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Running hot

Talyn

Talyn

NAXJA Forum User
Location
Radford, Communistwealth of Virginia
Tried this over in mod tech and didn't get much luck. Figured I could try here.

My 2000 XJ is running a bit hot now that the weather is getting warmer. Above 210 with a 180* high flow t-stat. Does it in traffic and on the highway, but more so in traffic. Prior to my head swap it was running fine.. around 210 with a 195* t-stat. When the weather was cooler it stayed right around 180*. Coolant level is good and green. Also, this is with out A/C running. When I did the head swap(about 8000 miles ago) I also replaced stock parts with these parts:

-Flowkooler water pump (a bit disapointed with this, just like my orginal pump, but had an aluminum plate riveted to the impeller)
-High flow t-stat housing
-180* high flow Mr. Gasket t-stat from Hesco
-radiator hoses (lower one does have a spring in it)
-Coolant was changed with the head, flushed before and after head was installed

I flushed the system before and after the head swap. Coolant is nice and green with no loss. Air flow to the rad isn't blocked. Runs hot on the highway and hotter in traffic.

Possibly blocked rad? But why did it just start up?

T-stat possibly not as high flow as it should be? It does open as I saw in cooler weather with the engine staying at 180*. Maybe it isn't opening 100%?

Flowkooler doesn't flow as well as stock? Haven't heard any negatives about this though.

What about a partially blocked cat? It doesn't rattle and the exhaust doesn't smell like eggs.
Any ideas?

-Chris
 
I know it sounds counterintuitive. However, it can make a difference. Besides, on cooler days, it keeps you from running to cool.
Two things I did not see mentioned. First, did you get your radiator rotted out? Second, check the fan clutch. Geneally, overheating at idle points to the fan clutch.
I was plesed with the FlowKooler. ANother item I saw suggested and have tried was using some shims to raise the back end of the hood about 1/2 inch.
BSD
 
Talyn said:
Tried this over in mod tech and didn't get much luck. Figured I could try here.

My 2000 XJ is running a bit hot now that the weather is getting warmer. Above 210 with a 180* high flow t-stat. Does it in traffic and on the highway, but more so in traffic. Prior to my head swap it was running fine.. around 210 with a 195* t-stat. When the weather was cooler it stayed right around 180*. Coolant level is good and green. Also, this is with out A/C running. When I did the head swap(about 8000 miles ago) I also replaced stock parts with these parts:

-Flowkooler water pump (a bit disapointed with this, just like my orginal pump, but had an aluminum plate riveted to the impeller)
-High flow t-stat housing
-180* high flow Mr. Gasket t-stat from Hesco
-radiator hoses (lower one does have a spring in it)
-Coolant was changed with the head, flushed before and after head was installed

I flushed the system before and after the head swap. Coolant is nice and green with no loss. Air flow to the rad isn't blocked. Runs hot on the highway and hotter in traffic.

Possibly blocked rad? But why did it just start up?

T-stat possibly not as high flow as it should be? It does open as I saw in cooler weather with the engine staying at 180*. Maybe it isn't opening 100%?

Flowkooler doesn't flow as well as stock? Haven't heard any negatives about this though.

What about a partially blocked cat? It doesn't rattle and the exhaust doesn't smell like eggs.
Any ideas?

-Chris
Click to expand...

I think the problem could be one or more of the following (in order of likelihood):

1. Pocket of air trapped in cooling system after head swap.
2. Engine running lean. Check the colour of the plug deposits.
3. Bad fan clutch. Spin it by hand with the engine off when it's hot. There should be some resistance. If it freewheels, the clutch is bad.
4. Partially clogged radiator core.
 
Its nto the fan clutch because it runs at highway speeds. Besides it does have resistance and engages at the correct temp. At highway speeds tehe engine runs at 14.7 cruising, which is right where it should be.

How can air be trapper. Its been abuot 8000 miles and several months since the head was installed, wouldn't it have burped itself by now?

I'm leaning toward the radiator becaus eit over heats on the highway and in traffic.
 
Talyn said:
Its nto the fan clutch because it runs at highway speeds. Besides it does have resistance and engages at the correct temp. At highway speeds tehe engine runs at 14.7 cruising, which is right where it should be.

How can air be trapper. Its been abuot 8000 miles and several months since the head was installed, wouldn't it have burped itself by now?

I'm leaning toward the radiator becaus eit over heats on the highway and in traffic.
Click to expand...

It looks like you've ruled out the first three on my list so that does leave no.4, the radiator.
 
Dr. Dyno said:
It looks like you've ruled out the first three on my list so that does leave no.4, the radiator.
Click to expand...

Do you think it is possible to still have air trapped in the system?
 
It's not impossible. Park on a steep hill facing upwards and let the engine idle for a while with the heater/AC/defrost running (one of the three). Hopefully that'll burp any remaining air out of the system.
At least you live in PA where there ARE hills. In Kansas, that would be a bit more of a challenge. :D
 
Dr. Dyno said:
It's not impossible. Park on a steep hill facing upwards and let the engine idle for a while with the heater/AC/defrost running (one of the three). Hopefully that'll burp any remaining air out of the system.
At least you live in PA where there ARE hills. In Kansas, that would be a bit more of a challenge. :D
Click to expand...

I'll give that a try. Wouldn't it be grand if that was the solution
 
Talyn said:
how is it going to stop it from running hot? Its a high flow t-stat that is already open fully, how is putting in the 195 one going to do anything?
Click to expand...


The t-stat is supposed to open and close. If the 180 is open all the time then the flow of coolent through the radiator might be too fast. If the coolent don't slow down in the rad once in awhile it won't cool as well.
 
So far no mention of the electric fan - I assume it has one - and sudden temp rises may indicate the coolant temp sender, relay, or fan motor may not be working.

You can jumper the relay plug to power the fan and check it. Per Eric Giordano, "Coolant temp sensor : ... To test, use a high impedance volt-ohmmeter. Resistance should be less than 1000 ohms with a WARM engine (examples = 212* would be about 185 ohms, 160* would be about 450 ohms, 100* (not warm enough) would be 1,600 ohms).

A 180 degree thermostat may not trigger the coolant temp sensor, as figures I have read elsewhere indicate it needs 197 degrees to kick the relay.

Your values may be different in the 2000 but it works similar. If air conditioned, there may be diodes in the wiring from the A/C and temp sensor to prevent voltage backfeed and loss of sufficient power to activate the relay. Diodes can break down (just like in alternators,) and these may need checking.

I've been chasing this one down in my '90.
 
I thought of that, and it does make sense... but dismissed it as several people run this combo. I was running a high flow t-stat prior to this, and the FlowKooler water pump is similar to my orginal 2000 with the exception of a aluminum plate added to the back of the impeller unit. I'll try replacing t-stat with a non high-flow unit and see what happens. I'm going to laugh my ass off if it is flowing too much.
 
Last edited:
TiRod said:
So far no mention of the electric fan - I assume it has one - and sudden temp rises may indicate the coolant temp sender, relay, or fan motor may not be working.

You can jumper the relay plug to power the fan and check it. Per Eric Giordano, "Coolant temp sensor : ... To test, use a high impedance volt-ohmmeter. Resistance should be less than 1000 ohms with a WARM engine (examples = 212* would be about 185 ohms, 160* would be about 450 ohms, 100* (not warm enough) would be 1,600 ohms).

A 180 degree thermostat may not trigger the coolant temp sensor, as figures I have read elsewhere indicate it needs 197 degrees to kick the relay.

Your values may be different in the 2000 but it works similar. If air conditioned, there may be diodes in the wiring from the A/C and temp sensor to prevent voltage backfeed and loss of sufficient power to activate the relay. Diodes can break down (just like in alternators,) and these may need checking.

I've been chasing this one down in my '90.
Click to expand...

The e-fan does kick on. If it is rising over 210, the coolant temp sensor woul be triggered. There is only one temps ensor on my 2000 that feeds the computer, which in turn controls the gauge and the fan. But still, no fan is going to matter when yuo are doing 70 down the highway and it is still running hot.
 
Talyn said:
My 2000 XJ is running a bit hot now that the weather is getting warmer. Above 210 with a 180* high flow t-stat. Does it in traffic and on the highway, but more so in traffic. Prior to my head swap it was running fine.. around 210 with a 195* t-stat.
Click to expand...

Sounds normal to me. My 2000 has run temps similar to that from day one. In traffic, it'll work it's way toward 220, but the electric fan pulls it back down to about 210.

The different thermostat will govern the LOW END of your operating temperature range... (aka, a 195 t-stat will keep it from going BELOW 195 once warmed up), but has essentially zero effect on the high end of the range. That's what thermostats are for: to keep the engine from getting too COLD.

Remember... XJ's run hot. Always have!

Den
 
My 94 XJ over the past few yrs has had every cooling component replaced on it and for the most part it runs 210 or slightly below but in long traffic or in a crowded drive thru the temp will creap to 220 and the efan wil bring it back down...If this is whats happening then its normal i beleive also.

pete
 
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