HELP 4.0L Overheating Issue

I’m reposting this from the 4Runner thread in hopes of getting some more input, it is the same engine after all...

Hey folks, hoping you guys can help me out:

Trying to help my sister out and I've been having some difficulty finding information on the topic. She just picked up a 2004 Toyota 4Runner Sport Edition, 4.0L, automatic, does have some some oversized tires on it, (285/70R17) and it has roughly 204,000 miles on it...

She's only had it for 2 days now, got a great deal on it and its fairly clean. She asked me to check out the rig, knowing I'm a Toyota enthusiast. I figured I could help out, so I got behind the wheel today and put it to the test. Foot to the floor, cruise control, heat/air conditioning, everything seemed great! Until...

She hopped into the driver's seat and I jumped back into my Tacoma, and we headed for a local trail. It's a long, paved, and uphill climb to the dirt. Once we hit the dirt, she switched the 4Runner into 4WD high, and we drove about 200 yards before I started to smell it overheating. We stopped and while we were sitting there deciding what to do, I watched the engine temperature climb almost to the red zone.

We decided to head back, and as soon as she took the 4Runner out of 4WD the temp started falling. By the time we hit pavement, it was back to normal and drove for the rest of the day at normal operating temperature.



Diagnosing the issue:

• I noticed the reservoir was almost full to the brim.

• The fan clutch was working properly, did the magazine test.

• Neither the top hose or the bottom hose had any pressure at all.

• No leaks from the radiator, any of the hoses, or the motor.

• Replaced the radiator cap, no resolve from doing so.

My thoughts:

• Maybe a stuck thermostat? Since there's no coolant flowing from the engine to the radiator.

• I don't think its a clogged up radiator, I was had squeezed the lower hose and got fluid to go into the upper hose.

• Maybe a bad water pump? They're a known issue apparently.

• Dare I say it, but maybe a head gasket?

Anyways, hoping somebody has had some experience with a similar overheating issue with the 4.0L. Anything helps guys, and thank you in advance for your input!

 

Have you checked the oil to see if it's contaminated with coolant?
Pulled the spark plugs to see it any are much cleaner than the others?
See any bubbles in the coolant reservoir?

The great deal part makes me suspicious. But, l could be wrong

 

Wouldn't be surprised if someone filled it with the amount it is supposed to take and didn't burp the system. Air can cause the thermostat to not open. Maybe they did a coolant flush recently? Is the coolant clean?

I was avoiding 03 and 04 V6 t4rs due to head gasket issues. Could be a head gasket and they filled the coolant to try and offset the coolant loss.

 

I don’t see how being in 4wd would cause it to overheat. I’m thinking when you went off pavement in 4wd you were going slow and for some reason while going slow the coolant wasn’t circulating sufficiently to cool the engine. Confirm that you don’t have a head gasket problem first. Then since it has 204000 miles it’s more than due for some cooling system maintenance. Because it has that many miles I’d just go ahead and replace the water pump, thermostat, upper and lower radiator hoses and flush the system. Did your sister get any maintenance records with the vehicle?
.

 

First off, thanks for the input fellas. We haven’t had much time to look into it just yet, but I’m gonna start here...

I consulted one of my coworkers who’s an engine-head, dude knows all. He concurred with this, no questions asked. He said that if it were a blown head gasket, it would smell like sweet burning and there’d be smoke coming from the tailpipe, both of which are not happening. Also, there is no leaks coming from the motor at all.

I’m really leaning towards the previous owner may have attempted a flush and didn’t bleed the system. We’re gonna do it proper next week or so, I’ll keep you guys posted.

Thanks again!

 

When my head gasket blew it would usually overheat after driving for a while then slowing down

-Water sounds in dash
-Heater only worked when I pushed the gas
-Coolant reservoir completely full and sometimes spraying out leaving empty rubber hose and low radiator

 

Also when mine blew it had no smell other than coolant. Passed every head gasket test I could find online. Put new spark plugs in and pulled them out after 100 miles. 5 were white while one was Covered in orange and brown

 

Kinda a mixture of odd symptoms. The thing about overheating in 4wd I’m uncertain. Maybe the front differential is putting an excessive load on the engine?

The cooling system I’d first grab the fan. Pull up and down, in and out. If it has a bunch of play it might be bad. Undo the belt to check it good, give it a spin, it should spin fairly freely with no notchyness. If that all checks out I’d check for exhaust gasses in the coolant. You need a block tester for this. Squeeze bulb that pulls air in from the radiator neck through a test fluid that changes color with a positive test(bad). Like what was already asked, if your reservoir is gurgling, pretty much says head gasket.

 

Not dismissing head gasket potential, but always start simple first

 

Yes, begin simple. Most times the problem doesn't require the most complex solution.

Check the coolant level in the RADIATOR.
Check the Thermostat is opening.
Check for radiator fouling. Debris on the front or in the fins.
Check the fan is working.
Check the water pump impeller. There have been instances with the coolant being corrosive to the impeller material.

Yes, a head gasket can cause an issue. Although, I wouldn't consider that as a first cause. Run the diagnostics and do simple maintenance on the cooling system. See where it leads.

 

First thing I would do before moving on to anything else, is confirm the coolant system is free of air. Could be a pocket trapped. Park vehicle so top of radiator is highest point.

Once that is confirmed, proceed with other ideas mentioned.

 

On my 2004 Tacoma, I had an overheating problem. Mine was caused by a clogged radiator. So you can check for that. At the miles the 4runner has, I'm sure the small passages in the radiator has been narrowing with sediments or whatever is in the cooling system.

 

Alrighty everyone! Today we did the thermostat, a coolant flush, and a system bleed. When draining the old coolant it didn’t seem like there was enough, and it was a little dirty. Did not smell of fuel/oil.

Upon starting it up, the hoses now have pressure!! Whereas before there was none at all!

Took the 4Runner for a test drive and put it under the same stress as before that started causing the overheating, and she’s running like a champ! The temp needle stayed middle the entire time!

In conclusion, I don’t think it really needed the thermostat, but it was cheap and did it anyways. I believe just the flush/bleed was necessary!

Thanks again everyone!!

 

Awesome you got it fixed, not such a terrible expensive fix too.

I’m confused about something. Putting it in 4wd it overheated, back into 2wd, it cooled down? I’m not a 4wd person so I don’t know, does it put a significant load on the engine enough to cause those symptoms? It seems a thermostat stuck closed, and low coolant would cause it to run hot however it’s being driven.

 

I think that when being driven around in 2wd at normal speed there’s enough air moving through the engine bay to keep the temp sensor reading normal. In all reality it was probably overheating all the time, especially since there wasn’t enough coolant in the system and the thermostat was stuck closed.

When put into 4wd, the increased load on the engine, plus low rpms and slow speed made for not much of a breeze into the engine bay, dramatically increasing the ambient temp. At least that’s my thinking of it!

 

Ok makes sense. Guess we don’t go 65mph in 4wd. After a warm it up cools down cycle, one more coolant level check, you should be golden.

 

I’m hoping for you, but don’t be surprised if it comes back

 

If it were me ,I would of replaced the radiator with the amount of miles on your 4runner has on it,really sounds like some of it was clogged .

 

Definitely still monitor things like the water pump and for any leaks. The coolant went somewhere. Judging by the colour of it though, it probably hasn't been messed with too much recently, which is a good sign that the PO maybe wasn't refilling it often. Glad it worked out though, but look everywhere for leaks. Check the passenger carpeting under the dash for heater core leaks. Hopefully the level stays the same now, but I would bet it got low from some sort of leak.

 

When you overheat the engine , you also overheat the auto transmission .
I would be looking at your transmission cooling system as a possible suspect as well