ryanbeezle

Firstly: I've read through dozens of forum posts on this topic, but there are some things I need clarification on.

My 96 ES300 overheats after a couple minutes in stop-and-go traffic, but runs cool at highway speeds. Turning on the heater full blast helps drastically with keeping the temp cool, but it only delays the overheating.

So far, I've had the thermostat replaced several times, then the radiator cap as well. Coolant level is fine and power steering fluid is full. It's possible that there's a cracked head gasket but no mechanic out of the several I've encountered recently have suggested that, nor would I be willing to spend the amount required for that.

When it comes to the specific behavior of the fan, it's like this:

When the temps begin rising, the fan will increase to a very fast speed for a couple minutes, helping to keep cool. Then at some point, the fan cuts off and the temps slowly start rising. I've observed the fan in this situation and was able to stop it with by hand because it was so slow. Sometimes the fan will rotate in sync with engine RPM, but that doesn't help much against the overheating.

The last mechanic was adamant that the hydraulic cooling fan motor is the culprit. He said that he ran plenty of tests to come to that conclusion. I've just had trouble finding the part at a reasonable price, as it goes for $500 and up. I want to be 110% sure before dishing out the kind of money.

However, most of the forum posts I've read about this topic never suggest that the fan itself is at fault. They suggest something about a solenoid, a connector to the power steering pump and jumping OP1 and E1 to test the fan.

When it comes to the connector/solenoid, I'm having trouble finding those. As far as the jump test, I tried sticking the ends of a paperclip into those holes while the engine was running but it didn't change anything. Maybe I did something wrong.



Anyone have any suggestions that will point me in the right direction?

Rcboi96

Put on a new power steering hose http://www.rockauto.com/catalog/x,ca...00%2B3.0L%2BV6 you might need to translate it to English for some add reason now, but i always ge my parts here, it's cheaper, new.

Rcboi96

idk i didn't read it all but just check it lol >_<

ryanbeezle

Thanks for the response.

I guess the best thing to do is just knock out the hydraulic fan to get that out the way.

After you recommended that used parts website, I realized that I don't really need to go scouring junkyards, nor pay a ridiculous premium for new parts- there's plenty of online resources for used parts! I ended up ordering the part from uneedapart.com for about 80 bucks and could have gone even cheaper from other websites.

Once I get this hydraulic fan motor replaced, I'll post an update here about the results.

ryanbeezle

I received the replacement hydraulic fan motor and got it replaced. There's a noticeable improvement in the fan performance, but I did notice the temps start to climb after some stop and go driving. I afterwards got the oil changed/topped off since I was running low (and that makes it overheat), so I wanted to eliminate that from the equation. I'll do some further testing to see if the fan kicks in at higher temps.

ryanbeezle

Still overheats, generally under 30mph. Now it seems to stop just before the red rather than blaze past it, though I haven't tried to push it any further. At least I feel some air flow now when I put my hand in front of it.

It's actually behaving the same as before, but with slightly better air flow.

I tried jumping OP1 and E1 but there was no effect.

I'll do more research, then take it back to the mechanic in the morning.

LeX2K

May sound obvious but you need to find out why jumping the service terminals doesn't cause the fan to race at full speed. Perform these checks and report back. Are you going back to the same mechanic that was "adamant" the cooling fan was at fault?



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ryanbeezle

I appreciate the response Lexus2000.

I agree 100%. The fact that jumping the connectors has no effect points to an electronic issue. I'm thinking it may be the solenoid or ECU.

I read a post where someone had an identical issue with their fan and they simply had a connector unplugged from the PS pump. I want to check the connector, but I can't locate it with certainty. Just about any es300 cooling system diagram, I've looked at it- they're just difficult to use as reference when I don't know how it looks in real life.

Concerning the ECU, what do I need to test it? Some device to read the signals? I'm a hard case newbie with cars, but this has been a heck of a learning experience.

The power steering fluid is maxed.

CUMan

We have had overheating problems twice with my wife's 94 ES over the 20 years we have owned the car, and both times it involved the connector between the ECU and the power steering pump.

I have not personally fixed the problems and cannot tell you from personal experience how you can make sure that this is the problem. However, if you don't see a fan speed increase when you connect the two terminal points, it sure sounds like the "speed up" signal is not getting to the PS pump.

The connector from the ECU (under the glove compartment) and the PS pump comes through the firewall and plugs into the PS pump. Looking at the diagram in the Haynes repair manual, the plugin point appears to be at the top of the PS pump next to the PS fluid lines connection points.

You likely cannot see this connection looking at the top of the engine. However, if you remove the right front wheel and the inside fender apron, I suspect that you could see it then. Look for a wiring harness coming through the firewall. If it is hanging loose, or if the harness is damaged in some way, you likely have found your problem.

ryanbeezle

Thanks CU.

Well I won't be able to take the wheel off myself as I don't have the tools.

The mechanic just called and said that it may be the thermostat. I've gotten that replaced 3 or 4 times in the last year, so I don't think that's the core issue.

He said that he did the diagnostic test and it worked (the fan sped up), so I'm having conflicting thoughts. I'm going to go back to the mechanic with the problem reproduced so he can see that the fan should be faster. He wants to check the pipes to confirm that the thermostat is working correctly.

I just don't get what would make a thermostats fail so often.

I've been running all of my research by him but he says he checked all of that stuff.

I'm open to the idea that there's multiple variables at play, but I know one thing for sure... The fan should increase with temperature and it does at first, but then it winds back down to normal speed while temps raise. I really don't believe that it's supposed to do that.

More updates soon.

ryanbeezle

The problem was the temperature gauge and the fan is indeed kicking in when it's supposed to. After the fan motor was replaced, I didn't let it get warm enough for the fan to kick in. It's a beastly fan indeed.

The mechanic measured the temps and they were at normal range when the gauge was in the red.

Somewhat relieved, but I'll get the gauge fixed next week.

mtnman82

My daughter has a '96 and is having overheating issues when in traffic, the drive thru, etc. I'm thinking it's the fan because she drove home 10 miles after this happened the last time, popped the hood to call me when she got there and told me it was too hot to sick her arm under the hood. Truly wish it was just the gauge, but is sounds to me like things are getting really hot.

Can you please tell me where I can find OP1 and E1 so I can jump and test the fan?

The search function is not working on this site for me presently (I repeatedly get a 'can't display page' error).

Thank You!

Edit: got it - port next to the intake manifold?

CUMan

Open the hood and look toward the back on the passenger side. Just to the left of the intake manifold and about a foot forward from the firewall will be a small black box. It is probably about 1" X 3". It will be to the right of the top of the suspension strut.

The cap on this box will open up, and you will see numerous ports inside. A paper clip can be used to do the test.

ryanbeezle

Update:

The fan... works. After so long without a working fan, I had forgotten how loud it was supposed to be.

But as soon as one problem is squashed, another arises. I noticed the temp gauge rising on the freeway. I ignored it for a bit since I had concluded the the temp gauge was defective. Then I noticed the coolant bubbling. Still- I figured that was OK. Then once it was boiling to the point of vapor, I got the clue- it was actually overheating, so I think the temp gauge may be somewhat accurate if not entirely.

I'm thinking that I've been low on coolant ever since I got the fan fixed- hence the gauge would raise even with good air flow after a couple minutes on the freeway (I didn't have that problem before). The overflow tank was full so I wrongly assumed that the whole system was too. I would hear loud bubbling from the overflow tank after shutting off the engine- that would last for minutes- not because just from boiling, but because the return line was pushing back air. It's gotten progressively worse- overheating within seconds of starting the engine and driving.

Last night, the coolant was bubbling as soon as I got off the freeway. Temp gauge was beyond red. I noticed that the overflow tank was practically empty from spilling over. I afterwards added fluid directly to the radiator to make sure it was circulating, Still overheated, but probably because I didn't let it cool long enough... or something else

Today I topped it off and went about 15 miles from a cold engine- a mix of highway and stop-and-go. No immediate signs of overheating and the fan kicked in at normal temp... And no bubbling. This is the first time I've been able to do that in a while.

To be honest, I get nervous when I DON'T see overheating because I've had this problem for so long now. Either the issue is resolved or a big storm is coming...

To be continued...

BK4293

Does your model have the connector on the top of the power steering pump. Stick your hand in there and feel around.

I had the same issue, from my understanding when this plug is disconnected the fan never goes in high speed.