This thread has now been superceded by viewtopic.php?f=5&t=54207 . It is much more complete and detailed.
The purpose of this thread is to compile information that comes up often from new CRD owners and those considering a CRD purchase that have some questions. I will address as much as I can think of, but I'm sure others will be able to add more information to this thread.
The CRD is a great engine in a small 4x4 SUV. You will not find a better combination of torque, off-road-ability, and economy short of importing a diesel Land Rover Defender - and those don't have A/C. However, the platform application in the US and Canada left a little to be desired.
First is the combination of Exhaust Gas Recirculation (EGR) and Closed Crankcase Ventilation. (CCV) These are EPA-required (not sure of Canada's governing body) emissions components on all passenger vehicles sold for highway use in the United States. The EGR directs a percentage of exhaust gases into the intake to be combusted. Unfortunately, diesel exhaust produces soot, and that soot ends up in the intake of your engine. Ever busted a toner cartridge? Yeah, like that, but worse.
Here is a good pic of soot in an actual EGR valve (thx DZL_LOU and DarbyWalters):
Here is picture of an important sensor, called the Manifold Absolute Pressure (MAP) from the intake tract of a CRD, the way it SHOULD look (thx old navy and DarbyWalters):
Here is that same sensor coated in soot from the EGR (thx chispitude):
The CCV is another component that allows gases from the crankcase to escape the engine and go into the intake for combustion. In most situations, there would be no problem with this, vehicles have had these since the late 60's. However, the "puck" on the top of our engines that allows the gases out also allows engine oil out in a condensate, or mist, form. That oil collects in the intercooler hoses and degrades them over time, and, worst of all, combines with the soot from the EGR to produce a sludgey, tar-like substance that coats the intake tract, sapping performance and triggering Check Engine Lights. (CEL)
Here is picture of the same sensor above coated in oil from the CCV (thx 0311_DoC):
This combination of EGR soot and CCV oil is the root cause of probably 75% of owner maintenance/ repair issues with the Jeep Liberty CRD, and those issues can be solved with a few simple actions.
First things first, unplug the MAF sensor to disable the EGR and stop the flow of exhaust (read: soot) into the intake. (Link here: viewtopic.php?f=98&t=22631 ) It will cause a Check Engine Light, but it is a good temporary fix until you can make a decision on a GDE tune, other tune, or SEGR, which diminish or negate EGR recirculation. As stated, soot in the intake of a diesel is BAD.
Next, install an Elephant Hose (or Provent) to stop oil mist flowing into your turbo and intake tract. (Link here: viewtopic.php?f=98&t=22703 ) As stated above, mix that oil with soot from the exhaust, (EGR) and you get sludge in the intake. It builds up, restricting the flow of air and affecting the MAP sensor reading, which is next.
Clean the MAP sensor with chlorine-free brake parts cleaner. Link here: ( viewtopic.php?f=98&t=22630 ) Make sure you do not lose the small washer on the bolt.
So now, you've spent 30 minutes, and little to no money, and you will have a much more responsive and economical machine. Get out on the Interstate and run it hard to clear the cat of any soot buildup, and to enjoy the power. Now it's money time. . .
If you are a new owner, order a test kit from Blackstone or another oil analysis lab, drain the oil and catch a sample to send off to find out about any possible abnormal engine wear. Refill with a quality 5W-40 SYNTHETIC diesel-rated oil (such as Mobil 1 Turbodiesel Truck or Shell Rotella T) and replace the oil filter with a quality filter such as Wix or Purolator Pure One. (Unless you have solid records from the previous owner/ dealer that indicate this is not necessary) Replace the drain plug with a Fumoto valve, this will make oil changes infinitely easier and prevent you from damaging the threads on the cast aluminum oil pan. Link here: ( http://lubricationspecialist.com/front/ ... roductid=5 ) Greg with Lubrication Specialist is a LOST member.
After these simple things, the world is your oyster. Spend some time surfing LOST, and you will find a wealth of information about the various options for the GDE tune, SEGR, Provent, exhaust mods, lifts, etc. Most members have their mods in their signature line, if you have a question, PM them and 99/100 times you will get a positive, informative response. After about a month or so of regular visits and reading, you will become familiar with common issues and fixes discussed here on the board.
