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motor knocking sound at start up?


Heroez

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Stock 83 turbo car, 199k on odometer, hydraulic head, recent oil change. Last couple days when I start the car in the morning it makes a loud slapping/knocking sound for a second then stops. It seems to be coming from and in time with the motor. After that it goes away. I dont hear it on the next start that day or during driving. Any insight on what it may be?

Edited by Heroez
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You could have the incorrect oil filter installed. You need to make sure it's an anti-drainback filter, and if it is, then make sure the anti-drainback valve isn't broken....not sure how to check that except put on a new filter and see if it goes away.

 

What's happening is that the oil is draining back down out of the cylinder head, and on initial startup the oil galley up to the head has to refill, and one or some of the lifters have bled down. Once the oil pressure comes up, the noise goes away.

 

Also, might be time to check your oil pump, and check your lifters individually to see if any of them are sticking. But what you've described sounds like lifter slap, acts like lifter slap, and could probably be cured, by treating it as lifter slap.

 

It's a duck.

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Same thing happened to me last year. 2xx,xxx on the clock. Had this happen on a couple of cars, both without hydraulic lifters, and both motors went down due to rod knock. Worst case scenario (and my guess), worn rod bearings.

 

Come to think of it the last time I pulled a motor that failed the check ball in the block was gone.

Edited by B. Whisky
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Oh, Ok. I will start with an oil change with a quality filter and see if it helps. I got tires recently maybe a month ago, and had them change the oil while they had it. They may have used a crappy oil filter. I will post any updates. It must be my lucky week because my car didn't want to start after work. Turn key, wait for fuel prime, Click. Hmmm. Click. It did this like 5 times. I wiggled the wires going to starter. Click. Then next try it started up. I don't have a lot of confidence in this car right now. Have to drive it to work tomorrow. I guess I will keep my fingers crossed and hope for the best.

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I always need some work done. Im weak at mechanical, but trying. Want to do a zx head gasket? Well, it seems like a gasket with coolant going out the exhaust. I suppose it could be worse, damaged head.

Edited by Heroez
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  • 1 month later...

Did the oil change. Wix filter, Mobile 1 15w 50. It didnt do it for a couple days. This morning the rapid tapping/slapping sound was back. Just at initial start up for a second or two. Tried to search "lifter slap" but didnt get much. Is there damage markers I should look for under the valve cover? It seems bad for the car when it does it. If the oil pump needs replacing, can you lift/support the engine, then remove the front cross member to let the oil pan drop?

Edited by Heroez
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That is 99% a bad lifter/s try running a quart of ATF in the oil, sludge etc can cause this and atf Has a lot of detergents in it. If that doesnt work you need to find some lifters or a solid p90 head. I have cured 2 cars start up knocks with atf. Usually a day or two and its fixed

Edited by calvin280zxt
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That is 99% a bad lifter/s try running a quart of ATF in the oil, sludge etc can cause this and atf Has a lot of detergents in it. If that doesnt work you need to find some lifters or a solid p90 head. I have cured 2 cars start up knocks with atf. Usually a day or two and its fixed
Hey, thanks for the reply. Your experience/wisdom is greatly appreciated! Im surprised I had not heard of this problem before. I will follow your advice, and report results. So basicly Im going to drain a quart of the new oil and add the ATF. You mentioned a couple days. How long should ATF be used? A week, or the next oil change?
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You don't need to drop the pan to change the oil pump on any L-series engine. P90 Hydraulic lifters are prone to lifter slap when cold-started if they are worn or dirty...and most are just dirty.

 

You can start the car, run it a few minutes until the noise stops, then turn it off and pull the valve cover. See if any of the HLA's are slack. They should hold oil in them for at least an hour, if they're dropping off right away then they are likely worn or dirty. What happens is that the lifter doesn't hold the rocker arm against the cam, and the cam lobe slaps against the rocker arm, which makes the noise you're hearing.

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I would run it for a week or two then change it and run a little bit in with each oil change 1/4 jug or so, 15-50 might be a liitle thick at startup contributing to the problem, i havent run any thicker oils though so im no expert

Will do. Thanks for clarification. The cars history folder had that oil type written on it, and there was a spare quart in the hatch bin. It matched up with a recommendation, so I Just use mobile 1 15w 50. Its something I should look into more on oil choice. At 60 dollars in oil and filter, maybe an alternative would be helpful. Oddly, most stores dont carry that here.
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You don't need to drop the pan to change the oil pump on any L-series engine. P90 Hydraulic lifters are prone to lifter slap when cold-started if they are worn or dirty...and most are just dirty.

Im sorry. I was confused. I have been thinking of the front cover lately. I am still a student on the motor, but learning. Its nice to know that most get dirty. Seems like something that is fixable without a big fuss. Would you happen to know any tips on getting them clean? If they are dirty. When I changed the oil it was so dark black. Took a cheapy fram filter off it that the tire place used. Love the tires though.

You can start the car, run it a few minutes until the noise stops, then turn it off and pull the valve cover. See if any of the HLA's are slack. They should hold oil in them for at least an hour, if they're dropping off right away then they are likely worn or dirty. What happens is that the lifter doesn't hold the rocker arm against the cam, and the cam lobe slaps against the rocker arm, which makes the noise you're hearing.

Ah, now it makes sense. I knew the wiper arm was being beat up by the cam... you made it click as to why. Thanks for the advice on what to look for. I feel like I have to do an inspection of some sort. You can relate, Im sure. Its nice to have you guys here. Edited by Heroez
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The oil pump just drops off with four bolts. The sway bar is in the way. No need to unbolt anything but the passenger sway bar mount, and the four oil pump bolts. You will get oil all over you.

 

The cleaning of hydraulic lifter assemblies is documented on this site pretty well. It's not difficult, but it does require some faith that when you put it together it'll work...and it won't always work.

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