A heat shield is a part that is provided to protect the surrounding underbody parts of the vehicle from heat dissipated by the engine and exhaust system. But these heat shields would come loose over a period of running.
The main reason for the Subaru heat shield rattle is either the rusted heat shield losing its strength or the mounting hardware used to bolt the heat shield becoming loose and making a rattling noise due to vibration.
One of the best solutions to address the heat shield rattling issue in Subaru involves using hose clamps to tighten the heat shield over the exhaust pipe in combination with using steel wools to fill the void between the heat shield and the exhaust pipe. This completely restricts the heat shield movement thereby stops the rattling noise.
Are you facing the issue of Subaru heat shield rattle and thinking of why the heat shield is required in your Subaru or can it be removed and what are the probable solutions for the rattling noise? Then you are at the right place. Stay tuned!
Table Of Contents
Why heat shield is required?
Typically, the heat shield is wrapped around the exhaust pipe and catalytic converter where it is located or routed close to the vehicle underbody floor and bodywork to drive away the exhaust system heat.
These are the areas where the occupant comes close to the vehicle and the heat shield would provide comfort to the occupant by preventing radiant heat.
Heat shield also plays an important role in preventing dry grass fire incidence beneath your car which results from vehicle heat source like catcon coming in contact with long dry grass when you park your car after a long ride.
Heat shield when wrapped around the catalytic converter (catcon) also provides good thermal energy which is necessary for chemical reactions and optimized catcon function.
Due to heatshield, the catcon would build up heat soon and it shall stay hot for a longer time thereby helping in optimizing the catcon and engine performance.
Step to identify loose heat shield
When you suspect that your Subaru heat shield rattles and makes an annoying noise, it is essential to confirm whether the source of the rattling noise is a heat shield or something else.
- First of all, allow to cool the vehicle first, since the exhaust pipe is always hot during driving and immediately after parking the vehicle.
- Jack up the vehicle and look for the exhaust pipe routing and heat shield
- Smack all along the length of exhaust pipes with a palm or any wooden piece, especially at the heat shield fitted areas.
- If the heat shield is rattling then probably you would notice that the heat shield moves and makes a tiny rattling noise instead of a solid thud and it may be fitting loose over the exhaust pipe
- If none of the exhaust system parts is fitting loose, then look for holes or cracks on the exhaust pipe.
Subaru Heat Shield Rattle? 4 Probable Reasons And 7 Solutions To Fix it!
Probable Reasons For Subaru Heat Shield Rattle Issue
Loose fasteners
When the vehicle covers some mileage, due to the exposure of the heat shield to continuous vehicle vibrations and road-induced excitation forces, the heat shield vibrates and the mounting hardware becomes loose and the heat shield starts rattling.
You may hear to huge rattling noise from the heat shield in your Subaru especially at certain engine RPMs depending upon the road excitation frequency.
The loose heat shield Ensure that you tighten the hardware at regular intervals during the periodic maintenance schedule.
Wear and tear
Often the heat shield is the lowest part of the vehicle and it can easily come in contact with stones and gravel from the ground, resulting in wear and tear of the heat shield which makes the Subaru heat shield rattle.
Rusting
As the vehicle ages and covers certain mileage, the heat shield is exposed to heat and different chemicals from the environment which makes the heatshield prone to corrosion.
Once the heat shield corrodes, it gets subjected to more wear and tear and loses its thickness.
This makes the heat shield fit loose and the Subaru heat shield rattles thereby.
Holes on exhaust pipes
Since the exhaust pipe is subjected to unburnt fuel and high temperature, there are chances of corrosion of the pipe. When the extent of corrosion increases, you may see the pipe getting shipped off or holes in the exhaust pipe.
When the engine emissions pass through these chipped-off portions or holes, it makes a rattling kind of noise which people mistake for a heat shield rattle.
Moreover, when the exhaust pipe is very hot and water gets splashed up from the road, sudden quenching makes the pipe brittle and it gets cracked locally.
Solutions To Fix The Subaru Heat Shield Rattle Issue
Hose clamps
If you notice that the heat shield is rattling and is fitting loose over the exhaust pipe, then use metallic worm gear hose clamps to tie the heat shield to the exhaust pipe.
We may need to use 2 or more hose clamps if the boundary to wrap around is more. Use ratchets for tightening the hose clamps. Tight the clamps once a year as they may get loose over some time.
SS wires
Alternately you can use SS safety wires to wrap around the heat shield and the pipe. Crimp the ends of SS wires to tighten the wire and to ensure that the heat shield fits tight against the exhaust pipe to stop the rattle.
Steel wools
If you do not have hose clamps, then you may use steel wool to fill the void between the heat shield and exhaust pipe. This void is what allows the rattling of the heat shield.
Use a screwdriver to wedge the steel wool at the gaps between the heat shield and pipe or underbody floor.
You can use steel wool in combination with hose clamps to ensure that the steel wool is retained in the voids even when it is subjected to vehicle vibrations and stones and gravel from the ground.
Spot fix heat shield
If the heat shield is corroded and thinking of replacing it, then you can think of using peel and stick kind of flexible spot-fix heat shield foil with strong adhesive backing as an alternate option. Replacing the heat shield with a new one would be a more expensive affair.
Fiberglass exhaust wraps
If you use steel wools there are chances of it disintegrating over time depending upon how tightly you are packing the steel wools between the heat shield and the exhaust pipe.
As an alternate option, you can use fiberglass exhaust wrap insulation which is more durable and less expensive than replacing whole heat shield.
This would serve the purpose if you are planning for heat shield replacement.
Rework on exhaust pipe
If you notice that there are holes in the exhaust pipe which is making a rattling noise then you would need to do patchwork by welding or brazing a small piece of sheet metal over the hole.
This would temporarily block the holes, but as the vehicle ages you may notice more such holes, and eventually, you may need to replace the whole exhaust pipe.
Urethane exhaust hangers
If the vibration is more in your Subaru vehicle which is causing that rattling noise at the heat shield interface with the exhaust pipe, then you can use stiffer urethane exhaust hangers to prevent the movement of the exhaust pipe.
The heat shield rattling noise can also be minimized by constraining the exhaust pipe which is connected to the heat shield.
Conclusion
Often, you may find the heat shield over the exhaust pipe close to the underbody floor or cabin work where if the heat increases, it may affect the occupant’s comfort.
People often drill a hole in the heat shield and use a metallic screw at the hole until it touches the pipe to tighten the shield, but there are chances of the screw falling & puncturing the other vehicle’s tire. Hence it is not recommended.
The heat shield has been provided for some purpose in your Subaru vehicle, hence do not remove the heat shield or cut them off to get rid of the rattling noise.
Instead, you may try using the hose clamps and steel wools to restrict the heat shield movement which causes rattling and enjoy quieter and smoother driving experience.
Happy Motoring!
References
https://www.subaruxvforum.com/threads/heat-shield-rattle.185483/
https://www.subaruforester.org/threads/2009-infamous-heat-shield-rattle-solved.813303/
https://www.subaruoutback.org/threads/exhaust-heat-shield-rattle-when-cold.540245/
https://community.cartalk.com/t/rattling-of-heat-shield/21942
