ryanbeezle

1996 Lexus ES300

I've been having overheating issues for a couple of months now, so I know that HG's are a possibility, but the last block test I ran gave a negative result, plus I'm ready to get rid of this car if I can't find a low cost solution soon.

Overheating first showed up immediately after getting off the freeway (10-15 mile trip).

Since then, I've gotten the thermo replaced several times, and a new radiator cap... Still overheating.

Then I got the hydraulic cooling fan replaced... It helped only slightly... still overheating.

Recently, the upper radiator hose ripped open and there was steam/air coming out. Replaced it and now it doesn't overheat after getting straight off the freeway (at least on the 15 mile trip)... Maybe I've had a leak all that time.

I had my mechanic drain the system, add some red coolant and burp the system, just to be sure that it wasn't a factor. It helped slightly...

So I took it for a more rigerous test drive and found out that it overheats on the highway after roughly 25 miles. After that, temps start to crawl up. Sometimes the heater will blow warm air and reduce temps. Other times, it'll blow cold air and temps will continue to rise.

Both the upper and lower hoses are warm.

LeX2K

Possible causes are bad water pump, clogged cooling system and/or bad radiator. Does the hydraulic cooling fan pass the tests shown in the service manual? Why did your mechanic replace the thermostat several times that makes no sense.

BTW repeatedly overheating an engine can cause the HGs to fail, and a block tester does not always show positive when there is a head gasket problem.

Jarett

I'm not sure why your mechanic would have replaced the thermostat several times. no heat from the heater is a classic plugged heater core, or bad water pump symptom. Add that with over heating and It's probably 90% chance that it's the water pump that has failed.

Oro

We had exactly this cascade of problems once with the ex-GS.

Problem was the replacement Tstat was installed on the wrong side of the gasket. You can install it that way and it will seal, work, run, but overheat because the t-stat body hits a mold in the plenum and is only partially opened. Everything looks good, runs fine, tests fine, until you are full hot and it goes to pot.

Take out the T-stat and make sure the gaskets are all on the correct side. Sounds insanely simple, but it can create this. It may not be your problem, but it's hard to find a simple answer for such a problem.

Unless you have a '90s Lexus.

Did you check your heater valve on the firewall? They fail frequently on these vehicles. Bad design. Should not cause overheating if closed/open, but if it is partially stuck, it can create back pressure and mess with system flow. Could create these symptoms. That strengthening other parts of the system then led to the upper hose cutting loose means 2 things: a) the upper hose sucked and you or a mechanic should have put hands on that and ID'd/fixed it earlier, and; b) it's a pressure problem sending back-stream signals to where it is not. If you read that as a cause, you mis-read the difference between a symptom and a sign.

If you have a mechanic who suggested draining fluid and changing to red as a way to cure this, you should find a new mechanic ASAP. And get a refund. That's either complete BS, or a mechanic who does not really know his stuff. Red has a long-term effect on later models, but not 1996 if it has been run consistently with the same type fluid. That you were talked into that means you were chasing ghosts.

ryanbeezle

Thanks for the responses.

The reason the T-stat was frequently replaced was because I had been going to different mechanics and the first thing they all did was replace it.. so over the last year, I've had it replaced 3-4 times.

Having the last mechanic take care of the radiator fluid was my own decision. I wanted to take care of the simple things before going on to the big things. I've realized that many of my OH problems have centered around lack of fluid in the system. My primary concern wasn't using red coolant, but making sure there was no air bubbles in the system, as I've heard that it could cause overheating.

Concerning the water pump, I'm beginning to lean towards that as well. A previous mechanic said that there were no stickers indicating previous servicing, so it may have never been replaced. I'm at 125k right now.

I used to be able to go 50+ miles on the highway without problems (then of course OH after getting off the highway). Now I can no longer do that.

Concerning the fan, I've never successfully run the test myself. The mechanic said that he did, but I can't confirm. With a warm engine, I can hear the fan increase with RPM upon acceleration, but I rarely if ever hear it roaring while idle, even when overheating. I must be accelerating for it to increase in speed... So the fan might still be an issue too. But if I'm overheating at 60+ MPH on the highway, it looks like this problem stems beyond the fan.

ryanbeezle

So refilling the radiator was worthless. I found my overflow tank to be empty and the radiator needed another half-gallon. I had been driving for 2 days since last topping it off. Now I know... there's definitely another leak somewhere. I'm not sure whether it's happening while driving or over night, but I'll keep my eyes peeled.

jimijamz

ryanbeezle, oro mentioned the heater control valve. I am having that issue right now on our 95 es300. It has developed leak and loses quite a bit of fluid. Here is a picture of the heater control valve.
Have you seen any fluid/coolant on the driveway, ground or whereever it is that you park?

ryanbeezle

Update 11-7-14:

Thanks for the response Jimijaz. I didn't notice a leak near the HCV.

My leak is apparently near the overflow tank. here's a pic:



I'm still not sure exactly where the leak is, just the general area. When the engine is off, I notice air bubbles blowing out the the overflow cap/neck.