First let me start off with a little background on my car. I just recently bought this car at auction for $4300. It was a DUI seizure and was a one owner car before me and the police. I have no information as far as previous repairs or maintenance. The car currently has 106k miles on it. that being said, here are my issues I'm having.

1- I have an air/vacuum sound coming from right under where the black air intake tube connects to the motor.

2- I can smell coolant in the engine compartment, but cannot find a leak anywhere. Smells more like its on the passenger side near the front.

3- There is a humming sound coming from the rear of the car when driving. The faster I go the louder it gets. It's not real loud, and does seem to go away or at least get quieter when going around big curves.

4- Every now and then when I come to a rolling stop there is a very very slight pause and a bit of jerk as soon I give it gas to take off. Almost like there is a viod in the driveline somewhere. If I come to a complete stop and then go it doesn't happen. Keep in mind this occurs about 40% of the time.

Any help would be appreciated.

 

Hi,

Wow, what a great deal. I just bought an '04 XJR and paid much more than that.

I'm new to Jags, but I've been doing a lot of reading about this car and might have a little info.

#1 - No help here, sorry.

#2 - Your coolant issue gives me two ideas. One, the coolant reservoir tank seems notorious for the plastic nipple breaking off or cracking. This is the part that the rubber hoses attach to. I think to fix this, you'd have to replace the coolant tank. However, someone on here had a post about epoxying a brass nipple into their tank. The other possibility is the valley hose under the supercharger. Search this site and you will find tons on info on that issue. The valley hose is a big job and expensive to replace unless you don't mind doing the work yourself.

#3 - The humming might be the differential. I'm just guessing here, but I'd check the oil level in the diff. The fill/drain plug has a magnet in it and is supposed to collect metal shavings present in the oil. If the oil is really dirty and you have a mushroom of sludge stuck to the fill plug, change the diff oil.

#4 - sounds like a transmission issue. I'd start with a transmission service. Change the fluid and install a new drain pan. There is much argument about it here, but I would only use the ZF LifeGuard 6 transmission fluid that this car was designed to use. The pan has the filter built into it and has to be changed to change the filter. You can get a kit to do this yourself here: Oil change kit for 6HP26/28/32 I haven't done mine yet, but will do in the future. For now, mine is driving beautifully. Again this is a pricey job to have a mechanic do but if you don't mind doing things yourself, its not to bad. Search this site, there are some great posts on how to do this job.

Best of luck. At the price you paid, you have a lot of room to repair costs, and you still got a great deal.

 

Get an OBD tool with live data - fast. Check fuel trims. If you have an air leak, fix it before the cats burn out.

Great deal, though.

Humming is next. Might be a bad wheel bearing.

 

mrwhite - I did read about the coolant tank issue but i see no signs of it leaking. I guess it can't hurt to replace it anyway just to rule it out. After reading about the valley hose you mentioned I sure do not want to do that if I don't have to. I will also check the differential fluid later today. And as far as the transmission goes, I thought you were not suppose to change the fluid in these cars. I did read were some people are saying to have the car reflashed to fix tranny issues but I don't know if my problem falls into that category.

 

jagv8 - I will pick up an obd2 with live data today if I can find one reasonably priced in town. If not I will order one online.

I tried finding the air leak but had no luck. It is definitely coming from right in the front under where the plastic air intake tube connects. Is there anything right there that you know of that would be causing that? There's a lot of hoses under there and I just cannot pinpoint the leak.

As far as bearings go, are they hard to do on these cars?

 

1. Agree with JagV8 on this. Most auto parts stores have OBD coders that they will connect to your car and provide you a readout. They sell the parts so it's in their best interest to do this and they do it at no charge. If they don't, buy your own. This should be priority 1.

2. The replacement overflow reservoirs are about $190 dollars and are a weak point but not the only one. Don't throw money at the problem. Diagnose it. Get a pressure test on it.
Jags have a rats nest of hoses right in front of the radiator and that's just the start. Some leaks can be as small as a pinhole. Again, auto parts stores usually rent a coolant pressure tester. This is a must. Chances are as good as 50/50 that the coolant hasn't been changed or the hoses during the life of the car. As these cars run on dexcool, they should be flushed and back-flushed every 5 years minimum. While your pressure testing for leaks, plan to replace any soft hoses. The Radiator, Engine, Super Charger and Heater Core are all flushed separately. This is priority 2 in my opinion.

3. As Mr White suggests, check the differential fluid and plan to change it with the mileage you have on the car. Also, rear bearings are suspect on these cars. I believe they are sealed and require replacement of the hub.

4. Transmission is not sealed for life, despite the original claims from the manufacturer. Pan, filter and fluid should be changed @ 50,000 ( or I sometimes see 60,000). Either way, you are due. This may resolve your acceleration problem or you may have to have the TCM reflashed. 50/50.

Also from Partick the Cat in another thread:
Brake fluid (unless you know for sure it was recently changed).
Engine oil & filter (if you aren't sure of the service history).
Fuel filter (ditto)
Spark Plugs (ditto)
Air filter & cabin filter (ditto)
Power steering fluid.

Download the service manual for free in the how to sticky of this forum.

Best of luck.

 

Here is a link to a video I made of the air sound I'm getting. You hear it more in the front. And the mic on my phone is to the right in the video.

 

With live data and a leak the trims will show it. Then spray TINY amounts of something such as propane near each joint in turn while watching STFTs and they'll go mad when you hit the right place.

Will find most but not all leaks (you can't get at some joints; some leaks only happen when driving).

 

#3 - I had a similar issue. Fixed when I replaced the lower control arms because the bushings were shot, which caused the rear wheels to angle inward at the top, putting a lot of undue stress on the CV joints. If that's the issue, the S-Type lower control arms are the same as the XJ8 and less expensive. It made a world of difference in ride, noise, and handling.

#4 - Unfortunately this is a "feature" of the 2004 XJ8. It doesn’t seem to drop down to the right gear in a rolling stop unless you come to a complete stop for a count of 2 or 3. Very annoying. I have never found a real solution to this problem.

But, it may be reduced somewhat by cleaning the throttle body with the appropriate throttle body cleaner and a soft toothbrush where the butterfly valve closes and meets the orifice, especially around the horizontal shaft. Basically it sticks. Since it is throttle by wire you can’t feel the stickiness with your foot like you can with a throttle cable. But you can feel it by hand, before & after. Cheap, easy, and you will notice a difference. But it won’t eliminate the transmission part of the jerkiness.

 

I appreciate all the advice. I'm working on getting a lot of the things your telling me checked out. Didn't want you to think im ignoring any of you. I will update as soon I get some results. It will most likely be over the weekend. Free time is hard to come by during the week for me.

 

OBD check is first thing to confirm leak. Vacuum leak could be tiny o rings on the tubes that connect to the air intake. also check to see that the air intake plenum is properly attached to the vehicle and the connections are clean. The clamps could be misaligned or simply not tight enough. There also could be a crack in the plastic plenum tubing. Lots of little bends and that could be broken.
The jerking while shifting sounds like transmission, the refill is the best shot, but a new torque converter may be required. That could drive it for awhile, but its a costly part to replace, due to labor.
RyeJag

 

My tuppence worth:

1. OBD must be quite special, not a cheapo one that can only read the engine codes. It needs to be one that can read all of the various modules codes that the JAg throws out. There are threads here that identify good workable ones.

2. Rear Diff whine, I have a similar noise that is caused by a small leak between the prop shaft and the Diff. I have had it looked at and been told to just top it up with oil every couple of moths and it should be ok. That was a year ago and it has been ok.

3. Check the coolant level on a daily basis to see if you have any leaks by removing the coolant cap and looking at the fill plastic mounds inside. The coolant level should sit in line with the upper plastic level. You will see what I mean when you look in there.

4. Vacuum leak, that just a hope and a prayer search I am afraid.

5. Flashing the TCM may help. My gearbox does exactly the same and I have had it flashed and oil/pan and sleeve changed. Mines a lost cause for sure.

6. Download JTIS, EPM and start getting your hands dirty.

7.You haven't said anything about your drivers side heater only blowing out cold air yet....

 

Priceless