Cane

it's ordered, but it got me thinking... is it possible I have a pretty significant air bubble in the system, since my upper radiator hose feels empty at operating temp, and therefore the coolant temp sensor does not pick up the right heat? because after all, it needs coolant in order to read the temperature right?

today it stayed under 210 the whole way except in light traffic where the temperature started creeping up, but this time the aux fan did start!! which is why I'm wondering if air bubbles could cause this

salad

Air bubbles will screw with the thermostat, the ECT will conduct from the thermostat housing.

Cane

how will they screw with it exactly? possibly by making it not open? I don't grasp the whole cooling system, so pardon my ignorance.

how can I bleed the system correctly and get coolant to flow through the upper hose? before replacing things I need to make sure i don't have air pockets

since the hose itself gets a little hot, I'm guessing there is some flow, but even after a 20-25 min drive, i can't feel much pressure. videos I've seen show people pressing the hose and saying you should feel the flow through the hose.

salad

Yes, the air will collect at the thermostat and create an insulative pocket in front of it. Inside the thermostat, inside the spring, is a wax pellet. When the wax is heated, it expands and forces the valve open. This assembly is mounted in the middle, suspended by some little metal fins on either side. It takes a long time for that hot air and conduction of heat through the structure to make that pellet open, compared to when hot water is pressed up against it directly.

There are all kinds of tricks but the fool-proof method is to use an OE-type thermostat. The Mopar unit includes a tiny little "jiggle valve" which allows a small amount of whatever - in this case, air - to just slip by. No BS involved. There's an aftermarket version like this too, I can't remember if it's Motorad or Stant. Marked as a "high-flow". Once air is out of there it'll just slip out the rad cap into the pressure tank as the thing's driven.

I'm not in the habit of grabbing hot radiator hoses lol. Only hard hose I've felt is my truck's with a blown head gasket.

Cane

alright worst case scenario I'll have to flush some coolant again and remove the t-stat housing and replace it just in case. thanks for the explanation, I'll probably visit the shop that did the job and ask them if they can tell me what is the part they used and also what they think of my situation.

89XJDan

I've got a 2000 4.0L auto that needs a fuel pump, oreillys brings up two very different pumps at very different prices. Looks like they've got different connects and flow rates. Aside from pulling the pump, is there any way for me to figure out which one I need?

salad

05012953AB is the original fuel pump assembly for a 2000 XJ with 4.0L. Looks like it was superseded by 05012953AC, so whatever cross-references to those.

(You can do a parts lookup against the catalog at rockauto.com)

89XJDan

Thanks! I appreciate that. Everyone keeps telling me fuel pump but I'm not too sure... it takes a few key cycles to start, but pressure at the fuel rail seems to be strong. Is there any chance it's the the ignition switch? Or just needs some seafoam run through it?

XJwonders

check to see if fuel pressure stay the same 15-30 minutes after turning the engine off.

89XJDan

I had just ran out to check it after it sitting at work for about 3 hours, it was strong so I turned the key and no start, checked the pressure again and it was strong again. It starts after a few cycles, sometimes two, sometimes five, makes no difference if I pump the gas pedal or not.

XJwonders

what was the fuel pressure?

89XJDan

As strong as I've seen it on any other vehicle I've pressed the valve on. Sounds more like it's the starter or relay for the starter.

XJwonders

I would rather to verify with a gauge. Streaming fuel from the Schrader valve can be misleading sometimes


Does the lights dim when you start?

89XJDan

Lights on the dash all shut off except for the brake light, it doesn't turn over, there's no clicking noise, just dead.

salad

Poor Man's Prime deals with a failed check valve in the pump module. Fuel pressure at the rail should be 49 PSI almost immediately after turning the key, and hold it after shutoff for at least half an hour.

...now I'm confused. Your starter doesn't crank???