|01-23-2011, 02:09 PM||#1|
Join Date: Jan 2011
Known vacuum or exhaust leaks
1997 SL2 1.9 DOHC, 5 spd., 175k mi and still going. Just replaced the ECTS and yes it was cracked. Attempting to get the best mileage possible and the recent 20 mpg. brought me here. My question for today is this. Is there a known vacuum or exhaust leak in the general area of the power steering pump on these vehicles. The sound I am hearing is only apparent when revving the engine. Other wise, all seems to be normal engine noise.
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|01-24-2011, 03:43 AM||#2|
Join Date: Dec 2005
Location: Brookline, MA
Re: Known vacuum or exhaust leaks
Well, they sound different. If you're sure it actually is a leak, it could be a vacuum leak at the MAP sensor. That's on the end of the intake manifold right next to the ps pump. It could also be a vacuum leak at the number 1 intake runner (where it meets the head)--under the ps pump. Test around that area with brake-cleaner or carb-cleaner. See: http://www.youtube.com/watch?v=mYa8rcHeN3A
An exhaust leak will sound different. If it's in the manifold runners or where the manifold meats the head, it'll sound like a tapping noise, the frequency will depend on the rpm (higher rpm, higher frequency). The volume will depend on the engine load (higher load=louder). If it's down-stream, where it's one single pipe, it'll just sound like a louder exhaust.
One easy way to test for an exhaust leak is to do an MMO or similar piston soak (search, if you don't know what that means). When you restart it, have someone block the exhaust at the back with their hand or a rag or something to add some back-pressure (don't try to block it completely, just enough to create some pressure). You should be able to see smoke at the exhaust leak. (The person in back will get lots of smoke--be sure they're prepared--might want to hold their breath.) If it's cold enough, the steam from a cold start might be enough to see it without doing the piston soak.
High compression build: .033" shaved/ported head, flat-faced valves; gen3 rods, pistons, tie-plate; OE header, custom CAI, SDA street cams with adjustable sprockets, WBO2, SAFCII, LSD. ASE A1-A8+L1
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