please help with bad noise

[kaos2tru_240sx]

Ok i have a 1990 240sx with the ka24e SOHC engine getting a noise from under the valve cover, the noise goes away when the engine warms up though, if i watch the temp gauge as soon as it gets to norm operating temp the noise is completely gone, i've removed the valve cover looked at the chain guides they look fine the chain has no play i'm confused i'm a mechanic for a ford dealership and all my co-workers are confused if anyone can give me some clues i don't want to have to rip the front cover off unless i have to does anyone know of what this might be i even suspected the water pump for a short period

[deviousKA]

sounds like your timing chain, could be your lifters, but the symtoms point to stretched chain and/or weak tensioner. You can tell the sound of a ka24e chain dragging against other components, it is a constant loud dragging type sound. Bad lifters will click and clack with pauses. A weak oil pump can also have lead to these problems and should be checked as well.

[kaos2tru_240sx]

the problem with that is that it's not a constant noise, when the t-stat opens the noise is gone until i let my car sit and cool off but if i start if up again after 20min or so no noise but as soon as it's cold there's the grinding noise

[Scott McLellan]

Maybe check the valve lash. I have a friend with a newer camaro and he was having noises right when he started a cold engine. The dealer said he needed to have his valves adjusted. He also just recently had his water pump replaced, but I don't know about yours. Just some ideas. Good Luck!-Scotty

[BomexS13]

I have the same "grinding" noise problem....i'll take out the valve cover tomorrow to see what going on underneath

[deviousKA]

You cant tell timing chain problems by removing the valve cover and looking most of the time. One thing you can check is how far the tensioner is pushing the chain out (indicating slack) if your looking down from front it will be on the left and have a small cylinder pushing out on the left chain guide. If it is pushing out a 1/2" or more you have chain slack. Chain is probably rubbing against chain oiler peg if its grinding and you see this. If you notice your guides are broken or damaged (mainly the right) chain is all over the place.

ka24e has hydraulic valve lash adjusters, if one or more is severly damaged, it will click clack. When the lifters are dry they will take up to 30minutes to clear up or bleed with the engine running, You should only have to do this if they have just been installed or if they have been sitting for long period of time without oil flow. If you suspect its the lifters everytime you start up, instead of the timing chain, to much oil is bleeding out of them and/or weak oil pump.

[Altiman94]

how would you stop the oil from bleeding out and how do you cheak fora weak oil pump?

[deviousKA]

them bleeding out isnt really as much of a problem if the car is driven daily. It can sometimes be caused by worn rocker shafts/rocker bearings. To fix this all you can do is buy new rocker shafts, hone the scarred lifters or buy new ones.

You can check your oil pressure while running, both at idle and higher rpm with cold and warm starts. You can put a t-fitting at oil sender for mechanical autometer type gauge to check.

If you have a few different datsun/nissan sohc type oil pumps you can check them by filling with oil, covering large return with thumb, and hand-driving them with the best shaft you have. You should be able to feel any bypass problems and you can compare to find the one with tightest feel.