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Other Leak Detection Applications (Cont.)
Exhaust Leaks
Escaping exhaust gases can be very dangerous to the occupants of a vehicle yet these repairs are
neglected — but so easy to find with the MotorVac Cool Smoke.
1. Put the vehicle on a lift to expose the underside. With the engine turned off, simply insert the exhaust
adapter cone into the tail pipe of the vehicle being tested. Insert the smoke supply line nozzle into the
exhaust cone’s hose opening. On dual exhaust systems ensure that each tail pipe is plugged.
2. Look for the smoke exiting wherever there is a leak.
3. Even though exhaust leaks are very easy to find with MotorVac Cool Smoke, here are three helpful tips to
make finding exhaust leaks even easier:
• It is best to test a cold exhaust system rather than a hot one.
• The catalytic converter may consume some of the smoke. But most importantly, many small exhaust
leaks are only visible on a cold exhaust system due to ‘thermal expansion’.
• Seal off the vehicle’s intake system in order to achieve proper system pressure in the event both an
intake and exhaust valve are open in the same cylinder at the same time.
EGR Valve Leaks
The exhaust gas re-circulating (EGR) valve is at the heart of the emission control system. Since the EGR
valve operates in such a hostile environment it is susceptible to leakage. During a normal test for vacuum
leaks, the EGR valve will be exposed to smoke and may show leaks at the seat, diaphragm, or even the
base gasket. If smoke is seen exiting the EGR valve, disconnect the vacuum supply line and introduce
smoke directly into the valve. This will verify if the diaphragm is leaking, or if the valve is leaking at the seat.
Smoke may also be used to check the EGR ports for restriction. Open or remove the valve and introduce
smoke through the tail pipe to verify that these ports are open.
TIP -
Testing the EGR Pintle Shaft: This will help you diagnose a good or bad EGR valve and
other “metered” leaks.
1. Do not cap off any part of the engine – leave it in normal operating state (but NOT running). Insert the
MotorVac Cool Smoke supply hose into a direct vacuum manifold source, such as a brake booster hose
or PCV. Turn the tester ON. Watch for smoke to escape from the EGR valve. If you see a lot of smoke,
move on to the next step.
2. Cap off the intake using one of the cap plugs supplied with the MotorVac Cool Smoke.
Insert the exhaust cone into the tailpipe. (The hose on the exhaust cone should be plugged with the
cap plug provided.) Now that the system is sealed, press the smoke button and watch for smoke.
A small amount of smoke indicates an acceptable EGR valve.
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