Head Gasket Soon?

[Lex3486]

I'm aware that head gaskets are a common problem on Supras/SC's. (Apparently on older ES's too, but that's a different story...) Anyway, my car has, on a rare occasion, done some funny things since I've owned it, and I'm starting to wonder if maybe a head gasket is in my future. First off, since the first time I ever looked at it, I've noticed that it doesn't idle as smooth when you FIRST start it up as it does once the engine is warmed up. Another thing is that on an extremely rare basis, the idle will drop below normal until it's at about 500RPM and it feels like there's a miss. However, the split second you give it a little gas, it responds just fine, but once it idles back down, the same thing will happen. Then, next red light, back to normal...The third thing is that from time to time, with the engine warm and the A/C off, the heater will blow cold air for a while and then, for seemingly no reason (and I've tried to make some sorta connection as to what triggers it but can't really find one) turn hot and stay hot until/unless you turn the thermostat down. The last thing that really has got me thinking about this is that in the 25k miles I've owned it (now up to 155), it's gotten a little too warm twice, and I believe that I pinpointed the cause to a lack of coolant in the reserve tank. It just seems to be disappearing, but not out the overflow hose-somewhere else...I've not noticed any oil in the coolant, although it is quite dirty (I plan to flush it once the weather warms up) and no coolant or moisture buildup in the oil or on the dipstick as my dad noticed on his old Supra just before head gasket time. It also doesn't smoke or have a peculiar exhaust smell. I replaced the plugs a while back and they all looked perfectly normal, albeit a little dirty from 13 years of driving. SO, all that said, what do you guys think? Anything sound familiar? (sorry for the long post...just wanna be precise)

[LexusTech117]

Do a compression test just to be sure. It sounds like you have most of the symptoms of a Blown Head Gasket... It's possible your thermostat could be acting up also. However, that would not explain the loss of coolant when you're not losing it through the overflow tank. Keep an eye on the level of the fluid in your coolant reservoir.

-Dave

[monarch]

Take your car to any shop you trust and ask them to do a chemical test on your coolant for a blown head gasket. The other good test involves using an exhaust sniffer at the coolnt recovery bottle, if there is a leak it will show up by reading the exhaust in the vapor coming off from the coolant. Headgaskets can leak internally or externally; coolant into the cylinder area, coolant into the oil, coolant seeping down the outside of the engine block as a coolant leak (sometimes evaporating before actually leaking onto the ground), exhaust leaking into the coolant or oil, oil leaking into the coolant or showing up as an oil leak.

A blown head gasket is a symptom of preventive maintenance neglect or maintenance performed with aftermarket parts and fluids. If spark plugs were not changed in 13 years I would imagine alot of other tune up type maintenance on the car has been neglected as well; e.g distributor caps / rotors / spark plug wires / cleaning of the throttle plate, etc. that could explain the erratic and rough idle.The cooling system might need a new thermostat, thermostat gasket, radiator cap, antifreeze, the internal radiator core tubes checked for mineral buildup, exterior fins cleaned of dirt and bugs, electric cooling fans checked for proper activation. Preventive maintenance is highly effective only if performed preventively, using Toyota parts and fluids. In your case, you might still be faced with corrective repairs (i.e. a head gasket job) even if all the above preventive maintenance is performed, but the maintenance would prevent future failures.

[Lex3486]

Well I got the impression from looking at the service records that the car was always well cared-for; it's had all of the scheduled maintenances, performed at the Lexus dealer, up to the 85k(?) mile service. Anything and everything that ever broke on the car was repaired at one of 2 Lexus dealers, one of which is mine. Sounds like I got a few things I need to check on though...