High pitched noise while driving, vacuum leak?
#1
Senior Member
Thread Starter
Join Date: Sep 2014
Location: Austintown, OH
Posts: 625
Likes: 0
Received 3 Likes
on
3 Posts
Year: 2000
Model: Cherokee
Engine: 4.0
High pitched noise while driving, vacuum leak?
2000 XJ Sport, 4.0 auto tranny.
I was test driving it yesterday and noticed that there is a high pitched poise coming from the engine. The moment you give it throttle it fades out for a second or two then comes back. The CEL is one but the owner says it was for an o2 sensor that hasn't cleared yet. Until I put a reader to it myself I won't know. But could the noise be a vacuum leak? And if it is, could it be throttle related since it goes away for a second then comes back when you push the throttle?
I was test driving it yesterday and noticed that there is a high pitched poise coming from the engine. The moment you give it throttle it fades out for a second or two then comes back. The CEL is one but the owner says it was for an o2 sensor that hasn't cleared yet. Until I put a reader to it myself I won't know. But could the noise be a vacuum leak? And if it is, could it be throttle related since it goes away for a second then comes back when you push the throttle?
#2
Junior Member
Join Date: Oct 2014
Location: Lawrence, MA
Posts: 34
Likes: 0
Received 0 Likes
on
0 Posts
Year: 1999
Model: Cherokee
Engine: 4.0L I6 HO
2000 XJ Sport, 4.0 auto tranny.
I was test driving it yesterday and noticed that there is a high pitched poise coming from the engine. The moment you give it throttle it fades out for a second or two then comes back. The CEL is one but the owner says it was for an o2 sensor that hasn't cleared yet. Until I put a reader to it myself I won't know. But could the noise be a vacuum leak? And if it is, could it be throttle related since it goes away for a second then comes back when you push the throttle?
I was test driving it yesterday and noticed that there is a high pitched poise coming from the engine. The moment you give it throttle it fades out for a second or two then comes back. The CEL is one but the owner says it was for an o2 sensor that hasn't cleared yet. Until I put a reader to it myself I won't know. But could the noise be a vacuum leak? And if it is, could it be throttle related since it goes away for a second then comes back when you push the throttle?
Could you describe the noise a bit more? A high pitched noise can come from multiple areas, but the type of noise can help narrow the search.
For example, a high pitched squeal could be something like a loose belt, or maybe a spun bearing
A high pitched whistle could be another story. Did the idle seem high, or did it experience RPM surges while you drove it?
#4
Junior Member
Join Date: Oct 2014
Location: Lawrence, MA
Posts: 34
Likes: 0
Received 0 Likes
on
0 Posts
Year: 1999
Model: Cherokee
Engine: 4.0L I6 HO
A great way to seek out a vacuum leak under the hood is to get a can of ether and spray areas where vacuum plays a big role. If the engine suddenly surges, you've found the leak. You can also use water, but I've found this method less reliable. Id be looking at vacuum connections for cracks and looseness as well.
Another thing worth checking out may be if the air filter housing is completely sealed. I had a light whistle on mine when I picked it up, found that, and solved it just by closing it properly.
#5
Senior Member
Thread Starter
Join Date: Sep 2014
Location: Austintown, OH
Posts: 625
Likes: 0
Received 3 Likes
on
3 Posts
Year: 2000
Model: Cherokee
Engine: 4.0
yeah, its pretty noticeable and sounds close to the firewall. it goes away for a second when you give it gas but comes right back. I've done the ether thing also, but I've never heard one make that noise though.
#7
Seasoned Member
Join Date: Mar 2014
Location: Central Texas
Posts: 498
Likes: 0
Received 0 Likes
on
0 Posts
Year: 1996
Model: Cherokee
Engine: 4.0
I fixed a friend's bravada (blazer) once that had a vacuum leak in the HVAC controls. More or less what you described, it was a high-pitched hiss that would drop out at higher rpm.
Trending Topics
#8
Junior Member
Join Date: Oct 2014
Location: Lawrence, MA
Posts: 34
Likes: 0
Received 0 Likes
on
0 Posts
Year: 1999
Model: Cherokee
Engine: 4.0L I6 HO
Crash Course has a point there. There are a few vacuum lines tied into the HVAC system. if one of those hoses fell off, or there is a leak in the casing or lines, that could cause the same symptom
#10
Seasoned Member
Join Date: Mar 2014
Location: Central Texas
Posts: 498
Likes: 0
Received 0 Likes
on
0 Posts
Year: 1996
Model: Cherokee
Engine: 4.0
Also the actual valve that redirects the vacuum when you move the lever... Which was the issue with that Olds. The plastc clip holding the two halves of the valve together had broken. I haven't had to take apart an XJ HVAC control yet, but there's always that possibility as well.
#12
Senior Member
Join Date: Sep 2014
Location: Saginaw Mi area
Posts: 580
Likes: 0
Received 0 Likes
on
0 Posts
Year: 1994
Model: Cherokee
Engine: 4.0
Another thing that works to locate a vacuum leak is a propane torch.
Turning it ( un-lit of course !) on and passing it over suspected leak areas will usually make the idle speed pick up a bit, if there is a leak.......
Also, WD40 works too....
Turning it ( un-lit of course !) on and passing it over suspected leak areas will usually make the idle speed pick up a bit, if there is a leak.......
Also, WD40 works too....
Thread
Thread Starter
Forum
Replies
Last Post
Blackcherokee290
Stock XJ Cherokee Tech. All XJ Non-modified/stock questions go here
27
07-26-2022 07:52 PM
JeepsAreForSpeed
Stock XJ Cherokee Tech. All XJ Non-modified/stock questions go here
7
08-04-2020 05:14 AM
RunnerInPink
Stock XJ Cherokee Tech. All XJ Non-modified/stock questions go here
25
10-10-2017 10:34 AM
95cherokee89
Stock XJ Cherokee Tech. All XJ Non-modified/stock questions go here
59
10-16-2015 03:17 AM
Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)