02 Tundra Overheating/Wiring problem

Hi everyone Im Stefan & I'm new here. I have an 02 tundra SR5 4.7L V8. It's got 296,000 mi on it and still runs like a champ. But I've been having trouble with it overheating, particularly when in traffic or when there's no air flow. I noticed that my cooling fan wasn't turning on so I replaced both the coolant temperature sensor and coolant temperature switch, I put in a new thermostat and a new fan clutch and a new heater / cooling fan relay. And it's still doing it. So I was out therewith a test light checking my fuses and it seems a whole section of my fuse box does not have power. Specifically all my smaller fuses. Which would explain why the signal isn't getting from the relay to the cooling fan to turn on. How do I find out if it's a short in my relay / fuse box or if something more sinister at foot? The box does have power and there are several relays/fuses that are working but then there's a whole section that isn't. Any advise would be greatly appreciated!
Stefan M

 

Cooling fan is tied to the fan clutch up front from the factory, it's not using voltage/power.

Did someone install an electric cooling fan on your Tundra?

(PS - this would be one of many reasons it's not ideal to have electric cooling fans...)

 

Interesting. My 2001 Sequoia has a factory towing package with clutch fan and auxiliary electric fan. Figured the Tundras were the same.

 

I had to double take, make sure it was a Tundra.

 

Nope no electric fan. The only fan I have is attached directly to the fan clutch

 

When was the last time you did the T-Belt/water pump? Radiator in decent condition? You have good coolant levels?

 

What is the history on the radiator, ever been changed or flushed ?

Kind of hard to see due to the A/C condenser coils but can you see any blockage on the radiator or considered cleaning not only the A/C condenser coils but the Rad coils also.

When you first start the engine on cold start, do you get the fan roar for 10-30 sec ?

Agree it's unlikely related to overheating but how were you testing, with engine running or with IGN ON only or no key in ignition ?

Also, which fuses below are you speaking of ?

 

Gotcha. It should be spinning all the time, any time the engine is running. A lot of things will cause overheating.

As stupid as it sounds, one of the more notorious things that fail is your radiator cap. It needs to pop open to allow overflow into the canister. Don't buy cheapies off the scAmazon/fleaBay/WallyMart sites, ideally get OEM, you'll probably not need to change it again for another 10-15 years.

It's pretty easy to test if your fan clutch or its bracket (since the 2UZ/V8 on these trucks, the clutch sits on a bracket+bearing, not on the water pump) is bad or not. When the engine is hot, pop the hood, try to spin the fan by hand. If you can throw the blade and get more than one rotation out of it, or it spins freely, the fan clutch is bad. There should be some resistance on the fan (more when hot than when cold). You also shouldn't be able to rock/wobble the fan, that's a sign the bearing on the bracket is bad.

Not properly burping the system can cause overheats.

Not installing the thermostat with the jiggle valve at high noon (anywhere 1 o'clock to 11 o'clock can be acceptable) for the V8.

Blockages in the system aren't common, but we've seen it when fluid colors get mixed. Your truck should be running pink (or for older models, potentially red) coolant, not green, yellow, purple, orange or any other color.

Water pump going bad can cause overheats also. Toyota recommends changing the water pump and belt tensioner at the same time as the timing belt on these trucks. They recommend to change the timing belt every 90k or 9yrs, whichever comes first. 100k miles and 10yrs is fine, but these are low interference engines, so you DO NOT want to skip this particular piece of maintenance, and always use the kit Aisin sells (TKT-021) to do the job, it includes all the stuff you'll need.

 

PS, this guy actually does decent videos on diagnostics, sometimes people find videos easier to ingest than words.

Just know: Unfortunately, this video covers an engine where the fan and its clutch are integrated into the water pump. The V8 (2UZ) in our trucks isn't this style. But the rest of it is pretty solid info.

https://www.youtube.com/watch?v=lKJ2ri6-YLo​

 

So it seems like this whole section of fuses it relays is not functioning. I've tested the relays they are functioning. I've burped the system for any air in the lines. I put in a new thermostat in. I've changed the fan clutch, both thermostat sensors and sending unit. The only thing I haven't changed is the water pump but I think it's functioning. I think that everything's functioning up until it gets to the relay that's supposed to turn on the fan but it's not getting that signal because the fuse box doesn't have power for some reason.
In the picture it seems like this whole section of fuses is not working even though the fuses themselves are not blown or the relays

 

My fan only turns couple times when I turn the car off so I know it's not the fan clutch. The fan does run High when I first turn it on for 30 seconds or so.The fan speed does increase when I turn the AC on low medium and high. But I don't hear the fan kicking on when my car's at temperature and it's supposed to be. kickin' on.
I did put a new thermostat in but I've never heard of a jiggle valve so I guess it could be a possibility that that it may not be facing 12:00. I put a new radiator cap on it as well. It Doesn't seem to be leaking coolant either.

 

Also when my trucks at temp and i accelerate you can hear the fan spinning at the speed of my acceleration. so if I step on the gas the fan spins harder and you hear that loud blowing.

 

I don't know if this is related but also my 12 volt DC power outlets also have stopped working. Also I forgot to mention this so I was driving the other day and my truck was hot but the thermostat started glitching real spastically and sporadically & Very quickly. Like there's a short in a wire or something. It was way too quick for it to be sensing a change in temperature. Which is why I think it's an electrical issue, maybe there's a short somewhere or maybe something's grounding out. But that's one area of my vehicle I know very little about

 

Speaking from recent experience, that can be air in your system. After a rather sudden coolant leak developed, I refilled my radiator and things were mostly fine. But every now and then I'd get an overheat scenario in the blink of an eye. I watched my temp gauge shoot up to H in a fraction of a second. Mostly in stop and go scenarios. Truck would never overheat while underway, water pump doing its job.

Long story short I had a large air pocket in my system, everytime that pocket of air would sit on my temp sensor, it'd report overheating. Fixed my leak, did a drain and fill, properly burped the system, all good now.

My only other thoughts are maybe a severely clogged radiator/something impeding air flow. If your fan is properly spinning, it's not your issue.

 

Awesome. Thank you. How can I determine if my fan is spinning when it needs to andhurt just when my AC blower is on? And I shall burp my engine coolant again, just to be safe.

 

As shifty mentioned above.

"It's pretty easy to test if your fan clutch or its bracket (since the 2UZ/V8 on these trucks, the clutch sits on a bracket+bearing, not on the water pump) is bad or not. When the engine is hot, pop the hood, try to spin the fan by hand. If you can throw the blade and get more than one rotation out of it, or it spins freely, the fan clutch is bad. There should be some resistance on the fan (more when hot than when cold). You also shouldn't be able to rock/wobble the fan, that's a sign the bearing on the bracket is bad."

Alternatively, roll up some newspaper and stick it in the fan when the motor is running and hot. If you can stop the rotation of the fan, the clutch is bad. Watch your fingers.

 

I feel you need to understand our mechanical fan somewhat better and re-read some of the above posts starting with @shifty` 1st post to the thread....there is no fan relay.

The following is definitely an electrical issue BUT possibly unrelated to coolant....not quite convinced their 100% related.

Best I can surmise from what you've circled definitely appears you have a glitch from 120A fuse onward.
If there's more in your checks that I have not highlighted in red, speak up please.

• Power Outlets active via PWR Outlet Relay closed contacts 1&2 protected by 120A fuse
• Temp Gauge fed by 10A Gauge fuse which is eventually protected by 120A fuse

 

I will ask a stupid question at this point. Could your symptoms be an indicator of a bad gauge reading high temp in error?

 

Personally, he has certain electrical AND mechanical issues, so I don't feel that's a stupid question, considering the gauge problem is either mech or elec or possibly both.

However, the gauge itself being flaky will not affect the Power Outlets among a few other items he circled. Of course, not 100% sure which particular circuits without @SpartStef being just a little specific.

My other question remains from my initial post...."how were you testing, with engine running or with IGN ON only or no key in ignition"....because it matters !