LX 450 Overheating. Help! (1 Viewer)

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undefinedMy 97 LX 450 (44,000 miles) is having an overheating/no air conditioning problem. After about 10 minutes of driving, the AC goes warm and the temp guage goes to 3/4. So far the Toyota dealer has recharged the air, changed the thermostat, pressure checked the cooling system, compression tested the motor, and checked the fan clutch. Everything checks out OK but the problem is still occurring. The 450 does not overheatr while idling, only when moving. Any thoughts, suggestions?

Any help would be greatly appreciated.

Matt
 
mclaren said:
undefinedMy 97 LX 450 (44,000 miles) is having an overheating/no air conditioning problem. After about 10 minutes of driving, the AC goes warm and the temp guage goes to 3/4. So far the Toyota dealer has recharged the air, changed the thermostat, pressure checked the cooling system, compression tested the motor, and checked the fan clutch. Everything checks out OK but the problem is still occurring. The 450 does not overheatr while idling, only when moving. Any thoughts, suggestions?

Any help would be greatly appreciated.

Matt

Head gasket.
 
Low miles for that trouble.

Most common causes:

Fan clutch
Sluged up radiator
Blown head gasket


The reason the A/C doesn't work is because the motor is getting hot enough to make the compressor cut out (226-228 F)
 
Do the Robbie test:


Open the hood and start the engine. pop the overflow bottle cap off so you can see down inside but keep the end of the draw tube submerged. Have an assistant run the engine up to 3,000 rpm and hold it there. Watch for bubbles in the jar. Bubbles = blown head gasket.
 
Correct me if I'm wrong here but wouldn't the engine compression test reveal the HG issue ?
(bubbles = leakage)

Do you see the coolant hoses deformed once overheated ? If yes ==> pressure cap.
I'd suggest the other Robbie test: grabbing the fan clutch (search the archive for procedures)
Also, look for possible blockage on the radiator and ac condensor fins.

Frank.
 
A compression test wil not find all bad head gaskets. Often the pressure does not get high enough for the trouble to show up. A cylinder leak-down test is more reliable for that.
 
LX 450 Overheating

The toyota dealer was thinking headgasket but has apparently ruled that out based on the pressurizing of the cooling system test and the compression test. The mechanic is seems stumped. Would the radiator cap or ac drain lines really cause this kind of overheating? Toyota suggested that the AC compressor could be seizing and causing the motor to overheat. Sounds unlikely to me.
 
As noted above, the AC cutout is likely a red herring. It is supposed to cut out when you overheat.

If your temp gauge is going to 3/4 you are seriously heating up this truck. Do an archive search here on "temp gauge" and "overheating" and you will find posts explaining the flat spot sensitiity of the 80 series temp gauge. Basically the gauge won't even move from normal until you are really hot. Given it's a 97, the HG problem sounds plausible and if it wasn't the problem when you started, running it at 3/4 on the temp gauge will make it an issue shortly. Do Robbie's overflow tank test yourself and his fan clutch test. It will take 5 minutes.
 
cruiserdan said:
Do the Robbie test:


Open the hood and start the engine. pop the overflow bottle cap off so you can see down inside but keep the end of the draw tube submerged. Have an assistant run the engine up to 3,000 rpm and hold it there. Watch for bubbles in the jar. Bubbles = blown head gasket.


FYI...

In my case bubbles would appear at idle speed. Sure enough, head gasket was blown.

Another visual test for possible head gasket leak is to look at the mating surface between the head and engine block. To do this, get on the drivers side of the engine compartment and using a flashlight, look at the seam between the block and head. Do you see signs of fluid leaking from there.
 
He's been hitting at least 226-228 since the A/C shut down. My money is on the head gasket.
 
Other than the scary HG suggestions, step back and check out the radiator and water pump. I vote for clogged rad.
 
Overheating while driving but not while idleing puts the suspicion toward a clogged radiator and away from a bad fan clutch as the inital source of the problem. As several have pointed out, if the head gasket isn't already blown it will be soon at the temperatures you are running. Have you at least lowered the coolant level in the radiator to expose the core and taken a really good look for crud? If you see clogs, don't bother "flushing" the cooling system--remove the radiator and have it cleaned or replace it.

Mike
 
Definetly points to the radiator...my fan clutch was bad and it didn't act at all like that, mine would get hot but only on long hard climbs, not normal driving.

The bubble in the resivour test is fun, might need a flashlight to see in there, and if your buddy revs the engine to 3000 rpms, the engine bay gets might loud and HOT, trust me. I thought I could almost make out one little bubble, but I decided it wasn't one, and after changing my fan clutch all problems gone.

I pulled my radiator and had it power flushed, cost about $45, they also did a flowtest on it, very cheap insurance IMO. How does the coolant look? Is it fresh at all, drain some yourself and see...did your old radiator cap have clay-like gunk on it? Bad sign if it did (mine did, which is why I pulled the radiator and had it flushed)...pulling the radiator is not hard at all, take a bit of time, just alot to disconnect.

Good Luck...
Mark Brodis
 
sjcruiser said:
I'd suggest the other Robbie test: grabbing the fan clutch (search the archive for procedures)

I ran a search on "fan clutch test", but wasn't able to run across it. Also looked on Slee's site, but no luck.

Any help?

Thanks,
Rookie2
 
Rookie2 said:
I ran a search on "fan clutch test", but wasn't able to run across it. Also looked on Slee's site, but no luck.

Any help?

Thanks,
Rookie2


Robbie's fan clutch test is good one but with the risk of loosing your fingers or worst spend the $$ and just replace it. The time you spend getting together the help and doing the test you could replace it. It will be cheaper than new fingers.

Phil
 

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