engine ticking/knocking

Topic: engine ticking/knocking (Read 897 times) previous topic - next topic

engine ticking/knocking

July 28, 2005, 04:44:20 PM

Ok I've got an interesting one for you guys. My friend has a 1989 Crown vic with a 5.0 SO roller engine with 125,000 mi. (same as a Bird or Cougar) that makes a ticking/knocking sound at idol no matter if the engine is hot or cold. At first I thought it was the common cold piston slap but after the car warmed up the noise continued. He has a tach on it and we noticed that it only makes this sound between 800 and 900 rpms. If the throttle is pushed just a little bit to make the car run at about 1000-1100 rpms the noise vanishes. Other than that noise the car runs fine and dosen't sputter or stall. I don't believe that it is a rod knock (noise should get louder/worse as engine speed increases) so I suspect that it is a valve or lifter sticking. If you guys have any suggestions before we go riping apart his 5.0 let me know. Thanks.

Re: engine ticking/knocking

Reply #1 – July 28, 2005, 05:23:05 PM

I had a similar problem with my motor. It started as a tick just as your friends, under 1000 rpm. It has now developed into a full on rod knock that runs from about 800 to 1700 rpm. Driving at speed though, I do not hear it and the car runs perfectly when it's not in one of it's moods. I haven't bothered taking it apart mostly due to my limited free time and lack of a garage. So yeah, she's gonna blow. Time to hit the dragstrip!

Re: engine ticking/knocking

Reply #2 – July 28, 2005, 06:01:12 PM

Had similar noise on my last 5.0,light tick at idle.
Turned out the timing chain was so worn it was contacting the cover and causing the noise.
It had 286km on it but the noise started at aroung 190kms or so.

Re: engine ticking/knocking

Reply #3 – July 28, 2005, 09:56:30 PM

Been extra hot where you guys are lately? Could be some things mentioned above.
Test the car's oil pressure. Take note of the pressure at startup. let it run at idle until the pressure stops dropping off. This is your warm idl pressure. Take not of that as well and when your done with that run the car at 2000 RPM while still warm and take note of that pressure as well. What weight oil is he runnin anyway and when was the last time it was changed?

Re: engine ticking/knocking

Reply #4 – July 28, 2005, 10:57:40 PM

The oil in his car was changed about a month ago and 10w30 motorcraft synthetic blend was put in along with a motorcraft fl-1a filter. We were just messing around with it tonight trying to figure out the problem and we did notice something. When the motor is knocking (800-900 rpms) it shakes a more than normal. If we hold the throttle open a little to bring it up to 1000-1100 rpms it's very smooth. I'm begining to expect that it is a loose rod because of the vibration. I'm thinking that it's time for an overhaul

which I'm not looking forward to. The car has been doing this for about 3 months or so but it has gotten steadaly worse. I whish that he would have realized that it wasn't piston slap sooner cause I think that if it is a rod that he's going to need a whole bunch of new parts in his block (ie. crank and rods). Well I'll tell him to check the pressure before we go takin his engine apart.

Hmm drag race the Vic to blow a rod out..........sounds fun cause it ain't my car

Re: engine ticking/knocking

Reply #5 – July 29, 2005, 01:38:12 AM

I had an 88 Grand Marquis that did that all the time.. especially under a load going up hills, etc. Of course, mine had 200k+ on it.

Re: engine ticking/knocking

Reply #6 – July 29, 2005, 11:11:43 AM

Well we figured out the problem. He has a busted cat! We unbolted the exhaust just for the heck of it and guess what the noise disappeared. We took y pipe off and shook it and sure enough it rattled. The thing that sucks though is that the cat is about a year old. Those Crown Vics are sure strong cause they can just blow out cats a random

. Well at least we now know that his engine won't throw a rod out while it's running. Thanks for the help guys.