claus

I used one of two products available at the local AutoZone. They had Prestone engine flush and a product with the word "blue" in it. I chose the former. Not sure if it is acid based or not.

The radiator was replaced with a new one last year, and with the engine flush I was hoping to dislodge any buildup in the engine that could be the cause of the rising temps under just a light load.

claus

Think Thommo might be on to something about the glycol coolant vs. plain water.

Yesterday I filled the system with red Toyota specific radiator coolant, and on the normal trip I have been using to measure the difference in temps it showed an increase when I drove it today.
Several times the temp went to 194F during the climb up some moderate hills.

I also checked the radiator hoses when I arrived back home, and the top hose was hard, so no air trapped there.
I added some coolant to the expansion tank because it was at the low level. Another indication that the the air is exiting the system.

Original problem still exists:
With a 181F thermostat the temp climbs consistently to above 190F under what I would call light to moderate load going uphill.

The attempted solutions:
Installed new radiator, installed tranny cooler, installed new water pump and thermostat (part of the deal when I had the timing belt replaced), switched to a lower temp thermostat (181 from 188), ran Prestone coolant system flush in the system for 3 hours.

Switching O/D off does help a bit but doesn't "fix" the problem.

Question:
Could the temp problem be caused by the timing belt being off by one tooth on either or both cams.?
The engine knock disappeared after the belt was replaced, so...???

I grasping at a solution here, but I'm running out of options, and as I said in the original post, I think I may have a flow problem, which leaves the water pump.

I'll keep digging and post my findings.

Thommo Thompson

thats right, if its full it should be quite hard. its very difficult to propperly bleed a cooling system, but it should be ok with a bit of air stuck. id say if u can clamp the top hose together, theres too much air.

claus

The upper hose was pretty hard when I parked the truck after my drive today, so there is probably enough water flow.

We have some pretty steep and tall mountain roads and I'll try one of them in the next week or so, and see how high the temp will actually go without me trying to baby it.
If I reach 215+ I'll pull off the road and let it cool down.

Thommo Thompson

dont forget, air can compress, so after a certain point, it will compress to take up next to no space, so long as pressure is constantly being applied to it. so that means, u can have air in the system, and still get a solid top hose when hot. the more correct way to test it is when cold. a completely full system, will be solid and uncompressible when cold.
i have a little 4k motor which requires revving and holding those revs to 1200 rpm with the radiator cap open, (no thermostat installed), which pushes the air pockets forward to the radiator , and then while all the air is in the radiator top tank and visiable as a low level, i then fill the radiator, all while the revs are kept at 1200. if i were to rev it, and then let it back to idle, the air just flows straight back into the head. So the void muat be filled with water while it is being forced i to the toptank by the high flow wall of water being pushed through by the revving engine.
You will not find one mechanic who is experienced enough to be capable of bleeding all air out of a cooling system.
You have only succeeded, when the top hose can no longer be compressed.

claus

I think the expansion tank will aid in removing the air in the system, because when pressure is applied by revving high as I do when crossing the mountains and hills (2000-3000 rpm's), the air is expelled from the radiator to the tank, and when it cools down and create a vacuum, liquid is sucked back into the radiator from the tank.

In any case I will monitor the expansion tank and fill it with coolant as needed.

Thommo Thompson

U don't have an expansion tank, u have an overflow tank. Very different beasts.
and an overflow tank wont help remove air at all. An expansion tank would, but not an overflow tank.
with a fully closed system with a pressure relief valve, it is up to the person filling the system to burp it completely. It's physically impossible for the system to do it itself.

Expansion tank - sits at highest point and incorporates the filler cap. And contains a few cm of room for air (stupid system and requires 50/50 coolant water mix)
overflow tank - sits below the radiator and collects overflow and supplies it back to radiator on cooldown.
The overflow system doesn't actually help remove air. It's still a better system, as u can use a 70/30 (water/glycol) mix safely because it is deaigned to be completely full with no compressible air, meaning more water can be present due to higher pressures being sustained within the system than an expansion tank type System.

ZUK

iTrader: (1)

Hi Claus-
You don't have any problems there. The SG2 lets you see instantaneous temp changes unlike the factory gauge which is a joke and stays in the same spot from 160 degrees to 220 degrees. The weep hole on the thermostat might not pointed in the preferred direction and that can cause higher temps but it does not qualify as a problem.My 01 Taco 3.4L with auto sees 197(scangauge2) on the highway.....around town, it might it creep up to 198 199 200. It's the nature of the beast. I have a new radiator and new thermostat....might have the weep hole turned around but not 100% sure as my thermostat is in the LOWER hose area and it was installed in the 6 o'clock position. Scangauges are wonderful


Here's mine on the highway with the cruise ON and a normal 197. Note the tranny temps are a freezing 131 degrees That's because I have a well working external tranny cooler(bypassed the Radiator).
I strongly recommend since you have a 2000 Runner that you at the very least replace Radiator with a new one....and bypass it to eliminate any chance of the 4Runner Pink Milkshake.

Thommo Thompson

That's a damn good post. Haha

claus

Claus here...

Been a long while and due to my Yota having the aforementioned over heating problem, I used it less over the summer months.
Problem was still there all summer, but running without OD allowed me to at least use it for quick trips to the local Lowes for supplies.

That said I have managed to solve my problem, and it was the thermostat. The repair shop that replaced my timing belt (water pump and thermostat) even put in a lower temp thermostat after I complained about the severe over heating issue. As I mentioned before here, the shop guys didn't think that high 190's was anything to be concerned about, but that I couldn't climb hills without putting it into 2nd, showed that there was in fact a problem.

I decided to remove the thermostat completely and run it like that to see if the problem persisted, and it didn't. Even o the longest of hills (5+ miles) the temp didn't go above 175, and cooled down to below 160 on the run down the other side.
I sprang for an OEM thermostat (didn't know that wasn't what the shop installed), and when it got here I replaced it. I see now why it is called a high flow thermostat. These two didn't look anything alike! (see photo, the OEM is on the right)

Installed it and my temp is now consistently at 188-190, with the occasional "jump" to 192.

Thank you to all who helped me here, I greatly appreciate it!


Claus


PS. I also replaced my antenna, which had decided to spit itself out on top of my hood. A $140 investment for an OEM antenna (nothing else will work), and several cuts on my right hand from fishing the cable through the innards of the dash board, and I now have tunes again!

old87yota

Thanks for posting the fix!

Now you are good to go!