loud rattling noise upon start up but then goes away on 1998 Dodge Stratus

I have 1998 dodge stratus with a 2.5 engine that makes a loud rattling noise upon start up but then goes away immediately. It runs good for abot 20-30 minutes and then the engine starts to get hot (but not fully over heating) and then a valve train ratting type noise starts. I was told by a couple people that it was the oil pump, but after removing the oil pump and examining it did not appear to be worn or defective. Is it the oil pump or is it something else?

by in Fairdale, KY on September 07, 2013
1 answer 6 comments
ANSWER by on September 07, 2013
You pulled the oil pump OFF of the engine??
COMMENT by on September 08, 2013
Yes. I also inspected the main and rod bearing and did not see any apparent damage. I did however just notice quite a bit of sludge in the bottom of the oil pan which could possibley clogged up the sifter screen but not sure if that could be the problem?
COMMENT by on September 08, 2013
Cant tell by looking if pump is needed!! Replace pump and pickup tube. Clean sludge from pan. Pump is in the front of the engine driven by the cranksfaft, right? It is possible the relief valve is weak, but it comes with the NEW pump.
COMMENT by on September 08, 2013
How can you tell if is weak? I attempted to disassemble the old pump, but could not get the phillip head screws to come loose, but I did get the spring and cap loose and removed and did not see any apparent damage either. I removed the pick up tube and observed the rotors from the pickup tube inlet hole and did not see any apparent damage to the rotors either, but I may be wrong since I can not get it completely disassembled. Could there be something else internally other than the rotors that I am not seeing? Thanks for your help, by the way
COMMENT by on September 08, 2013
Oh yes, there are many places you can lose oil pressure in an engine! The only way to see this is a complete tear down. Suggest putting it back together with NEW parts and hook up a manual pressure test gauge! Ebay got some good deals on the pump!! Dont opt for the cheapest though! Put some 10w30 sae oil back in it. Also some Lucas oil stabilizer will help a BUNCH!! NAPA GOLD or WIX filters are hard to beat. Good luck with it, let us know how you make out.
COMMENT by on September 08, 2013
Where else can I lose pressure? Will do, and thanks again!
COMMENT by on September 08, 2013
Cool, now don't put that old pump & pickup tube back on, go ahead and replace both! And use the oil(s) and filters i suggested.