Mid RPM Chirp/Can't find answer
08-25-2016, 05:40 PM
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Mid RPM Chirp/Can't find answer
Hey all. Long time reader, first time poster. So, the vitals:
-1998 F150 XLT 4x4
-250,000+ miles (orginal)
-4.6L
-All stock, no after market
-Chirp when running
I looked all over the interwebz but can't find an answer that specifically addresses my problem. There seems to be a lot of possibilities though. I just figure it's smarter to ask before I head off to the parts house and buy another thing that doesn't fix it. So, the problem:
1) Alternator took a crap. Replaced; everything worked as advertised.
2) Drove and about 2 wks later, a chirp developed once engine got to normal running temp. Don't worry...lol...keep reading.
3) Replaced idler pully. Still chirps.
4) Got rid of A/C compressor. Installed new non-A/C (bypass) belt tensioner and belt. Still chirps.
5) Replaced cooling fan clutch. Still chirps.
Conditions of the chirp:
1) At running temp.
2) In park or drive(ing). It's running engine linked.
3) When cool(ish), there's always a *puft* sound until it gets to temp, then a full on chirp at...
4) Chirp starts at about 1.5K/RPM and speeds/slows with RPM change. Loudness and tone doesn't change however. Just speeds up as the engine spins faster.
What I've done to trouble shoot:
1) Checked plugs. Yep, I've had plug problems in the past, but none since last shop visit.
2) Poor man's stethoscope (broom stick) checked engine all over. No 'sound' other then the engine telling me it's tired. I don't hear the chirp thru the stick. I however didn't crawl underneath.
3) All points to the new alternator, but the chirp seems to come from underneath and passenger side wheel well.
4) If you goose the gas and jump it fast to 2 to 2.5K/RPM, there will be a sharper, almost louder, first chirp, and then it settles in to the normal brain numbing tweety bird holding at that RPM...or any RPM below 1.5K.
5) I can almost pin point the sound to the passenger side, but it's hard be certain. The chirp seems very centric to the block/engine.
6) I thought at first of an exhaust leak because of the *puft* sound when the engine temp is cooler, but then I read about the cam sensor and the chirp versus cam sensor scenario from other posters seemed pretty realistic.
7) The chirp gets pretty persistent and consistent the hotter it is outside.
I do most all of my own repairs but I don't have a fully stocked garage. I've changed everything I could think of up front and yet the noise persists. Normally I would root-cause-analysis to the alternator but the proximity of the chirp just isn't there. All I can think of is if I should do the cam sensor AND both exhaust manifolds. I'm not fond of that idea, and I'm no expert, and don't want to waste the money if it's something simple that I'm missing.
So, first off, thanks for reading thru all that. Any questions, clack away. Thanks in advance for any help.
-1998 F150 XLT 4x4
-250,000+ miles (orginal)
-4.6L
-All stock, no after market
-Chirp when running
I looked all over the interwebz but can't find an answer that specifically addresses my problem. There seems to be a lot of possibilities though. I just figure it's smarter to ask before I head off to the parts house and buy another thing that doesn't fix it. So, the problem:
1) Alternator took a crap. Replaced; everything worked as advertised.
2) Drove and about 2 wks later, a chirp developed once engine got to normal running temp. Don't worry...lol...keep reading.
3) Replaced idler pully. Still chirps.
4) Got rid of A/C compressor. Installed new non-A/C (bypass) belt tensioner and belt. Still chirps.
5) Replaced cooling fan clutch. Still chirps.
Conditions of the chirp:
1) At running temp.
2) In park or drive(ing). It's running engine linked.
3) When cool(ish), there's always a *puft* sound until it gets to temp, then a full on chirp at...
4) Chirp starts at about 1.5K/RPM and speeds/slows with RPM change. Loudness and tone doesn't change however. Just speeds up as the engine spins faster.
What I've done to trouble shoot:
1) Checked plugs. Yep, I've had plug problems in the past, but none since last shop visit.
2) Poor man's stethoscope (broom stick) checked engine all over. No 'sound' other then the engine telling me it's tired. I don't hear the chirp thru the stick. I however didn't crawl underneath.
3) All points to the new alternator, but the chirp seems to come from underneath and passenger side wheel well.
4) If you goose the gas and jump it fast to 2 to 2.5K/RPM, there will be a sharper, almost louder, first chirp, and then it settles in to the normal brain numbing tweety bird holding at that RPM...or any RPM below 1.5K.
5) I can almost pin point the sound to the passenger side, but it's hard be certain. The chirp seems very centric to the block/engine.
6) I thought at first of an exhaust leak because of the *puft* sound when the engine temp is cooler, but then I read about the cam sensor and the chirp versus cam sensor scenario from other posters seemed pretty realistic.
7) The chirp gets pretty persistent and consistent the hotter it is outside.
I do most all of my own repairs but I don't have a fully stocked garage. I've changed everything I could think of up front and yet the noise persists. Normally I would root-cause-analysis to the alternator but the proximity of the chirp just isn't there. All I can think of is if I should do the cam sensor AND both exhaust manifolds. I'm not fond of that idea, and I'm no expert, and don't want to waste the money if it's something simple that I'm missing.
So, first off, thanks for reading thru all that. Any questions, clack away. Thanks in advance for any help.
