is gone with some gear oil…

I’m sure I will catch flak for this, but…thats OK

Funny I never read other peoples answers…and I just did…look at what RodKnox said…same idea but more extreme in my case…

The best approach would be to do a one-way rental from UHaul and tow the S10. Right now you need a rebuild on the bottom end. If that seizes and breaks while driving you lose the engine entirely…and the tow home will cost you much more than the UHaul rental would have.

If it knocks only when warm and when oil is consequently thinner, that increases your chance of making it with thickened oil. Try thickened oil to warmup and if no rod knock, proceed with caution meaning drive slowly.

Consider too if you arrive at home with your S10 if you will want to spend the money to repair a 14 year old vehicle, especially if it is rusted. It might be best to scrap the vehicle where you are and then take the bus.

A “rod out” was common in the early days and largely became a thing of the past in the very early 1950s. A rod out now is almost unheard of and almost certainly can be attributed to very abusive driving plus lack of maintenance rather than a manufacturing defect.

It is not likely piston slap as that often goes away with engine warming with consequent piston expansion to better fit the cylinder.

Thanks for all the input. I am not planning on rebuilding the motor or dropping a new one in. Chance are I am going to just sell it for scrap. If I do decide to take it over the pass I’m going to put some Lucas (they recommend up to 60% for badly worn engines) or a heavy weight oil in it. I just need it to make it over the pass and make 4 or 5 trips (10 miles round trip) over the next couple months. It’s not knocking too bad yet so I hope as long as I take it slow it should be OK for a while.

If a thickening additive is more than about 25% restarting the engine cold can result in further damage to the engine. I saw an oil pump drive wound up like a cork screw from an engine with 20-50 oil and a quart of Lucas being started at about 15*F.

How bad of a knock are we talking about? Is it a light tap or a serious pounding where you can’t hear yourself think while driving? If it’s a light tap, the engine should make it. You may not even notice it at cruising speed if the engine still has decent oil pressure.

There have already been alot of good advice here on your engine concern,but i would like to reference the part about selling it for scrap. As a fan of this era of s-10 i would rather you sold it to someone for a few hundred bucks who will get it back on the road with say a nice 350 under the hood or newer model 4.3,just a thought. The 2.8l was a dog in these trucks,would rather have the 2.5l 4cyl. These trucks really do clean up nice. I personally have an 89 with the 4.3 and an 87 waiting on a V-8.

I would agree with trying a heavier oil but I would not get carried away with it for this reason.
You do not really know how much clearance exists on the bearing that is knocking. If it’s somewhat excessive and you use oil that is too heavy it’s always possible that the heavy oil, especially when cold, could cause one of the bearing shells to rotate and swap sides.

This means both shells would be on the same side and within a fraction of a second you will probably be walking. Maybe 20/50 but I would not use anything heavier including oil stiffeners such as STP, Motor Honey, etc.

If it’s not knocking cold then my opinion (a.k.a. wild guess) is that it will be ok to use with a heavier oil. On the upgrade I would try to baby it a bit and if that involves slowing down a little and people behind you getting mad then so be it.

It’s barely noticeable if the radio is on, even at a low volume.

I was thinking of draining the oil then adding 3 quarts of 10W-30/40 and 2 quarts of Lucas? It tends to leak a bit of oil so I was thinking of maybe just adding Lucas instead of the 5W-30 I’m using now, probably not more than a quart though…

I had it on craigslist for a while…I was only asking $500 for it but it seemed everyone was looking for a perfectly running truck for dirt cheap. That was even before the knock got bad and my friend diagnosed it. I will definitely try to sell it before I take it to the junkyard.

I’ll keep that in mind. It’s still pretty cold over here (20’s at night, and got down to the single digits last week). I was thinking of just adding 2 quarts max of Lucas to the 5W-30 I’m running in it now.

Well, don’t quote me on this, but I think you’ll have no problem. I drove a car that had a similar problem for months, until it got loud enough that I thought I was pushing my luck. A new set of bearings and it was running fine when I got rid of it. If it’s a light tap and the rest of the truck is in good shape, you might consider throwing a new set of rod bearings in it and seeing how long it will last. I would consider using 20W50 oil in it though.