rattling dodge intrepid

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rattling dodge intrepid

Postby mcautoak » Tue Mar 05, 2013 2:21 am

This car was sent to me from another shop because they were too busy to get to it, and the lady needed it repaired ASAP.
Symptoms were engine oil warning lamp would flicker when engine was first started cold. After warming up the oil lamp stayed on and the engine had a loud rattling noise. The first shop replaced the engine oil filter, but not the oil as it looked fairly clean. This made no difference. They were kind enough to put the old filter in a bag and sent it to me with the car.
When I cut the filter open I found no sign of metal or any engine wear. I was able to duplicate the symptoms. The engine sounded normal when cold, but as it warmed up it developed a rattle/ knock and the oil light stayed on.The rattle almost sounded like lifters, and was coming from the front of the engine. A visual inspection showed the engine oil lamp sender was leaking. I verifyed oil pressure with my WPS500 & pico scope. I like using the WPS for engine oil pressure as it shows exactly what the oil pressure is doing. I have found a couple restricted oil pickups this way.
Thinking the rattle could be a timing chain I also put cam and crank sensors up. As you can see, when cold there is 890 micro seconds between the cam & crank pulses and oil pressure is very good at 75 psi. After the engine warmed up there is now 1.71 milli seconds between the same two pulses and oil pressure is still good at 29 psi. This made me believe the timing chain tensioner had failed. When I replaced the tensioner and oil pressure sender all was back to normal. I forgot to save an after repair screen, but looked the same cold and hot , except oil pressure dropped to 30 psi.
We had told the customer before we started that she might be looking at replacing the engine. She was very very happy to find out what actually fixed it.

cold oil press.jpg

cold oil press.psdata
cam, crank, and oil press cold
(819.04 KiB) Downloaded 478 times


hot oil press.jpg

hot oil press.psdata
cam, crank and oil press hot
(836.3 KiB) Downloaded 429 times
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Re: rattling dodge intrepid

Postby Lee » Tue Mar 05, 2013 6:27 am

Great find with the WPS500X

I have used the WPS loads on oil pressure systems, its great as it shows all the pulses from the pump so effectively you see every pump cycle, great for finding a pump thats not pumping capacity and its great for looking at pressure oppose to a fluttering analogue gauge.

Well done.

Kind Regards

Lee :D
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Re: rattling dodge intrepid

Postby AuthorMike » Tue Mar 05, 2013 2:34 pm

Great work, thanks for sharing. I hope you don't mind but I added some screenshots to your post.

Mike
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Re: rattling dodge intrepid

Postby mcautoak » Tue Mar 05, 2013 10:02 pm

Thanks, I don't mind at all. That was my first time posting to this board. I thought I had atached the screen shots, but I must have done something wrong.
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Re: rattling dodge intrepid

Postby AuthorMike » Wed Mar 06, 2013 10:00 am

Hi,

The data files were attached. I merely created JPGs of the two files and added them to the post :)


Thanks again for the contribution,

Mike
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Re: rattling dodge intrepid

Postby arjen » Wed Mar 06, 2013 7:48 pm

Nice case study!

The Wps500 is high on my list..

I have a question about the timing.
Did you took the capture of the timing at cold and warm engine at the same rpm?
Otherwise the timing is not the only thing cousing changing in the time between cam and crank pulse.
For example:
If the time between signals is 1 ms. at 1400 rpm (cold engine), than it would be 2 ms. at 700 rpm (warm engine).
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Re: rattling dodge intrepid

Postby mcautoak » Fri Mar 08, 2013 8:22 pm

Great question. Yes they were both at about 750 rpm. I should have mentioned that in the original post. From now on when I post something I will make sure all the screen shots are zoomed in the same to make comparison easier.
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