Engine cooling issue - Toyota Nation Forum : Toyota Car and Truck Forums

uuuuu · 09-02-2008, 08:43 PM

Hey guys,

I've got a problem with my cooling system. After a 1 hour drive on the freeway, I was sitting at a stoplight and I noticed the temp gauge going up towards the redline. I opened up the hood and noticed that the radiator fans weren't spinning. If I turned on the A/C, then both fans spun just fine. What my mechanic did was disconnect the fan switch so that they run all the time, and I will get that replaced soon (don't think it's a thermostat issue because hot coolant enters the radiator grid). Coolant levels are fine, but even with the fans on all the time, after (and to a lesser extent, during) a freeway drive the temp gauge increases to ~80% of redline. It will go up and down at times (not suddenly, but gradually). No CEL or abnormal behavior otherwise. Any ideas of what it could be?

Kep · 09-03-2008, 11:31 AM

When everything is hooked up correctly and no AC running then one fan should cycle on and off with the radiator temp. There is a temp sensor for the fan located on the radiator to control this. That sounds like it failed. With both fans running all the time the temp shouldn't get 80% hot. Sure sounds thermostat related. Easy to test or remove completely and see if there is an improvement. If there is, get a new thermostat. Also, could be the dash temp gauge or its sensor is bad and giving you too hot of a reading. Use a seperate temp gauge to check.

Kep

N35QU!K · 09-03-2008, 12:03 PM

I agree with Kep on this one, that's most likely a temp sensor problem. I had a similar experience with my temp gauge, but that was only because I was leaking coolant xD

uuuuu · 09-03-2008, 10:17 PM

So if it were a thermostat issue, would the upper radiator hose get hot like it does? Or maybe the thermostat is only partially opening? I'll get the thermostat inspected too, thanks.

Dave's · 09-04-2008, 01:35 AM

I'm not a professional but it could even be a water pump on it's way out. I've heard of the fins coming apart as not all are metal any more. But sounds like there are definitely other problems as well.

uuuuu · 09-04-2008, 10:44 AM

Now that I think of it, the timing belt/water pump is due for a replacement (60k+ miles). Do any of these problems trigger the CEL?

***new echo owner*** · 09-04-2008, 10:51 AM

Water pump and timing belt don't trigger CEL.

What is the year of your car? Four r six?

N.E.O.

uuuuu · 09-04-2008, 11:17 AM

1993 SE 4 cylinders

***new echo owner*** · 09-04-2008, 11:30 AM

Did the fan ever come on by itself? Have you check the radiator to see if the temperature are fairly even all the way across, hot on one side and gradually cool down towards the other end? No cool spots in between?

If the fan does come on by itself, then your switch is working. A plugged or restricted radiator will cause increase in temp even with the fans going and coolant circulating.

N.E.O.

msm15 · 09-05-2008, 12:00 AM

HI Glad to see I am not the only one having this problem, well not really, but I have the same issue after a long drive if I shut off the ac. the engine temps start to go up. I recently had the head gasket redone, a new radiator put in, and I just installed a brand new toyota OEM thermostat so it isnt a termostat issue. I flushed the radiator after the first time it happened. When I popped the hood and checked the radiator - 3k miles after the new head gasket and radiator, I noticed that it was all brown inside - the coolant looked terrible and it was short a little less then 1L of coolant so I flushed the system completely - at that point I checked the thermostat (which oddly enough I had been driving the car since I bought it, with out a thermostat, when I open it up there was no thermostat !!!) I put in a toyota thermostat filled up the radiator and over flow and ran the car for another couple hundred miles before it started acting up again. I popped the hood again and it was low on coolant again this time only a drop but the over flow was almost empty ???? so now what where do I go from here ?

***new echo owner*** · 09-05-2008, 12:17 AM

Quote:

Originally Posted by msm15

HI Glad to see I am not the only one having this problem, well not really, but I have the same issue after a long drive if I shut off the ac. the engine temps start to go up. I recently had the head gasket redone, a new radiator put in, and I just installed a brand new toyota OEM thermostat so it isnt a termostat issue. I flushed the radiator after the first time it happened. When I popped the hood and checked the radiator - 3k miles after the new head gasket and radiator, I noticed that it was all brown inside - the coolant looked terrible and it was short a little less then 1L of coolant so I flushed the system completely - at that point I checked the thermostat (which oddly enough I had been driving the car since I bought it, with out a thermostat, when I open it up there was no thermostat !!!) I put in a toyota thermostat filled up the radiator and over flow and ran the car for another couple hundred miles before it started acting up again. I popped the hood again and it was low on coolant again this time only a drop but the over flow was almost empty ???? so now what where do I go from here ?

Well, you might have an entirely different situation comparing to OP. When you replaced your head gasket did you have the head check for warpage and pressure test for cracks? How about the block itself, was there any warpage? As for where the coolant went, you will probably have to pressure test the coolant system and look for possible signs of external leak. If there are not external leak then you will have to check for internal leak. Does you car seem to have excess steam coming from the tailpipe when first start up? Slight roughness when it first start up? Check your plugs and look for signs of burning coolant, a glassy looking plug is a sign. Those are symptoms that you can look for. You can also do a block test, and see if there is combusterble gas entering into the cooling system. Oh, brownish coolant is also a sign that combustion gas MIGHT be causing some problem there.

Well, can't think of anything else right now, but those will take up a little bit of you time if you descide you want to look into it.

N.E.O.

uuuuu · 10-09-2008, 10:08 PM

Hey all, thanks for the help, I had the thermostat and radiator fan switch replaced and all is well!

I think the thermostat was only partially opening, so that some coolant was flowing but not enough. That explains why the radiator was not effective at cooling the engine at highway speeds, even without fans running.

The fan switch would explain why the fans weren't running.

$50 for parts, total cost ~$150 (which may be a bit steep, but my mechanic helped me out a ton so I'm glad to pay it).