Still Overheating (Passed block test)

LittleCaesar said:
The next question is whether or not the tensioner was replaced with the TB/H20 pump. If there isn't enough tension on the belt to drive the pump fast enough then that could be a problem. I saw such on a Honda Civic not too long ago. The tensioner was maxed out, didn't keep enough tension on the pump and ultimately a bad head gasket occurred though the OEM pump itself and the OEM belt were fine.

No bubbles in the coolant until it becomes hot correct?
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Yeah, I think Little Caesar and I are on the same page here, it definitely sounds like the water pump is not functioning. Take off the timing belt cover and check things out, or try the idling when cold trick I posted back to see if you get any fluid flowing or not.

If you get some, but not much fluid visibly flowing at the top of the radiator (granted it'll never be a raging torrent but it should be noticeable), it might be the belt like suggested above. If no flow at all, your water pump is toast.

Also, this has nothing to do with your fuel delivery or filter. You can change it if you want but that won't make anything overheat.
 
I'm just gonna throw this out there. I think it's your head gasket. I understand that it passed the leakdown test, but the fact that it's intermitent (2/5 days) could be what lead to it passing the test. Headgaskets do weird things when they are fading.
 
No bubbles in the coolant. Only bubbling is boiling when it starts to overheat.

The heater seems to work every time, when I put it on high the temp comes back down to normal pretty quick. (I know this isn't groundbreaking).

I'll do the open cap, flow check today, I just wish I knew exactly how much flow I should be seeing.

...... I've don't a lot of this work myself, but I'm thinking getting the timing belt cover off to check the tension-er is (boarder line) outta my league.

I would do a timing belt and pump or a HG if I knew that's what it was, my concern is the fact that it may not be the issue. That is about exactly how much money I have to spend.
 
swapping the Timing belt and Water pump, along with belt tensioner is REALLY easy, it's ONLY time consuming. which is the BIGGEST cost of the job.

I recently did both (no tensioner) and the previous belt was gates (oriely) and the WP was OEM (looked original on my 97) the pulley had 'burnt' parts from the belt, and the belt was 'being frayed'

parts was $48 for toyota belt and $130 for toyota WP, I added other things in there, like toyota t-stat (NEVER run non-toyota t-stat) got everything from dealer...

on radiator hoses, Are they toyota?? I know some brands will collapse at high RPM (WP revs) when hot, Next time you boil, feel the lower rad hose (with rag, don't burn yourself) and have someone rev it, see if the hose is collapsing... if so, you have a clog or weak hose. I don't care how new the hose is.
 
The hoses are from Toyota. I have checked them when they are hot, but I have never had anyone rev while I check. Will do tonight.

I hope I'm not reading into this too much because I do not want to "throw off" everyone trying to help. But I check the hoses every day by hand (because fixing this problem has become my mission) and I do not feel like the bottom hose is substantially cooler than the top one. That said, we are talking about my hand, not a temp gun.
 
the1998sr5 said:
The hoses are from Toyota. I have checked them when they are hot, but I have never had anyone rev while I check. Will do tonight.

I hope I'm not reading into this too much because I do not want to "throw off" everyone trying to help. But I check the hoses every day by hand (because fixing this problem has become my mission) and I do not feel like the bottom hose is substantially cooler than the top one. That said, we are talking about my hand, not a temp gun.
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I think the only time the lower hose is colder than the top is when the thermostat is shut when the engine is warming up or seized shut due to corrosion/gunk. Otherwise it'll be pretty close to the same temperature as the top, just a tad hotter.
 
correct me if I'm wrong, but the lower hose should be substantially cooler than the top, the top comes out engine hot, and the bottom should be radiator cool, hence the reason the trans cooler is on the bottom, not to heat it up more but to cool trans down.

OP, it will only show true colors when you are 'boiling' and reving the engine... that should show you a 'failed' hose or restricted water flow, it will also confirm (if hose collapses) that your WP is in great working order... but you need to be 'boiling'... so be caueful to not over heat
 
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the1998sr5 said:
...
The heater seems to work every time, when I put it on high the temp comes back down to normal pretty quick. (I know this isn't groundbreaking).
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I wonder if the heater control valve isn't negatively affecting the 'standard' flow somehow? :cowboy:
 
Substantially cooler is relative given the coolant temp is still over a 150* and it's in a 200* engine bay. Without a temp gun on it you'd be hard pressed to notice a substantial difference in temp.
 
I am going to say to pull the cap and make sure the gasket is good. As others have said, OEM out of the box doesn't always mean it is good to go.

If turning the heater on brings down the temp then I would say the coolant flow in the system is fine, except that if the belt doesn't have enough tension on it, the impeller can't spin fast enough to cool the engine. You may be able to see if the tensioner is maxed out without removing too much.

I take it you had the overheating issue and then added the Water Wetter for good measure.
 
Just had a thought... OP, you didn't accidentally dilute 50/50 mix did you? Coolant with significantly more water than coolant will lower the boiling point. Granted it'd still have to be at least 212 degrees to boil... but worth asking.
 
This is a tough one. All the usual suspects have been addressed, and if it's not consuming any coolant it's unlikely that it's a head gasket issue.

I think the slipping timing belt is a possibility considering that everything else has been checked, but I'm with the OP that I'd be reluctant to tear into it without more evidence.

The problem really sounds like the fan isn't doing its job to me, even if it seems like it's working right. If it were the timing belt slipping on the pulley I would think it would overheat at speed as well as in traffic, but the fan would only cause issues at low speed where there's reduced airflow through the radiator.
 
SO the radiator looks like it is flowing with the cap off.
The hoses are not collapsing when engine is revved.

The coolant is definitely not diluted past 50/50, it is a proper mix.
Yes, :) I added the water wetter for good measure.

Thanks again for all your replies, I really appreciate the help!
I drove for over an hour last night on the highway with no overheating.
It seems pretty clear that this is only happening in traffic. Unfortunately, traffic is a big part of my life.
 
Update, I was stuck in some of the worst traffic yesterday. 90 degree heat and 3 hours of stop and go because the NJ Turnpike was closed (crazy accident).


I began to overheat 40 minutes in and cranked the heat. It was miserable being that hot out with the heat on, but I must say- the temp never got above normal with the heat on. I'm not sure if I'm reading too much into this, but it seems like I just need a little extra cooling.

Would it be insane to simply route the heat outside of the car for the time being and use the heat as an auxiliary cooler? I'm getting desperate.
 
the1998sr5 said:
Update, I was stuck in some of the worst traffic yesterday. 90 degree heat and 3 hours of stop and go because the NJ Turnpike was closed (crazy accident).


I began to overheat 40 minutes in and cranked the heat. It was miserable being that hot out with the heat on, but I must say- the temp never got above normal with the heat on. I'm not sure if I'm reading too much into this, but it seems like I just need a little extra cooling.

Would it be insane to simply route the heat outside of the car for the time being and use the heat as an auxiliary cooler? I'm getting desperate.
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I know you've checked it more than once, but this really sounds like the fan isn't working like it's supposed to. Is the fan shroud still on there, and in good shape? These trucks just don't need extra cooling capacity when everything is working properly. There HAS to be something wrong with yours somewhere.
 
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Don't give up given all you've tried. I feel its either the fan not pulling air as jeremyc74 said (could the blades be warped somehow?) and/or the heater control valve isn't allowing full flow. Have you checked those two out?

As stated the cooling system on these trucks is Very good, I can allow mine to sit idling in 100 degrees with the a/c on for over 2 hours (hood closed) with the engine water temp never climbing above 200. :cowboy:
 
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The fan shroud is there, and in good shape. The blades are in good shape as well. I broke one of the blades a year ago and replaced the plastic fan blades. I will say however, that driving with a broken fan was making the engine shake and I thought it was misfiring. I drove around for 3 months like that because I thought it was a misfire- and I was replacing plugs and wires at first, then the coil packs before I realized it was the missing fan blade causing this. Does anyone think driving with this imbalance may have messed something up? For full disclosure, I was only missing one blade and the engine never overheated while this was happening- or for 6 months after.

-I know there IS something wrong...I know these engines are well-cooled, that is why this is so frustrating. I want to fix it properly, but If I could get by with a band aide (extra electric fan, or leaving the heater on but rerouting it outside the cab for the summer) that would be better than the situation I have now.


Tell me more about this heater control valve? Where should I start in terms of checking this? How would this make the car overheat when the heat is off, but run normal with the heat on??
 
the1998sr5 said:
The fan shroud is there, and in good shape. The blades are in good shape as well. I broke one of the blades a year ago and replaced the plastic fan blades. I will say however, that driving with a broken fan was making the engine shake and I thought it was misfiring. I drove around for 3 months like that because I thought it was a misfire- and I was replacing plugs and wires at first, then the coil packs before I realized it was the missing fan blade causing this. Does anyone think driving with this imbalance may have messed something up? For full disclosure, I was only missing one blade and the engine never overheated while this was happening- or for 6 months after.

-I know there IS something wrong...I know these engines are well-cooled, that is why this is so frustrating. I want to fix it properly, but If I could get by with a band aide (extra electric fan, or leaving the heater on but rerouting it outside the cab for the summer) that would be better than the situation I have now.


Tell me more about this heater control valve? Where should I start in terms of checking this? How would this make the car overheat when the heat is off, but run normal with the heat on??
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did you replace the fan with an OEM?

I agree with the others, that it sounds like a fan or fan clutch issue.

is it possible the belt is routed incorrectly, causing the fan to spin the wrong direction?
 
the1998sr5 said:
The fan was OEM from Amazon:
Amazon.com: Genuine Toyota Parts 16361-62010 Radiator Fan Blade: Automotive


the fan is spinning in the right direction:)
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I suspect the fan clutch is bad, even though it's been replaced already. The reason I say this is that it takes so long for it to overheat it's the only thing that makes sense. Normally without the fan the engine will overheat in a matter of about 5 minutes of sitting still. I think your clutch is just not fully engaging, or is getting worse and worse as you drive, and that's why it's taking so long. The fact that the heater is enough to bring it back under control tells me it's simply an airflow issues, and the clutch is the only thing that fits the bill.

Oh, and just FYI, there are a LOT of counterfeit parts being sold as OEM these days. The stuff is coming out of China, and eBay and Amazon are two major outlets for it to get into the US. I work in automotive manufacturing and one of the companies I work with makes airbag sensors. They've gotten involved in cases where airbags failed to deploy, and the investigations revealed that the sensors had been replaced with what were supposed to be OEM parts that were actually rejects from one of their plants in China. These airbag lines produce a part in less than 3 seconds, and on a bad day they can generate thousands of scrap parts. The Chinese hate to throw anything away, so they slip them out the back door and sell them. The parts look perfect, and have all the OEM markings, but they don't work properly. Sad reality in todays world.
 
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