TuffMdr

I just did an overhaul of my cooling system to try and regualte my engine temps. I have a 2000 (167,000) with the original 0331 and just want to ensure it stays cool. Prior to the overhaul I would run 210 normal driving but get creep on hot days especially at stops. I had already replaced the mechanical fan with a mopar about 8 months ago. I would hit 221-222 and run the heat to drop it. I never run my AC as it really doesnt work. I did a prestone chemical flush followed by a full hose flush of the block and heater core. I replaced my waterpump with an AC delco pump and my radiator with a CSF 2 core, I replaced my thermostat housing and thermostat with a STANT and drilled a slightly larger than 1/16th hole at 12pm to help with burping. I cleaned everything well and replaced the radiator hoses and inlet tube...everything except the heater hoses and did not replace the temp sensor. I did wire brush the sensor to get some of the build up off. I have burped the system twice. Yesterday front end up on ramps, engine running, funnel full and squeezing the upper rad hose. Ran it in the driveway for 15 min and never topped much over 210 (OBDII reading on my phone). Today comming to work (not a particularly hot day here in VA) I ran 208-210 for most of the drive then stopped in a fast food line and crept to 221-224. It took a while to cool back down even once on the highway and with the e-fan on. Could my temp-sensor be bad? or is my burping process not right?

jordan96xj

You said you replaced the mechanical fan, do you mean you replaced just the fan? or the viscous fan clutch?


The symptoms you describe sound like the viscous fan clutch. Temps creeping up when stationary.


Is your electric fan coming on during any of this? Usually by 222f it should have responded by coming on (it varies a little from model year to year, but generally it is on by 222f).

TuffMdr

I replaced the clutch. e-fan is kicking on properly. Like I said it seem though to be taking a bit longer than I would expect to cool back down even after highway run, but it could be delay in my Bluetooth OBDII app. Also I would think with the flush and new components on a not so hot day that I wouldn't creep so fast. But I will check the fan again...run it till at temp then shut the engine off 2-3 rotations of the fan till stops - right?

PatHenry

If you got a lifetime warranty on the fan clutch, I'd just go ahead and replace it. The quality of many aftermarket ones are not so great.

Did you check the actual temperature at the t-stat housing with a temp gun? That will tell you if your temp sensor is bad or not. If it's not reading correctly, on a 97+ XJ, you definitely want to replace it with a quality replacement part since the computer does use the temp value - unlike 96 and earlier.

TuffMdr

So I just went out to get lunch. Popped my hood - engine cold... both rad hoses are flat. WTF? Pulled the cap and massaged them open..a few bubbles came up - I added some fluid. There was plenty in the overflow. Drove it for 20 min. It never went much above 210 - got out and the hoses seem fine

fb97xj1

The hoses collapse when theres vacuum in the system.

I pulled the following from Google.

"The most common cause for radiator hose collapse is a vacuum issue caused by a faulty radiator cap. Another common problem is clogging of the smaller radiator runoff hose, which leads to the coolant tank. As the engine cools, if fluid cannot return to the tank, this will also cause a vacuum."

Tbone289

Yep. check your hose to the overflow and see if you can blow through it..

TuffMdr

Will check for sure but I cleaned the reservoir and hose when I flushed the engine - radiator cap is a new STANT 1033.

EZEARL

Might want to try a cap w/o the lever. Read here of a few failures with them. Try a Stant 10231.

TuffMdr

I will put my old cap on when I get home just to rule it out. I will also make sure there is nothing in the bottom of the overflow or overflow hose blocking the return of fluid.

EZEARL

That'll work. Good luck.

TuffMdr

So I blew this out of my overflow tank tube. It is very thin walled tubing...almost like heat shrink but flimsy... no clue. It was definitely obstructing. Almost acted like a 1 way valve. I am going to assume it is the reason for the hose collapse (and will keep the stant lever cap on for now) but am not convinced it is the reason for the high temps .... unless somehow that causes air to get back in the system. Anyone think this could cause my issue. I'll have to test drive again.

PatHenry

How are you not convinced it's the reason for the high temps? The blocked hose creates a vacuum which constricts your U/L hoses and hence constricts coolant from flowing. You literally have seen this happen.

Replace the hose (you can buy it by the foot at your local parts retailer) and make sure you have a functional 13lb radiator cap on it and see if things don't improve.

TuffMdr

Makes sense. All my parts look up said 16psi... its a 2000 with a 2 core radiator... am i wrong and it shpuld be 13?

BlueRidgeMark

I don't know the correct pressure, but better too low than too high, until you are sure.