Vibration when heater is on

[jearwood]

I have a 2003 Infiniti I35 with 180,000 miles. A few days ago I suddenly felt and heard some vibration coming from the engine. I turned the heater off to listen for it and the vibration stopped. Turned it on, vibration started again. Aha! I thought. Blower motor. I removed the blower motor and hooked it up and turned it on, holding it by the base. I was surprised that it ran very smoothly. I disconnected the blower motor completely and left the blower motor out until I could pick up a replacement. Out of curiosity tonight when I was driving home, I turned the heat on (with the blower motor still detached) to see if I might get some heat through the vents while I drove. I didn't heat, but the vibration started again. I opened the hood and noticed the radiator was vibrating a lot when the heater (sans blower motor) was on, but not at all when off. Any ideas?

[MaximA32]

Hows the coolant level? Could be a problem with a clogged coolant line.

[jearwood]

With a cold engine the coolant is visible when I take off the radiator cap, so I think the radiator is full. The reservoir is empty though. I did have to have my radiator replaced a few months back. Not sure if that could be related or not.

[MaximA32]

Could be. When the car is cold, top off the reservoir to the "Full Cold" mark.

[jearwood]

I'll give that a shot. Thanks for the tip! I'll report back.

[jearwood]

Topped it off. It didn't work, but I did notice that the vibration seems to stem from the fans behind the radiator which are turning on when the heat is turned on, but stop when it's turned off. Maybe something threw one of them out of balance?

[confish420]

hey i have a 03 maxima se with 131k i get the same thing u get same vibration but it does it more in summer when the ac is on like 3 alittle on 2 but heat itts smooth. does it feal like dragging if u rev the engine alittle while its on ?