This page is about a Saturn rattling noise that could drive you completely insane. A friend of mine purchased a 95 Saturn SL1 that he planned on using as a commuter car.
He got a great deal and the vehicle had low mileage. To my surprise it got about 22 miles per gallon on the highway. This was about double the mileage he was getting from his Ford expedition.
Unfortunately, this Saturn had a rattling noise that could drive you completely crazy. The condition was documented in a technical service bulletin, but I didn’t come across it until I spent several hours trying to track it down.
The noise seemed to come from inside or behind the instrument panel. The rattle peaked when letting off the gas pedal at 1500 RPM’s in any gear.
However, the sound was most evident when cruising through a parking lot at a slow speed. And when letting off of the gas to go over a speed bump the noise could literally wake the dead. In my sharper days I would have realized that manifold vacuum peaks at the same time as the condition.
Rattle Noise Diagnosis
But it truly sounded like something was loose behind the instrument panel. So I disassembled it dash and pulled the instrument panel and secured all the wiring harnesses, and anything else that could make a rattle noise.
I also insulated the plastic instrument panel with some foam rubber strips, where it mounted in the plastic dash. After putting the Saturn SL1 back together and taking it for a road test the noise was still there.
Pressing on, I realized that directly behind the instrument panel on the fire wall side is the vacuum assisted brake booster. Inspection of the unit didn’t yield any problems.
However, when the vehicle was in park, if you revved the engine the noise disappeared. Finally I realize manifold vacuum is at its peak at closed throttle and fluctuates when you open the throttle.
Technical Service Bulletin for Saturn Cars
This technical service bulletin that I found directly related to the rattling noise that was occurring. The TSB covers all Saturn models from 94 to 97 that experience this problem.
The brake booster check valve is the Saturn rattling noise. The check valve is designed to store a vacuum charge in case the engine stalls, you will still have power-assisted brakes for a few pumps.
The brake booster check valve was operating correctly and did store the vacuum with no leaks. The problem is that when manifold vacuum fluctuates at the valve, the ball inside violently rattles.
The noise is transmitted through the brake booster and to the firewall, which is directly on the other side of the instrument panel.
The original brake boosters check valve with the problem is black in color. The replacement check valve is brown in color.
If you have this condition, and you find a black check valve then this will need to be replaced with the updated part.
The official Saturn part number is 21012702. The replacement part comes with a new grommet, and some silicone grease plus complete instructions on how to install it.
This is a very simple do-it-yourself auto repair, but you do want to follow the instructions since it’s a safety concern that directly relates to the operation of the power brakes. If in doubt, let a professional mechanic install it, because they might do it for free as a good will gesture?
Auto repair news never stops. There are new technical service bulletins showing up every day. This next link takes you to more auto repair news The next link shows you where to get technical service bulletins and auto repair procedures for your specific car or truck. I put together a video and some information about the best online car repair manuals.
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