3.0 Dodge Caravan engine rattle...

[Nitrohaulic]

Any Mopar techs here who might be familiar with problems particular to these engines? This is in a 1995 with 150,000. Started out faintly weeks ago and now sounds like a diesel. Using a rubber hose as a stethoscope it seems the loudest just under the thermostat housing. I put rods and mains in it a year ago and it's definitely not coming from below. Runs fine with no missing. It doesn't have that hollow "thoop" sound of a wrist pin.

 

[Jenn]

Any Mopar techs here who might be familiar with problems particular to these engines? This is in a 1995 with 150,000. Started out faintly weeks ago and now sounds like a diesel. Using a rubber hose as a stethoscope it seems the loudest just under the thermostat housing. I put rods and mains in it a year ago and it's definitely not coming from below. Runs fine with no missing. It doesn't have that hollow "thoop" sound of a wrist pin.

Is it at all engine speeds or a specific range?

Ideas:
The #1 rocker arm has a tendency to crack, not cylinder head cast specific as far as I know. Last time I saw that was in the 2500 RPM range.

Chrysler corp also had a TSB on a valve train noise, I'll have to check on the specifics but I think it was 97 model year but since Chrysler hasn't really swayed much from it's original 3.0, 3.3 and 3.8 (?) designs, it's possible it's inclusive.

 

[Nitrohaulic]

Thanks.

When we were driving down the interstate last night I could have sworn it went away as RPM/oil pressure went up but, in the driveway it seems to do it at all RPM. Maybe it was just road sound covering it up. I changed the bearings last year while I was doing the trans just as an added measure to try to get more miles out of it while I was down there. I seem to remember that I would have done the oil pump but, they have some design that wraps around the crankshaft?

I'm thinking about having her take it to the local dealer just to see if they can quickly diagnose it and give us an estimate. I learned with my Freightliner when it had a wiring problem that it's sometimes better to pay a higher hourly rate but, pay for fewer hours when someone can go right to the problem.

 

[CDR]

Ron,

3.0L is a mitsu engine. 3.3L and 3.8L are Chryslers. The 3.0L mitsu uses a timing belt versus a chain for the 3.3/3.8.

Sounds like excessive bearing clearance. Put your stethoscope on the oil pan with it running to hear the knock. Has it ever been run out of oil? If so, rod bearing(s) and crank could be hurt. 3.0L mitsu motors LEAK a lot of oil unfortunately.

It COULD be a water pump (water pump is timing belt driven--coolant leaks are obvious out of the plastic timing cover) bearing based on the fact you said the noise was above t-stat housing. But, hard to diagnose over the computer.

Might want to listen to the bottom end real good again....

Keep us posted ....

 

[Jenn]

I just hate tracking down noises, I'm not sure if it's from being around racing engines so long or if it's just something with the tone but sounds sometimes seem to be coming from one area but really coming from another area.

I've had the lifter tapping sound on my car (3.3) for a few months, it goes away after it warms up. I need to replace the valve stem seals on mine soon too.

 

[Nitrohaulic]

Okay, I've got better clues. It's definitely not bottom end as I put the hose/stethoscope against the oil pan first thing and get nothing. Like I said, I changed rod and main bearings when I didn't even need to.

It's not a tapping like "tappets" (LOL), as in it's not a steady valvetrain-like tapping like one for one per revolution (or every other revolution, I know, it's a four stroke). It really is a rattling.

At idle the rattle starts out mild, then peaks to a loud rattle, then tapers off to a quiet rattle, goes silent for an instant, then starts the cycle all over again. I timed it with my stop watch and over and over again I got right at 1.5 seconds per "rattle cycle." I'm wondering if that's about how much time it might take the belt to make one revolution? (edit. Now that I'm thinking about it, it seems like it would make several in that time) I was guessing that it might have a chain instead of a belt but, whichever it has, that's where my suspicions lie.

I'll see if any of you are familiar with this engine before I decide whether to start taking things apart to look for it or take it to a dealer. I'm just betting it's something that might be common to this engine and that someone familiar with them might be able to say "That sounds like this that I've run into before with those."

 

[Jenn]

Okay, I've got better clues. It's definitely not bottom end as I put the hose/stethoscope against the oil pan first thing and get nothing. Like I said, I changed rod and main bearings when I didn't even need to.

It's not a tapping like "tappets" (LOL), as in it's not a steady valvetrain-like tapping like one for one per revolution (or every other revolution, I know, it's a four stroke). It really is a rattling.

At idle the rattle starts out mild, then peaks to a loud rattle, then tapers off to a quiet rattle, goes silent for an instant, then starts the cycle all over again. I timed it with my stop watch and over and over again I got right at 1.5 seconds per "rattle cycle." I'm wondering if that's about how much time it might take the belt to make one revolution? (edit. Now that I'm thinking about it, it seems like it would make several in that time) I was guessing that it might have a chain instead of a belt but, whichever it has, that's where my suspicions lie.

I'll see if any of you are familiar with this engine before I decide whether to start taking things apart to look for it or take it to a dealer. I'm just betting it's something that might be common to this engine and that someone familiar with them might be able to say "That sounds like this that I've run into before with those."

I have a 'tappets' problem. I was just hesitant to use that word cuz I thought I'd come up with it on my own and it was my own word. lol.

Now that I have more information, I'll try and look it up on IATN, I think it stands for International Automotive Technician Network, which is basically a network that techs can get together and put hard to solve things on there to see if other techs have run into the same sort of problem. Usually the techs can point you into the right direction.

I will see if I can log in today, I don't have the password here and I think it's one of those websites that is registered to a specific computer. I'll let you know.

 

[Nitrohaulic]

Thanks a bunch. I'm heading out and don't know how WiFi access will be this week, so I'll call you in a few days if nothing else. Yeah, it's definitely louder near the front of the engine (passenger side). I put my high tech stethoscope there and it gets loud. Thanks again.

 

[Don]

You sure it's not the rocks in yer head?

oil pump shaft drive perhaps?

 

[Nitrohaulic]

You sure it's not the rocks in yer head?

oil pump shaft drive perhaps?

LOL, watch out there Whitey.

If I'm remembering correctly, a year ago when I did rods and mains I wanted to do the oil pump but, I think it's some wrap around the crankshaft snout deal that does away with the drive shaft. I think I was going to have to take the whole front of the engine apart to do it and said to heck with it.

 

[CDR]

I'll see if any of you are familiar with this engine before I decide whether to start taking things apart to look for it or take it to a dealer. I'm just betting it's something that might be common to this engine and that someone familiar with them might be able to say "That sounds like this that I've run into before with those."

Accessing the timing belt/water pump on a 3.0L is not hard, but if you aren't well versed in removing and installing timing belts, it's best left to a professional shop that you trust. Just a tooth off on a timing belt can create huge driveability problems.

I don't know if Jenn looked, but I did look on iATN today. Most of the engine noises on the 3.0L's that folks were reporting were valve-train noise. Based on your description, it doesn't sound like that is your problem. Have you listened to the valve covers? Taken the oil cap off with it running, and listened in there?

Back when I worked at Chrysler, the early 3.0L's had a big problem dropping valve guides--causing excessive oil consumption among other things.

Good luck, Ron. Call me at my shop to discuss further if needed. 303.660.0522, ask for Chris. I've only succesfully diagnosed a car over the phone once, when a lady with a Subaru called with a crank no-start. I told her to hold the phone up to the engine while she cranked. Sounded like it had no compression--I said timing belt. Towed it in, timing belt broke, banged 6 valves.

 

[Jenn]

Accessing the timing belt/water pump on a 3.0L is not hard, but if you aren't well versed in removing and installing timing belts, it's best left to a professional shop that you trust. Just a tooth off on a timing belt can create huge driveability problems.

I don't know if Jenn looked, but I did look on iATN today. Most of the engine noises on the 3.0L's that folks were reporting were valve-train noise. Based on your description, it doesn't sound like that is your problem. Have you listened to the valve covers? Taken the oil cap off with it running, and listened in there?

I did look and found mostly valve train noises, included an upper engine noise coming from the thermostat housing area which was a cracked rocker. I also found a crack in the TC I'd e-mailed them to Ron last night but they came back.

 

[Nitrohaulic]

E-mails came back? Hope not.

I'm getting in later than usual this week due to hauling a friend's funny car body down to South Carolina. Gonna try to spend Sunday digging in and seeing what I can find. I'll take the valve covers off first since that's the quickest and easiest but, I'm thinking it's in the timing belt(s) or gear(s). Will post my findings.

 

[Jenn]

I had to transfer all my e-mails to a different account as my sister threatened to sue me if I didn't stop using my other account.

 

[Nitrohaulic]

Chris Andrews nailed it with his "It COULD be..."

Her continuing to drive it has made the problem get bad enough to easily find. Now it's dripping water off the crank pulley and after going to some online diagrams, it turns out the water pump is at the front of the engine and in the center, just under the thermostat housing (where my rattling was the loudest) and behind the cam belt, which is what turns it. (and, you CAN'T even see it with a flashlight)

What a design. Water goes into the back of the block through one big O-ring sealed pipe that runs all the way through the engine, sealing to the back of the water pump with another O-ring.

Oh well. Found out the timing belt should be changed at 60,000 but, many people run them till they break, then just pay the tow and repair since there's no piston-valve interference on these. At least I can take care of both for less than $100 parts and what I'm sure will be a "fun" day changing them.

 

[Jenn]

Well, I'm glad you got it figured it out even if I wasn't right!

Did you get a lot of water in the oil?

 

[Nitrohaulic]

Haven't noticed any water in the oil. Apparently whatever clearance the water pump was developing was making some kind of harmonics type vibration. Maybe we can get 200,000 out of this old thing, yet. Whew! I thought I'd lost my cheap...ahem..."cost effective"...nostalgia funny car support vehicle.