96 4.0L running at 180F after radiator replacement...want it higher.

Hey everyone,

My stock radiator finally broke at the upper plastic hose connection. Prior to breaking, it was running 210F pretty much no issues. It jumped up a bit in traffic, but never got to any worries of overheating.

I just replaced the radiator with a Duralast unit (likely Spectra). I did not change anything else other than fully flushing the system again (I did that about 1.5 years ago as well). Using Prestone 50/50 premix.

Fan clutch is loose (with a little friction) when cold. Thermostat was closed when I checked it during the flush (Gates 195F, replaced 1.5 years ago), electric fan only turns on when A/C compressor is on. Water pump is a new Mopar unit also replaced 1.5 years ago.

At idle with HVAC off or A/C blasting...it does not get above ~184F measuring with IR thermometer on the thermostat housing. (I am in 20F weather right now, but that has never changed my operating temps before) Gauge in the dash matches this. Opening up the heater bring the temp down further (heater valve is bypassed).

Any other thoughts? It's clear my gas mileage is suffering quite heavily after watching it for half a tank.

Thanks!

Oh...and if you see my other posts, I did change my gearing to 4.56. I am on 31s. I have only been in city traffic since all of these changes. Gas mileage should not suffer from the gear change there, but anticipating it at higher speeds.

I'm more worried about operating temps and engine safety than gas mileage...keep that in mind.

Mine runs at around 180 also with new everything. Has for years... only gets to 210 after about 30 minutes in the woods... this is with a 195 Stat as well.... over 200k of dd duty with this same "problem"

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Thermostats don't seem to last as long as they used to. I am on #3 in 5 years. One self dissembled and was just loose bits when I took it out.

A lot of people run the "fail safe" thermostats. These work by permanently going wide open if they ever "overheat". Because we tend to run slow and lug the engines, it is not uncommon for the engine to "overheat". All of this can happen without losing any coolant out the 16 lb. radiator cap, but then you end up with a permanently open thermostat, not a good idea.

gearwhine said:

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Any other thoughts? It's clear my gas mileage is suffering quite heavily after watching it for half a tank.

Thanks!

Click to expand...

I agree that it couldn't hurt to try a new tstat. If that doesn't get it back to where you want, then do like the truckers do in the winter - partially cover your grill with some cloth or plastic to limit airflow through the radiator.

Thanks everyone. Glad to know 180* isn't necessarily damaging, but I would still like it to operate at least at the minimum my thermostat is set at. I am basically a stock set-up, and don't see why it should be operating any cooler.

Just ordered a new SuperStat 195* thermostat (no one local carries these??). I'll test it with the current Gates one in a pot of water and report back. If they're both on point, then I guess making a radiator cover will be the plan.

I've always ran a gates stat... probably 3 or 4 over the years. It's always ran cold

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OK...this has become interesting. I'm completely baffled.......

Drove the XJ around all morning with no issues other than the temp and mpg thing (mpg confirmed to be reduced by half...I got 60 miles for half a tank, no fuel leaks anywhere). I later removed and tested both thermostats, old and new....both perfect. I installed the new stants just because, refilled as much coolant as possible to begin burping it as I've always done and.....

No start. Cranks all day long. Only code that popped up is P0118 (high voltage coolant temp sensor).

-Tested resistance of the sensor...working correctly. Bought a new one to check; they both read similarly

-Pulled a plug...it has clearly been running very rich....which might help explain my fuel consumption.

-Fuel pressure is great. Can empty the rail, turn ignition on, and it fills right back up with solid pressure.

-All fuses under hood are good.

Two things I think (plus a special one) are possible here.

1) Wiring harness connecting to sensor is bad. Prior to my ownership, that female plug was replaced. Looks well done with pin connectors covered in waterproof heat shrink. Something else could be bad within the harness further upstream though.

2) I didn't disconnect the battery, so maybe something shorted out when coolant spilled out. All connections I checked (plus distributor) were dry though

3+) Something else just happened to go bad at the same damn time....


I will be getting help tomorrow to see if I am getting a spark. In the meantime...any other thoughts on where to go?

Thanks

Definitely do an ECU reset by unplugging the battery. I've had some weird engine behavior when the ECU sees a temporary low voltage (from attempting to start my XJ with a very low battery). I had to unplug the battery (which was then fully charged) before the weird behavior went away.

60 miles on half a tank is not due entirely to the engine temperature. I've been running a 180F t-stat for more than a year, and I never have had mileage anywhere near that low. About the worst I see is 100 miles to the half full when doing lots of short drives (less than 10 minutes). Highway driving nets 130 miles to a half tank.

I would put a fuel pressure gauge on it. Just because you are able to move some fuel does not equate to having pressure.

You should have 49psi.

Note that '96 is a one-off year when it comes to its fuel system. Your regulator is in the tank. No return line. However, your regulator is essentially the same as the prior years, it just has no vacuum line connected to it.

Confirm your fuel pressure before you move on. It is possible you have been running with low fuel pressure and thus poor atomization. It is conceivable the computer has tried to compensate and pushed things rich, hence poor fuel economy.

I expect you can "rent" a fuel pressure gauge for free.

Get real fuel pressure numbers before you conclude your FP is fine.

ECU reset in progress. I did just do a reset during the radiator install, by the way.

I have a spare fuel pump lying around, but no regulator, as I was confused by the whole 96 system. If the regulator is bad, do I just buy any earlier one, and leave that top hose connection open? Do I need to cap it?

Read through this: https://www.naxja.org/forum/showthread.php?t=1107991

Hopefully the pictures show for you. They don't show for me thanks to some glorious interface between the website and my browser.

You will note that some of the options for a FP regulator do not seem to have the desired results. The Crown unit actually works (remarkable exception for that particular brand).

And yes, in answer to your question, you do just install an ealier H.O. FP regulator and leave the vacuum input open to atmosphere. But you need to check FP to start with. Don't operate with an assumption either direction.

fuel is 49 psi on the dot with engine off with a slow leak down if left alone.. that could be the testing unit though. between 35-40 psi while cranking.

So... now that we're on fuel related stuff. I installed an inline check valve near the fuel tank...was having problems restarting on an uphill. I replaced all hoses and fuel filter at that time. just now realizing how long my jeep was down during the regear and radiator deal... this is all newly installed and pretty much still in test period.

I can't stte what the pressure is at idle at this point.

NO!!

Do not install a check valve on that fuel line.

Research that topic, particularly the installation of check valves on fuel systems with no return line.

That is a big no-no. There is no place for excess fuel pressure to bleed off.

Yikes... I tend to do a lot of research before doing any work on my stuff, but obviously missed the boat on that subject. I'll get a new hose and get rid of it immediately...I'll inspect everything thoroughly.

This is why I try to be complete with my posts.... Thank you!

Anak said:

NO!!
Do not install a check valve on that fuel line.
Research that topic, particularly the installation of check valves on fuel systems with no return line.
That is a big no-no. There is no place for excess fuel pressure to bleed off.

Click to expand...

I'm not sure what exactly your saying The late models use a check valve!

Anak said:

NO!!

Do not install a check valve on that fuel line.

Research that topic, particularly the installation of check valves on fuel systems with no return line.

That is a big no-no. There is no place for excess fuel pressure to bleed off.

Click to expand...

This is a pretty fascinating issue. I would have guessed that a check valve between the pump and injectors would be a non-issue while the vehicle is running and that the real issue would be potential pressure build-up after the engine is turned off and the fuel heats up due to the engine compartment.
While the engine is running (and fuel is flowing), there should be no means for excess pressure to build due to a check valve.

However, there seem to be a least one report excess pressure build-up while an XJ was running. The best I can estimate is that the pressure waves produced in the fuel system by the injectors opening and closing may be playing a role here, although I still can't see how.

RCP Phx said:

I'm not sure what exactly your saying The late models use a check valve!

Click to expand...

So does the '96, but it is inside the tank, as I expect it is for the late models.

You can bleed off pressure inside the tank without a problem. Bleed off pressure outside the tank and bad things happen.

I still don't see your point, the fuel pressure regulator acts to do the same thing on earlier models?