Overheating with A/C

[menos]

Update: I'm pissed.
Tranny cooler did nothing. Trans temp was sitting about 120-150.

I got the cooler and the gauge from summit racing.


It's shooting up quick now. From completely cooled off to in the red in less than 5 minutes of driving. The weird thing is that no mater how hot it gets (its almost made it all the way to the right) the level of fluid in the overflow tank never changes.

So, It's not:
-the tranny overheating
-a clogged cat
-a bad radiator

It's got a new:
-radiator
-water pump
-thermostat (dealer and 180, same result)
-radiator cap
-tranny cooler

I'm gonna get an IR gun tomorrow at lunch and see where I sit. What should I shoot? The thermostat housing? What kind of temperature variation should I expect to see between the thermostat housing and the dash gauge?

 

[menos]

Well crap.... Gauge is accurate. I started puking fluid today. Gauge was pegged and IR gun read 255 at the thermostat housing.

At this point I'm thinking its something in the motor itself. What are some of the internal causes of overheating? Clogged passages? Bad headgasket? Cracked head? Any others?

 

[Ecomike]

Well crap.... Gauge is accurate. I started puking fluid today. Gauge was pegged and IR gun read 255 at the thermostat housing.

At this point I'm thinking its something in the motor itself. What are some of the internal causes of overheating? Clogged passages? Bad headgasket? Cracked head? Any others?

Check the temperature coming out of the radiator and returning to the engine just for grins.

I would take it to a radiator shop or mechanic that has a radiator cap adapter / hand pump for pressure testing the coolant system at the radiator to see if it is holding pressure next. If your loosing pressure look for the leak externally before assuming it is a head gasket.

I am told that the coolant can be tested for exhaust gases with a sniffer and or chemical test strip, and the exhaust pipe can be tested for coolant with a sniffer, but I have never used one.

It is possible that a biased sensor(s) (O2, MAP, CTS, or a combo of them) is tricking the engine into running too lean, but it is not very probable, since you say the engine is running fine, good power, etc.

Use your IR gauge to Look for an exhaust manifold leak heating up the block or intake manifold on the drivers side. I assume there is no oil the coolant, and no coolant in the oil yet?

 

[menos]

Just for grins I replaced the thermostat again. I've got a new dealership one in there now. It's doing MUCH better, but it still shows that it is running hot. The gauge is sitting at 225-230. I shot the thermostat housing with my IR gun and it is reading 200-205. Should there be that much variance between the gauge and the IR gun temp?

I shot the return hose and was getting about 180, but I don't know how accurate that reading is due to the rubber hose.

I went ahead and did a compression test and everything looked good there. 155-170. I haven't had a chance to do a leak down test yet. No coolant in the oil or oil in the coolant.

It was 103 here this afternoon. I went out and ragged on the truck and it never got into the red.

I've got a new gauge sender that will be here in the morning. I'm gonna kick myself it is just the gauge, but I'm not entirely convinced of that yet. We will see tomorrow though.

 

[igotanxj]

Did you ever make sure you got the air out of the system? It would make the difference between overheating and being normal.

 

[Blaine B.]

Since the radiator is out of the question, how are the water pump impellers? Really can't tell unless you take the water pump out. Unless you check for flow.

Secondly, how old is the thermostat?

Third, how old is the mechanical fan CLUTCH?

Fourth, how old is the coolant, and when is the last time the system was flushed?

 

[menos]

Water pump is new.
Thermostat is new.
Clutch is about 6months old but it overheats on the highway also so doesn't that kinda indicate is not an airflow issue?
Coolant is new, flushed last week.


New gauge sender is in. Same results. I'm gonna rent a pressure tester and test the system to see if I can find any leaks.

 

[Ecomike]

Since the radiator is out of the question, how are the water pump impellers? Really can't tell unless you take the water pump out. Unless you check for flow.

Secondly, how old is the thermostat?

Third, how old is the mechanical fan CLUTCH?

Fourth, how old is the coolant, and when is the last time the system was flushed?

The answer to all those questions is in the first thread!

 

[Ecomike]

Water pump is new.
Thermostat is new.
Clutch is about 6months old but it overheats on the highway also so doesn't that kinda indicate is not an airflow issue?
Coolant is new, flushed last week.


New gauge sender is in. Same results. I'm gonna rent a pressure tester and test the system to see if I can find any leaks.

Perhaps the dash gauge is wrong, may need calibration, or there may be a bad wiring connection between the dash gauge and sensor, or feed voltage to the sensor, or partial short.

I would be inclined to beleive the newer IR gauge, The thermostat housing and radiator outlet hoses sound OK, indicating 25 F drop across the radiator.

I have an idea! The engine / gauge temp sensor for the gauge is a resistor, check the FSM for the sensor resistance at say 205 and 230 F, use an ohm meter to see what the sensor resitance is really telling the dash gauge, then you will know if the dash gauge is off (or wiring to the gauge, ground wire problem???) or not. Be sure the sensor is electrically disconnected from the harness during ohm testing with the engine running.

Sounds like the Dealer thermostat dropped the temp a good 30 F! Very interesting indead!!!!!!

If the read block temperature is indeed 30 F higher than the thermostat you could have blockage in the head or block, or maybe trapped air acting like a vapor lock.

JUst for gins check the engine head / block ground to the battery. Should be under 1 ohm. The Temp sensor you just replaced is a wire item that uses the engine ground for continuity!!!!

 

[1familyxj]

Just for grins I replaced the thermostat again. I've got a new dealership one in there now. It's doing MUCH better, but it still shows that it is running hot. The gauge is sitting at 225-230. I shot the thermostat housing with my IR gun and it is reading 200-205. Should there be that much variance between the gauge and the IR gun temp?

I shot the return hose and was getting about 180, but I don't know how accurate that reading is due to the rubber hose.

I went ahead and did a compression test and everything looked good there. 155-170. I haven't had a chance to do a leak down test yet. No coolant in the oil or oil in the coolant.

It was 103 here this afternoon. I went out and ragged on the truck and it never got into the red.

I've got a new gauge sender that will be here in the morning. I'm gonna kick myself it is just the gauge, but I'm not entirely convinced of that yet. We will see tomorrow though.

At least ypurs isn't actually overheating anymore. I installed my t stat and T stat housing and it still seems to be getting hot on freeway in overdrive with a/c on. If I shift out of Over drive and turn A/C off it drops right down. I know the rheostat in my gauge is bad because at about 225 to 230 it jumps all the way up to about 250. When it cools down it jumps from 250 back down to 225 to 230. I don't know exactly how hot mine is running. I am going to get an IR gun and test it to check my temperatures.:dunno:

 

[menos]

Well, I put the new sender in but that didn't change what I was seeing on the gauge. I measured the resistance of the sender and came up with some numbers that are a little off from what I was expecting according to the FSM. I've got another 91 xj so I swapped the gauges. That didn't fix it either. So my best guess is that there is something wrong with the electrical between the sender and the gauge or there is something that is causing the temp to spike right near the sender.

 

[menos]

So I finally got around to looking into this a little bit more. I decided to see if there may be anything wrong with the #6 cylinder, so I disconnected the injector and spark plug on #6. The temperature on the gauge started acting normal. Once I reconnected everything, the temps started showing high again.

What are the options here? Cracked Head, Blown exhaust gasket, cracked exhaust header?

 

[1familyxj]

That sucks. Mine still gets hot after driving a long ways on the freeway but it got better after I installed my new fan clutch. If the temps are lower than 95 it doesn't give me too many problems. I would look real close at your spark plug for cylinder #6 and see if there is any evidence of a problem there. next you can try to find an exhaust gas analyzer and see if it picks up any exhaust gasses at the radiator cap with the cap off and the engine running.

 

[Ecomike]

Low flow from a partially plugged injector, running lean if your lucky?

Burned exhaust valve or head gasket,,, if your not so lucky.

Try swapping 2 injectors next!!!

 

[menos]

I'll try swapping injectors next. I've got another XJ I can borrow one from. If that doesn't take care if it I guess it's time to pull the head.

One weird thing though, I've got a definite rich exhaust smell, and I've got a black ring around the tail pipe. If I'm running lean in one cylinder, would the computer try and compensate and dump more fuel into the other cylinders?

 

[n1ywb]

Could be a big air bubble by #6 if you didn't burp properly. There are plenty of burping threads on here.

Leakdown test is required to check head and gasket.

Do a cooling system pressure test, you can borrow the tool from Autozone. I borrowed it and never returned it, I've had so many cooling problems with XJs :/ In my experience cooling system leaks are the most common problem. The cooling system is like a pressure cooker; by operating under pressure it increases the boiling point of the coolant. If it can't hold pressure, it will boil and overheat for damn near certain. Even if it just boils in a pocket, say by your #6 cyl, that will destroy the systems ability to cool.

TStats have a high DOA rate. I test mine in hot water with a thermometer before I install them now. I also run a failsafe tstat so that after the engine overheats it sticks OPEN instead of CLOSED like normal ones do.

You could run without the tstat for a while and see what happens. In such hot weather with the AC on you probably don't even need it to reach operating temp. Might make it easier to track down the real problem. Of course you should normally use a tstat because if the engine can't reach operating temp it won't go into closed loop mode and bad things happen.

Water wetter works great! Try it!

 

[menos]

-With how many times I've flushed and filled the system I'm doubting it's that.
-I've done a compression test, good numbers, but not a leakdown test yet.
-I keep meaning to do this.
-No crap. I've been through so many tstats I keep a couple in the truck just in case.
-Haven't tried it yet, but don't really like the idea of running without a tstat.
-It's got some in it.

Because of the way it is behaving now, I'm really leaning to something physically wrong with the motor somewhere around the #6 cylinder. I guess I feel better about being able to track it down, but I'm not looking forward to dropping the cash and time to pull the head.

Could be a big air bubble by #6 if you didn't burp properly. There are plenty of burping threads on here.

Leakdown test is required to check head and gasket.

Do a cooling system pressure test, you can borrow the tool from Autozone. I borrowed it and never returned it, I've had so many cooling problems with XJs :/ In my experience cooling system leaks are the most common problem. The cooling system is like a pressure cooker; by operating under pressure it increases the boiling point of the coolant. If it can't hold pressure, it will boil and overheat for damn near certain. Even if it just boils in a pocket, say by your #6 cyl, that will destroy the systems ability to cool.

TStats have a high DOA rate. I test mine in hot water with a thermometer before I install them now. I also run a failsafe tstat so that after the engine overheats it sticks OPEN instead of CLOSED like normal ones do.

You could run without the tstat for a while and see what happens. In such hot weather with the AC on you probably don't even need it to reach operating temp. Might make it easier to track down the real problem. Of course you should normally use a tstat because if the engine can't reach operating temp it won't go into closed loop mode and bad things happen.

Water wetter works great! Try it!

 

[Ecomike]

THe rich running and overheating only when #6 has fuel and spark, makes me suspect a lean #6 and rich feed on others. TRy swaping say the #3 with #6 injectors and get an IR temp gauge to see if the heat problem moves.