98 GT - Buzzing/quiet grinding under dash 2500 rpm+ after new heater core


Jun 17, 2013
Reaction score
Hello! I just got a new heater core installed, however, when I drive around and the engine goes above 2500 or so RPM a buzzing/grinding noise comes from under the dash... From under the hood there is no noticeable sound. I took off the front vent/radio bezel and the stereo but I still cannot pinpoint where the sound is coming from... I would return it to the guys that did the heater core but they are located in a different state as I go to college away from home and got it repaired over the break. Any ideas on where the sound could be coming from?

Any help appreciated! I don't want to have to take off the whole dash...


Active Member
Jan 18, 2013
Reaction score
Make sure heater core isn't leaking .

Make sure hoses aren't plumbed backwards

Make sure fan isn't rubbing on the core

I'm not sure it there's a panel make sure it isn't touching or vibrating if there is .

Go under the hood and take a pair of vice grips and clamp the heater core hose and stop the flow and see if the noise goes away , if it does you got a faulty heater core . New parts can be bad as well .

Just some ideas hope it helps

God bless you

Sent from my iPhone using Tapatalk


Well-Known Member
Jan 1, 2014
Reaction score
^ if none of that works, it may be the dashboard rattling. I've never done one on a mustang, but I know on the older Taurus the dash has to come off, the metal clips can get bent that hold the dash panels in place causing a weird sounding vibration. I'm guessing if it's a buzzing sound that this is it


Post Whore
Oct 9, 2009
Reaction score
Evansville Indiana
This reminds me of my old room mate/friend I lived with for a few years. He fills the tank and that is about as far as he goes to work on his car so for a month or so he kept telling me that he wanted me too take a look at his car as he had a rattle at 2200 rpms. Not 2100, not 2300, but at exactly 2200 - he kept telling me that for about a month I think when he thought about it. He normally only came home when the bars closed so the first day I was out in the driveway and he woke up at the crack of 11 he asked if I could take a look at it. He started the car and showed me and he was right, only at 2200 rpms.... So he pops his hood, as he goes to grab the prop-rod I tell him to stop, I see the problem. He is still holding the hood and now looking in confusion that I spotted it so quickly. I laughed my ass off as all it was, was the prop rod was not latched under the hold-down and you could see spots that it had rubbed through the paint from rattleing between the hood/core support. If he would have just popped the hood up and stuck his head under it a month ago he would have fixed it himself with out even knowing.

get under the dash and tighten up every screw/bolt you can see. Take some wire ties with you and tie up any loose wires that are hanging down. Grab/pull/tug on anything you can see too see if its loose and try to figure out a way to tighten it up. see if you can reach any loose wires or if the back of the deck is able to move by sticking your hand up into the dash by the accelerator and the glove box.

Latest posts

Forum statistics

Latest member
All Da Beanz Racing