Car Mechanics (UK) EXHAUST RENEWAL
It is advisable to replace all rubber mounts, as the existing ones may be worn, which places the exhaust under extra strain. You may need to provide evidence that they were replaced if you make a warranty claim later.
Unlike the exhaust pictured in Steps 1 and 2, many newer cars feature a one-piece system for ease of manufacture. You do not need to replace the entire exhaust if one section is damaged, because…
Also check the condition of the heat-shields and their fastenings. Should they be damaged, or missing, you risk a vehicle fire, especially on diesel models that are fitted with DPFS.
Exhaust leaks are not always as obvious as the one pictured. Small holes may be able to be bandaged, but this does not buy much time – the entire section will have to be replaced sooner, or later.
Inspect the entire system carefully before ordering any parts. You may find that corrosion has spread from one section to another, such as on this joint that has fused the two sections together.
Here, the clamp was so rotten that it needed to be cut off. However, because the joint was severely corroded, an easier and longer-lasting repair was effected by cutting off the mid-section end with an angle grinder.
Alternatively, make your own reference marks, by taking measurements from the new exhaust system. Start the removal process, by spraying lubricant (maintenance spray, or soapy water) over the rubber mountings.
…the original exhaust may have marks (as highlighted) to denote the point at which the exhaust can be cut and a replacement section spliced in. Pictured is a 2006 Skoda Octavia 1.9 PD diesel backbox to middle section.
This will make it easier to separate the exhaust system from the bodywork. Professionals use a dedicated tool for this; we have seen cheap versions on sale for as little as £15 – a worthwhile purchase for occasional users.
Alternatively, you can cut the bracket from the exhaust system. Once the working area is clear, you can pull the mounting away by hand. Check that the bracket, welded to the body, is neither coming away, nor weakened by rust.
A suitable rubber mount removal tool (such as the Laser 5158) helps to reduce the risk of skinned knuckles, or damage to the rest of the exhaust system, if trying to manipulate the old system using force.
Striking too hard risks deforming the metal, making it harder to separate the pipes. Manipulate the sections to split them; if they do not budge, you might have to resort to the technique described in Step 3.
Before removing the section completely, check if any removable brackets are present that will hinder your ability to dismount the exhaust from the car.
These brackets tend to be straightforward to remove, because they usually are held to the body by nuts, which screw into captive threads that are welded to the floorpan.
Should you need to replace another section, the technique is the same: remove the rubber mounts and clamps, then manipulate the exhaust from the car. Note the slightly different clamps used on this Skoda’s mid-section.
Establish how the front section is mounted to the car and detach any wiring, sensors, or pipes from the exhaust; this diesel Skoda lacks all of these. You may also have to dismount the engine undertray.
Once freed, manipulate the old exhaust section out from beneath the car, taking care not to damage any adjacent parts and paintwork. Old exhausts can be disposed of as scrap metal at your local household recycling centre.
Where the joint consists of one section of exhaust fitting inside another, unbolt, or cut off the clamp. Corrosion can make the system tricky to separate, but several taps with a hammer may help free the parts.
Removing the front exhaust section tends to be trickier, because of reduced access. You may find more elaborate mounts, such as this bracket assembly, secured by several bolts to the subframe.
This front section fits directly to the turbocharger with a stainless-steel V-band. Alternatively, you may encounter nuts and bolts, which might be reluctant to unscrew and could snap off.
Look for further brackets that are either fixed to the exhaust, or might otherwise be a hindrance as you try to withdraw it. Remove and retain any parts that are in the way for later refitting.
Pictured is the point at which the turbocharger and exhaust system mate. Check that the flange is in good condition and consider giving it a clean with a wire brush, but take care that no particles enter the housing.
Ask your supplier if the front V-band, such as the one pictured, should be replaced. Klarius told us that this Skoda’s clamp was in serviceable condition and could be reused without affecting its warranty.
Manipulate the front pipe from beneath the car. As it tends to be the hottest part of the system, corrosion tends not to be a problem, but the flexible sections can leak after years of vibration.
As it’s easy to make errors when ordering exhaust parts, compare a replacement system with your original, by laying them on the floor side-by-side.
Locate any mounting clamps (see inset pic) and manipulate the new exhaust system into position. You might need the help of an assistant. Never add assembly paste upstream of a catalytic converter.
When replacing a complete system, work from the front end of the car to the rear. This front pipe has its gasket replaced, which locates within the exhaust and fits between the pipe and turbocharger (see Step 23).
It is likely that you find minor differences, such as the shape of this bracket. However, provided that their ends finish in the same dimensional positions, there should be no need to worry.
Discard the old parts and fit new rubber hangers onto the car mounts beneath the car. To make fitting easier, lubricate the rubbers before attaching the new exhaust system.
Ask your supplier for advice on replacement clamp sizes, where you are fitting a new section onto a one-piece exhaust. The clamp size is marked on its side.
The pipes should fit together neatly, being neither too tight, nor too loose. Repeat Step 33 with your exhaust assembly paste, remembering that it must be used sparingly.
Manipulate the back-box to ensure that it not only clears any components beneath the car but that it is also aligned centrally with the pipe cut-out in the rear bumper skirt.
Start the vehicle's engine and allow it to run for five minutes, prior to embarking on a test-drive. The exhaust should be relatively silent, with no evidence of gases escaping, and the engine management light should not be illuminated.
Fit all brackets and mountings to the exhaust, prior to locating and tightening the clamp bolts. Then, double-check all bolts for tightness and refit any removed parts.