Vacuum leak? - LotusTalk - The Lotus Cars Community
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post #1 of 13 (permalink) Old 05-01-2019, 01:45 AM Thread Starter
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Vacuum leak?

Hi all,

During a track session yesterday, my Exige threw a little fit, and I wanted to run this by you guys.

Here are the symptoms:
  • Does not idle
  • Runs rough, does not like to maintain speed.
  • Seems to run OK if I hold the accellerator down a bit
  • When I let go of the pedal, there ia loud sound I have never heard before, not the typical whistle of air escaping.
  • Brakes are almost gone (should be a dead giveaway for vacuum issues)

and last,

I decided to drive it home, a 40 minute drive on the back roads. The acr still runs and there were no changes in behavior.
when I got home and got out of the car, however, I noticed that the exhaust were almost glowing. In fact, so hot that the aluminium license plate is now discolored, and I think a part of the clam (by the U bend) is discolored as well.

Plan is to tilt the clam today and start looking, but I wanted to ask.... Has anyone had a problem like this before, and does anyone have an idea as to where I hsould start looking? ?

Understeer is when you hit the wall front first.
Oversteer is when you hit the wall rear first.
Horsepower is how fast you go when you hit the wall.
Torque is how far you take the wall with you.

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post #2 of 13 (permalink) Old 05-01-2019, 12:01 PM
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you have the stock cat? Maybe its blown out.

** save ~10 lbs gain 1 hp ** EQ: Y=(190*X) / (1984-X) where Y is (HP) and X is (lbs)

'07 Lotus Exige S310


WTC 2
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post #3 of 13 (permalink) Old 05-01-2019, 07:48 PM Thread Starter
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Quote:
Originally Posted by shay2nak View Post
you have the stock cat? Maybe its blown out.
I forgot to mention... No error codes.
A blown cat would give error codes, wouldn't it?

Understeer is when you hit the wall front first.
Oversteer is when you hit the wall rear first.
Horsepower is how fast you go when you hit the wall.
Torque is how far you take the wall with you.

Visit my photo gallery
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post #4 of 13 (permalink) Old 05-03-2019, 10:02 AM
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Quote:
Originally Posted by Iveria View Post
I forgot to mention... No error codes.
A blown cat would give error codes, wouldn't it?
I would think so. Just did a search and looks like it would throw a 0420.

** save ~10 lbs gain 1 hp ** EQ: Y=(190*X) / (1984-X) where Y is (HP) and X is (lbs)

'07 Lotus Exige S310


WTC 2
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post #5 of 13 (permalink) Old 05-03-2019, 11:15 AM
He's on fire!
 
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Sounds possible to be a vacuum leak to me. There are a couple of videos on the internet on detecting leaks. The "easy stuff" would be checking your IC couplers, especially if you've removed them for any reason recently.

"Give a man a match, and he'll be warm for a minute, but set him on fire, and he'll be warm for the rest of his life."
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post #6 of 13 (permalink) Old 05-04-2019, 03:12 AM Thread Starter
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Found the culprit, and is was no no way a small, hard to find leak:

The pipe that runs from the head to the throttle body had come loose and fallen out:



(I am quite sure that I found the problem, or at least one of them. I put it back in place and the engine idles and stuff again)

So now I need to figure out how to make this stick again. Not welding it as that would requre taking most of the engine intake apart..

Any recommendation for a Loc-Tite or similar product to be used in a hot and oily environment?
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Understeer is when you hit the wall front first.
Oversteer is when you hit the wall rear first.
Horsepower is how fast you go when you hit the wall.
Torque is how far you take the wall with you.

Visit my photo gallery
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post #7 of 13 (permalink) Old 05-04-2019, 07:08 AM
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Quote:
Originally Posted by Iveria View Post
Found the culprit, and is was no no way a small, hard to find leak:

The pipe that runs from the head to the throttle body had come loose and fallen out:



(I am quite sure that I found the problem, or at least one of them. I put it back in place and the engine idles and stuff again)

So now I need to figure out how to make this stick again. Not welding it as that would requre taking most of the engine intake apart..

Any recommendation for a Loc-Tite or similar product to be used in a hot and oily environment?
I realize this may sound tacky, but JBweld. It is petrolium resistant as long as all is properly cleaned and should hold up to the heat just fine...but I am not an expert on that.

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post #8 of 13 (permalink) Old 05-04-2019, 07:32 AM
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You mean the PCV hose?

Should have hose clamps......

I just installed catch cans and found that one of the hoses is an odd size, like 14mm 9/16" so if it was replaced with a chunk of heater hose that might make it fall off
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post #9 of 13 (permalink) Old 05-07-2019, 12:28 PM
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That part (resulting leak) caused the exhaust to glow?! That's why I thought the cat failed and was blocking the exhaust path.

** save ~10 lbs gain 1 hp ** EQ: Y=(190*X) / (1984-X) where Y is (HP) and X is (lbs)

'07 Lotus Exige S310


WTC 2
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post #10 of 13 (permalink) Old 05-07-2019, 01:05 PM
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Quote:
Originally Posted by shay2nak View Post
That part (resulting leak) caused the exhaust to glow?! That's why I thought the cat failed and was blocking the exhaust path.
Yeah it would be super lean, really hes lucky he didnt blow the engine. Although as I learned this weekend, it may still fail in the next few sessions as one of the rod bearings can get weakened by detonation then fail as you are finishing the maybe winning lap for the day............
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2007 Exige S with almost every track mod...
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post #11 of 13 (permalink) Old 05-07-2019, 01:37 PM
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Whats odd to me about this thread, is that on my car that line is very easy to detach as well. I can pull it right out of the throttle body.... but I've never "found" it out.

I'm not sure if its even worth messing with too much, if its standard state on all cars. Maybe you just did something to knock it loose?

"Give a man a match, and he'll be warm for a minute, but set him on fire, and he'll be warm for the rest of his life."
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post #12 of 13 (permalink) Old 05-07-2019, 01:49 PM
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Quote:
Originally Posted by jds62f View Post
Whats odd to me about this thread, is that on my car that line is very easy to detach as well. I can pull it right out of the throttle body.... but I've never "found" it out.

I'm not sure if its even worth messing with too much, if its standard state on all cars. Maybe you just did something to knock it loose?
Maybe his valve cover has a fair bit of pressure in it, mine does, and it blew off? weird though as it should always be in a vacuum on the TB side. Put some hose clamps on yours if you're worried. Im surprised they don't have them from the factory. I took mine off almost as soon as I got the car and saw the intercooler full of oil.

2007 Exige S with almost every track mod...
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post #13 of 13 (permalink) Old 05-07-2019, 03:39 PM
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Quote:
Originally Posted by kfennell View Post
Maybe his valve cover has a fair bit of pressure in it, mine does, and it blew off? weird though as it should always be in a vacuum on the TB side. Put some hose clamps on yours if you're worried. Im surprised they don't have them from the factory. I took mine off almost as soon as I got the car and saw the intercooler full of oil.
I'm suggesting that if all cars have this line loosely connected, and OP has a chronic issue of this line blowing off, that JB weld or whatever is likely fixing the symptom, rather than fixing the problem.

"Give a man a match, and he'll be warm for a minute, but set him on fire, and he'll be warm for the rest of his life."
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