Strange sound after fixing radiator

[AirSpeed]

I pulled the radiator in my 72 GMC 4X4 350/350 yesterday to fix a leak, this morning I drove it and its making a really strange sound. It doesn't do it until I put it in drive and give it a little gas, it sounds like "tink ta tink tink tink" (that's the only way I can describe it) it doesn't seem to do it in reverse, only drive. It doesn't seem to increase with speed, just makes the same sound. I feel no vibrations, it goes down the road smoothly like always. I can't see anything hitting under the hood. If I hold the brake while in drive it makes the same sound, even when the trucks not moving. Any ideas?
Posted via Mobile Device

[passthebuck]

One of those straps that rad rebuilders use had broken loose on my rad & was bouncing back & fourth off the fan with a tink tink tink. Easy one to check...

[truckster]

I would check the fan shroud. When the truck is in gear, torque moves the engine slightly off-center. The effect can be greater if the motor mounts are worn.

That's the only thing I can think of right now.

[VetteVet]

Loosen the fan belt so the fan don't turn and start the engine. If the fan was hitting something you won't hear the noise anymore and can then look for where it is hitting. Putting it in drive does torque the engine and may be just enough to cause it to hit the shroud like Truckster said. You may just have to move the shroud slightly.

[AirSpeed]

Originally Posted by truckster

I would check the fan shroud. When the truck is in gear, torque moves the engine slightly off-center. The effect can be greater if the motor mounts are worn.

That's the only thing I can think of right now.

Thanks, I was thinking the same thing so I put the parking brake on and put it in drive, got out and pulled the throttle under the hood, I could hear the sound but the fan clears the shroud easily. It only takes a little gas to get it to sound. It's all clear under the hood, nothing seems to be hitting anywhere. It only does it in drive. At first I thought it was in the engine, like a bad bearing but it doesn't change with speed or RPMS and it doesn't do it in reverse. It's really cold out right now so I'll check further when it warms up. If you or anyone thinks of anything else I can look for let me know! Thanks again!
Posted via Mobile Device

[AirSpeed]

I drove it after I fixed and reinstalled the rad yesterday and it wasn't making the sound. It started this morning after I warmed it up and took off.
Posted via Mobile Device

[mrein3]

Originally Posted by AirSpeed

Thanks, I was thinking the same thing so I put the parking brake on and put it in drive, got out and pulled the throttle under the hood, I could hear the sound but the fan clears the shroud easily. It only takes a little gas to get it to sound. It's all clear under the hood, nothing seems to be hitting anywhere. It only does it in drive. At first I thought it was in the engine, like a bad bearing but it doesn't change with speed or RPMS and it doesn't do it in reverse. It's really cold out right now so I'll check further when it warms up. If you or anyone thinks of anything else I can look for let me know! Thanks again!
Posted via Mobile Device

Try this:
Find a safe spot. No kids, pets, walls, garage doors, etc. to run into or over.
Open the hood all the way and climb in the driver's seat.
Start the truck. One foot on the brake and one on the gas.
Put the truck in reverse and with your foot still on the brake bring up the r's a bit.
Repeat in drive.
Of course this only works with an automatic transmission.
You want the hood open so you can peek at the top of the air cleaner between the cowl and hood to see it move.

This is the old school way to figure out if you broke an engine mount. The torque from the engine lifts it one way in drive and the other in reverse.

I suspect you have a worn engine mount that only lifts the engine in drive. Even if the mount is fine the torque of the engine will lift it a bit. The light ticking you hear could be the fan just kissing the shroud. It may have only started because after messing with the radiator you slightly repositioned the shroud.

If you're running a manual transmission, maybe dab a little paint on the inside of the top of the shroud, go for a drive, confirm the tick tick tick noise, then check for paint missing.

If you're just kissing the shroud, loosen things up, lift it a touch, and tighten it back down.

If you did break a mount this tick tick tick isn't quite so quiet.

[AirSpeed]

Originally Posted by mrein3

Try this:
Find a safe spot. No kids, pets, walls, garage doors, etc. to run into or over.
Open the hood all the way and climb in the driver's seat.
Start the truck. One foot on the brake and one on the gas.
Put the truck in reverse and with your foot still on the brake bring up the r's a bit.
Repeat in drive.
Of course this only works with an automatic transmission.
You want the hood open so you can peek at the top of the air cleaner between the cowl and hood to see it move.

This is the old school way to figure out if you broke an engine mount. The torque from the engine lifts it one way in drive and the other in reverse.

I suspect you have a worn engine mount that only lifts the engine in drive. Even if the mount is fine the torque of the engine will lift it a bit. The light ticking you hear could be the fan just kissing the shroud. It may have only started because after messing with the radiator you slightly repositioned the shroud.

If you're running a manual transmission, maybe dab a little paint on the inside of the top of the shroud, go for a drive, confirm the tick tick tick noise, then check for paint missing.

If you're just kissing the shroud, loosen things up, lift it a touch, and tighten it back down.

If you did break a mount this tick tick tick isn't quite so quiet.

I did that earlier, it will make the sound in drive but not reverse. I put the park brake on, put it in drive, got out and manipulated the throttle on the carb and was able to hear the sound. The fan is clear.
Posted via Mobile Device

[AirSpeed]

Well I just got done checking the truck out, took it for a ride, did some business at the bank, started it back up and the sound is gone. Happy about that but can't help but wonder what was the cause. I love when my truck heals itself! Thanks for the suggestions, I'm still curious what it was so if this has happened to you let me know what you found! Thanks again!
Posted via Mobile Device

[Ol Blue K20]

Did you get some coolant on the belt, that can make the belt chatter (which sounds like a click) but will wear off and stop the noise.

[AirSpeed]

Originally Posted by Ol Blue K20

Did you get some coolant on the belt, that can make the belt chatter (which sounds like a click) but will wear off and stop the noise.

I may have when I pulled the rad out but I don't think it would cause it to only sound in drive, it was quiet in neutral and reverse. After I fixed the leak I filled the system with plain water and drove around to clean out the stop leak I had in there, when I went to drain the system and add coolant I found one of my wrenches sitting under the radiator, Im wondering if I left another tool under the hood that could have caused the sound and maybe it finally fell off onto the street somewhere. I think I'll follow my path and see if there's any tools laying on the street! I'm hoping it was something like that. Thanks!
Posted via Mobile Device

[Ol Blue K20]

Originally Posted by AirSpeed

I may have when I pulled the rad out but I don't think it would cause it to only sound in drive, it was quiet in neutral and reverse. After I fixed the leak I filled the system with plain water and drove around to clean out the stop leak I had in there, when I went to drain the system and add coolant I found one of my wrenches sitting under the radiator, Im wondering if I left another tool under the hood that could have caused the sound and maybe it finally fell off onto the street somewhere. I think I'll follow my path and see if there's any tools laying on the street! I'm hoping it was something like that. Thanks!
Posted via Mobile Device

possible, you'll be mad when you need it and it's missing

[AirSpeed]

Originally Posted by Ol Blue K20

possible, you'll be mad when you need it and it's missing

Yea, it will probably be a my new ratchet! If the sound stays away I won't care though! I better go check my tool box!
Posted via Mobile Device

[Ol Blue K20]

Originally Posted by AirSpeed

Yea, it will probably be a my new ratchet! If the sound stays away I won't care though! I better go check my tool box!
Posted via Mobile Device

Just do what I do blame it on the kids, it makes ya feel better!

[AirSpeed]

Originally Posted by Ol Blue K20

Just do what I do blame it on the kids, it makes ya feel better!

I would but they're all grown up and moved away! I still have a wife to blame though! It's all her fault! Damn women!
Posted via Mobile Device

[Joesjunk]

Its possible that your trans cooler lines might have been rubbing together somewhere

[AirSpeed]

Originally Posted by Joesjunk

Its possible that your trans cooler lines might have been rubbing together somewhere

That's a possibility, the PO mangled the trans lines, he must have cut them to pull the tranny instead of taking them out the right way, he also cut them up front to run them to a cooler. The guy used hose and clamps to patch them together. It's one of the last things I need to address. When I put the rad back in I had to re tie the hoses out of the way, maybe I stuck them in just the right place to make the sound.
Posted via Mobile Device