Thumping noise under my 98 vert

[LLC5]

Any car built after 16 Dec 1997, has the EBTCM between the radiator and the engine, so about half MY98 production and all 99-up have it in front. Only 97 and about the first half of MY98 have it at the rear.

Jane Ann...help us out here...do you hear that "thump" when you're on the brakes?

I wasn't aware of the production date split on '98 model year for the EBTCM location.

The "THUNKING" noise that I am referring to does not require the brakes to be used and happens at low speeds, and the only time I have heard it there was a problem with the system and had stored codes for either ABS or TC. Since she has multiple history codes relating to the EBTCM system it was just something to keep in mind.

[Hib Halverson]

I hadn't heard of EBTCM's making noise like that when the brakes are not applied, but I 'spose anything's possible and I don't have enough depth-of-knowledge on EBTCM faults to say, "It can't happen."

That said, my gut feeling is this noise is not related to the brakes.

Boy. Would I like to road test this car.

What might be a bit unnerving is if this car "...goes 'thump' in the night." If it was a moonless night, it'd be even more scary!.

[XLR8]

All good suggestions and questions guys. And thanks for your patience.

Hib... mostly when I've noticed it I've been driving slowly up the gravel road in front of my house and though I don't ride the brake, it is possible I've applied the brakes. As to whether I'm braking when it makes the noise, I can't say but I will pay attention to that tomorrow when I drive it.

I don't think it's popping in the speaker because I actually did have that issue a little over a year ago after a driver door repair and Kevin found the problem and fixed it. It is possible that something in the trunk is thumping but doubtful... but I'll check that too. Antenna is good... no problems there, I think.

BTW... my 98 replica build sheet from the NCM is dated 10/27/1997.

I wish you could road test it, Hib. I hate chasing an intermittent noise.

Kevin will be back at work after the holidays and I'll probably take it to him to put up on the rack and go over the entire underside with a magnifying glass.

Thanks again guys!

[LLC5]

I hadn't heard of EBTCM's making noise like that when the brakes are not applied, but I 'spose anything's possible and I don't have enough depth-of-knowledge on EBTCM faults to say, "It can't happen."

All I can come up with is that the system was possibly doing a self test and it aborts immediately because of the multiple fault codes, causing a thunk noise. This happened on two different vehicles (one of them being my own), the noise was intermittent and I was only able to hear it at slow speeds. I do know that after repairing the faults the clunking type noise was gone.