steven72192

I just bought a 2001 xj Classic with 120k one owner and I'm having a few problems. First my hvac controls do not switch anything they only blow out the defroster, I had this issue on my other xj and it was the connection from the vacuum ball in the fender what else could it be? Another issue is my check gauges light comes on and goes off when I'm sitting still or extended idle I just have it a fresh oil change so I know it's not that, once again same problem on my previous xj and it was the oil pressure sensor is there a way to test it before I just buy one? Thanks for the help in advance

toasterknight

The AC issue is a vacuum leak.

steven72192

Where do you think it could be leaking from

jtm01xj

You are gonna have to go threw every vacuum line to find the leak...

extrashaky

You could try putting some smoke through the vacuum lines to find your leak.

Regarding the check gauges light, which one is reading outside of normal? The gauge light comes on when the temp is high, the oil pressure is low or the voltage has gone wrong.

CCKen

Here's some pics of the vacuum system in the engine bay. Some pics are of older model XJ's.


Click the pic to make it larger.


https://www.cherokeeforum.com/g/album/3212409

steven72192

Oil pressure gauge drops

extrashaky

Just because you have fresh oil in the engine does not mean you don't have low oil pressure. It's not the oil that creates oil pressure. The oil pump moves oil through the engine. When the oil encounters back pressure at the cam bearings, pressure is created. If the pump is not pushing forward enough, or the bearings are not pushing back enough, you won't have oil pressure, and your engine will not be lubricated properly. Obstructions elsewhere in the system can cause problems also.

However, before you go worrying about that, you should verify that you actually have low pressure and are not getting a false reading at the gauge. You'll need to pick up a mechanical oil pressure gauge. You can get a pretty nice one at Harbor Freight for $25 (less with one of their 20% off coupons). You simply unscrew the oil pressure sender and plug in the mechanical gauge in its place, then read it. You should read it when the engine is hot.

If the oil pressure reads normal on the mechanical gauge, you probably have a bad oil pressure sender. The oil pressure senders on these trucks frequently go out, and they are typically made so that they fail in the low direction to freak you out so you'll get it fixed. Replace it with a genuine Mopar sender from the dealer. Yes, it will cost more than an aftermarket sender from O'Reilladvanceautozone, but it will be much more reliable.

If the manual gauge confirms that you have low oil pressure, you have bigger problems. But don't assume either way until you have verified your pressure with a mechanical gauge.

steven72192

Thank you very much I will grab one of those gauges from harbor freight and give it a try

madmanmarty

Anyone ever put a mechanical gauge in the engine bay?