Yet another overheating problem, please

My 1990 Lexus ES250 (aka Camry V6) has had an annoying but not fatal cooling problem for a couple of years, without any significant change.

The car runs flawlessly if the outside temperature is no higher than say the mid 80's or maybe a bit higher, but when it gets into the 90's or higher, it's really marginal.

Usually the first thing that happens when it's hot outside and I drive up a shallow grade (after a half hour at freeway speed) is that the aircon stops cooling. The temperature gauge remains at its normal point, where it's run within a couple of needle widths since the car was new. I get off onto (flat) surface streets about that time on the way home, and in about 5 minutes the aircon usually comes back on. When I pull in to the garage, if I shut down but turn the ignition back on (the Lexus fans don't stay on with it off) the fans stay on high for five or ten minutes, then drop to low for a couple of minutes.

Today it was near 100, and the aircon actually shut down much earlier, on a section of the road that you'd have to know to realize it was climbing a bit. It came back on after a few minutes. Then at the hill it shut down and for the first time I can remember the temperature gauge climbed to about halfway between the normal point and the red line. I took it relatively easy up the hill, but it stayed at that temperature the rest of the way home. I left the fans running and it cooled off fairly quickly. I figured I'd lost a lot of water, but in fact it didn't seem so, although I refilled the expansion bottle after while.

The water pump was replaced a few years ago, and at least isn't leaking. The thermostat is just a few months old, genuine Toyota part fwiw. No water in the oil, and mechanic thinks engine problem is unlikely since he thinks gasket/block problem would show the problem even at normal outside temperatures, not just when hot.

The only other symptom I can think of is when I turn the heater on there's a "waterfall" sound especially if I accelerate up a ramp.

My present prime suspect is the radiator, for no good reason other than it was cheap.. It's an aftermarket replacement I got several years ago when the plastic tank on the oem cracked. I'm thinking perhaps I shouldn't have bought it from the guy who gave me the cheapest price on the phone. It was okay for a while, of course, otherwise I would have taken it back and had a word with the installer.

Thanks for your comments.

Reply to
JT
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Have you ever opened the radiator cap and looked in the radiator? You may have a full expansion tank but your radiator might be dry.

I didn't really see anything that said you checked it so I figured I'd mention the simple things first.

Reply to
Bruce Chang

How often have you changed your antifreeze, How often has it been completely flushed. Do you have an air bleed on the motor. Do you run a 50-50 or less mix A new thermostat doesnt mean it hasnt gone bad. Try a professional flush, a 25% antifreeze mix, New thermostat. Look at your radiator to see if visible buildup is evident .

Reply to
m Ransley

If the fan kicks on when it should, then I'd replace the radiator. It was probably marginal to begin with and is now partially clogged.

Reply to
JimV

Does the lexus have a bleeder valve for removing air from the heads? Would explain the waterfall sound.

Reply to
TCS

Using a greater than 50-50 antifreeze mixture will reduce cooling-heat transfer. Test mixture and try reducing it to 25 antifreeze-75 water by adding distilled water. Do both cooling fans run, one or both should come on when the AC is turned on. Do fans come on when motor is hot. The pressure cap on the radiator should be replaced it may open to early.. Water pump belt may be bad or out of adjustment . Engine timing my be advanced, does the motor knock on acceleration. The cheap radiator may be bad or to small or defective, or clogged.

Reply to
m Ransley

Thanks. There's a bolt up on the engine that's supposed to be at the high point that you're supposed to back out to release air, but I haven't gotten anything out but water. The service manual doesn't mention anything about otherwise-trapped air in the cooling section. I should look to see if the heater itself gets discussed in a different place.

Any recommendation for a top-quality radiator? A lot of them just seem to compete on price, and that isn't necessarily a mistake I want to repeat. The only variation I see is that one outfit sells two different kinds: one is like the oem and has the plastic expansion tank (not my favorite, but if it lasts a few years without cracking and meanwhile does the job, so be it). The interesting thing is that they advertise "copper and brass core" or something like that. Their other choice is merely "all metal". Both cost about the same, fwiw.

Reply to
JT

Good enough question, but yup, the radiator cap is doing its to and fro thing properly and the radiator is full of liquid.

Reply to
JT

Thanks, ransley. Changed antifreeze with new thermostat, of necessity, maybe six or nine months ago. No agressive system flush then, though.No particular crap in the water. I generally run about 50-50 (Lexus actually suggests 70% antifreeze) but don't make a science project out of it. Temp guage zips up to operating temp in the first five minutes of driving and stays there. You don't quite have to pull the engine to replace it, but it's not like it used to be, so I don't think I'm quite ready for a new one quite yet. No obvious buildup, wish it were that easy.

Reply to
JT

Thanks. I thought ethylene glycol was better at heat capacity and transfer than water.

Both fans run fine afaik, although I don't think that merely turning on the AC turns on a fan. They appear to behave properly when the water is hot. Radiator cap is relatively new and didn't do anything too different when it was brand new.

Remember, this problem has been going on for several years - the machine works fine if it's 80 degrees or less outside, which even in LA is most of the time, and even when it's hot I have to run at speed for 15 minutes or so and then climb that little hill to even get the a/c to go off. Yesterday it was a bit over 100 and I had to pick the kid up from school, longer than my usual afternoon drive. The temp gauge going above the normal point got my attention as it hadn't been doing that - I figured I'd lost a lot of water and was surprised that wasn't the case.

I'm certainly inclined to replace the radiator - relatively cheap thrills - and appreciate all the feedback. Everyone please tell me who makes great radiators and who to avoid.

Reply to
JT

Water dissipates heat much more so than antifreeze, on pure antifreeze motors do overheat and less heat comes out of your heater during winter. On my 91 Camry and I beleive others the fan should come on as soon as you turn on the AC You do keep the expansion tank filled to the proper level, im sure. You can remove some radiator fluid and then check the coils for any contamination. I would then add water only. Using Redline Water Wetter you can run a 25-75 mix. Check your pressure cap at a serice station to see if it releases properly.

Reply to
m Ransley

Reaching operating temp in 5 minutes is real fast, mine takes 10-15 . your thermostat may not be opening fully. Use a toyota thermostat only , i have had alot of bad ones, they dont last on other brands. You check it in a pot of water with a thermometer.

Reply to
m Ransley

It may also be indicative of his cooling problem.

The AC turning itself off is another symptom the cooling system is overtemperature. The exact mechanism maybe increased head-pressure due inadequate condensor cooling (the cond sits in front of the radiator) or the ECU simply responding to the temp sensor. In both cases we are still in the dark as to why the car is overheating.

Provided the headgasket is not leaking and thus allowing compression and/or exhaust gas to vent into the water-jacket, pushing water past the radiator-cap pressure valve AND therefore reducing the volume of coolant in the engine, then we get back to the following:

- failure of the coolant recovery system with resultant loss of coolant volume.

Should be evident as low coolant levels in radiator with or without coolant in the overflow/expansion bottle. Ckeck for worn of damagedseals in the cap, split or loose expansion-tubing to the bottle.

- a leak, causing loss of volume

let car heat-up with a full system while checking for coolant on the floor or wetness around the block-hoses-rad etc.

- scale/ rust blocking the radiator

Flow-checks are not always a good test. If there is doubt about the radiator, the tanks need to be removed for a core inspection or a recore/new radiator not 2nd hand.

-malfunctioning thermostat

These can be intermittant,but not usualy so. Replace if suspect, they are really cheap insurance. Fast heat-up times can indicate the thermo is sticking partially closed or is binding as it tries to open. I've seen thermos go from good to staying partially shut beyond boiling temp (at atmospheric temp). A few have come new this way,...buy genuine or a reputable brand.

- airflow through radiator reduced due to core or AC condensor fins blocked with debris or flattened.

self explanatory

-scale/rust buildup inside the block water-jacket causing coolant flow and/or heat transfer problems.

This can be a real sleeper. Fortunately for it to become a significant problem, the cooling system needs years of neglect, in which time usually the alloy head has thrown in the towel.

- inadequate water-pump performance due incorrect impellor clearance or the impellor not fixed to its shaft

another hard one to check and is usually done last. Checking coolant volume washing thru the engine is difficult due to the constriction on flow by the thermo.

Jason

Reply to
Jason James

Are you experiencing this problem only when A/C on? I've experienced a similar one two weeks ago when in a Jammed traffic with A/C ON, engine cooled down to normal range once I got off jammed traffic. I've tried it again, and yes, it correlates to A/C being ON.

Test drive your car with A/C off in same conditions you experience the symptoms.

P.S. timing (advance/retard) is affected when A/C is on which impacts what you experience.

Reply to
IceMan

The waterfall sound makes me wonder if there is air in the cooling system. The radiator could be clogged internally if it is a few years old. It could also be clogged externally.... I had one car that developed these symptoms fairly suddenly. I had driven a long way at night when some kind of insect was numerous and the front of the radiator became plugged with dead bugs. When the sun came up and the temperature rose to the upper 90's the car gradually started to overheat.

Reply to
Tom Eisenman

I think you win the ring, Tom. The radiator seemed to flow okay, but it did have a tiny leak somewhere that apparently was sucking air back in when it cooled, instead of just sucking fluid back out of the bottle. I replaced the radiator, and the new one stays full to the brim like it's supposed to. We haven't had any mega-hot days since, but on medium-hot days it seems to be working much better. In particular, the a/c seems to be running colder/more efficiently. It feels different enough that I think it's fixed. There was an interesting collection of bugs in it, too, but I think the pinhole leak may have been the culprit.

Meanwhile, the heater doesn't work. I'd like to th>The waterfall sound makes me wonder if there is air in the cooling system.

Reply to
JT

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