90k miles

[Speed_racer]

Bought my XJ 2 months ago, had 90k on it.... had to replace water pump, fuel pump, starter, alternator, radiator, thermo housing, and 160* thermo.....

Have also added new plugs, wires, cap, rotor...

What else should I do to get it running perfect? Im at 6" lift, 32's. and only get 10 MAYBE 11 MPG.. I know it doesnt have to be that low... what to do?!?

[martin]

Speed Racer you need to replace that 160F thermostat with a 195F thermostat. The way the engine control is set up the coolant temperature determines if the computer operated in "open" loop or "closed" loop mode.

It Open loop mode the computer provides a pre determined amount of fuel. It generally very rich to prevent lean burn and hopefully heat up the engine sooner. The oxygen sensor is not monitored.

In Closed loop operation the engine monitors the oxygen and adjusts the fuel to provide an optimal fuel/air ratio.

With you 160F thermostat you never get into closed loop operation. That could explain why you get such bad gas mileage.

It is 180F when the transition from closed loop to open loop occurs.

My recommendation is go to the dealer and buy a Mopar 195F thermostat. It comes with a nice gasket.

[Speed_racer]

Will do Martin, was definitely something I was hoping someone could help me on! I appreciate it!!!

Now, can I not use the 195 they sell at Autozone?

Also, with the 160, my j eep still gets up to 210-215 sometimes, is that a sign that with the 195 ill overheat a lot?

[AZ Jeff]

NORMAL operating temp for an XJ using OEM parts is about 200 degrees, give or take 10 degrees.

If you trying to make it run cooler, you are defeating the system the way it was DESIGNED to work!!

Do as others suggested: get a 195 thermostat. Be sure to get one that has a "bleed hole" near the outer perimeter. If it does not, one can create a hole by drilling a 1/16" dia hole at two locations on the perimeter, 180 degrees apart. Be sure to install the new thermostat with the bleed hole on the top .

[Backdraft]

On the low MPG are you sure the speedo gear has been replaced to compensate for the tires? Just a thought, but it can throw your readings off.

Mike

[martin]

Speed, you can use what every theromstat you want. First off think the thermostat keeps you engine from getting too hot or too cold. It a very simple device and if it is bad it can cause you to destroy the engine.

I paid between 8 and 10 bucks for a theromostat at my dealer but that was 3 years ago. The thermostat comes with a very nice gasket.

Also the guys on here have posted over the years that the Mopar 195F is the only thermostat with a vent hole to allow the air to pass when you are burping the engine.

For the few extra bucks I'd go to you local Jeep dealer and buy one. If you don't have a jeep dealer in town then go to any Chrysler/Plymouth/Dodge dealer and they will be able to get you the part. If not in stock then over night.

We did a Case study on Chrysler in my Management Information Systems Class. It showed how the dealers were hooked up by satellite and that ANY "Chrysler corp" dealer can look up and get parts for any division's vehicles.

I have not NO problems with my Mopar themostat. Remember the Mopar thermostat "has to work" because of the statutes of supplying spare parts for 7 or 10 years. The Federal Gov't would be all over Chrysler if their spare parts did not work. On the other hand, the aftermarket should work but there no Legal obligation to customers to make srue they work. Also 10+ years ago there was problems with PCV valves and Thermostats. Since then I have come to the conclusion there is added value to buy the OEM stuff at the dealer. I'll spend $5 more for a mopar thermostat to prevent overheating an engine which costs me thousands to replace.

[Speed_racer]

Good point Martin.

Can someone plz explain to me the diff between an open and a closed cooling system , which is better, and how do you achieve it?


Backdraft, i use dto get about 320 per tank, now i get 200, I doubt its off that much....

[Backdraft]

If that is the case the scratch the bad readings thought. My brain isnt working right now but I might have another idea later about it if you dont get it figured out first.

Mike

[Rob Mayercik]

Originally posted by Speed_racer
Good point Martin.

Can someone plz explain to me the diff between an open and a closed cooling system , which is better, and how do you achieve it?


If you have a pressure cap on the radiator, you have the open system. If the pressure cap is on a plastic reservoir, it's the closed system. IIRC, the open system came in around 92, and may have gone back out again in the last year or 3 of production. What model year is yours?

As far as which is better? I think the only downside to the closed system is that plastic bottle, which reportedly ages and cracks periodically. Of course, you don't have to live with it - Eagle pioneered the swap to a billet aluminum bottle (which takes a traditional-style radiator cap) made by Moroso. He (or someone else who has done the swap) can perhaps chime in and give details.

Rob

[Texas88XJ]

Speed, your sig says you have a 93 model. You should have the desireable "open" cooling system. My 88 is the undesireable "closed" system. The main difference is yours has a radiator cap and a coolant recovery bottle. Mine has no "radiator" cap and the cap on my plastic bottle acts as the radiator cap because the bottle is pressurized. This is bad because the plastic bottle and cap can fail easily due to the constant pressure. Someone correct me, but I think XJ's went to the open system in 91.

[xjwoody]

I made the switch to the 91+ open system on my 87. It runs really cool, now. A new radiator, heater control valve, recovery bottle, some heater hose and about 6 hours is all it took. My 87 rarely breaks 200. I don't think there are any long term issues with this mod. If anyone has an opinion, I'd love to hear it.