Did you "burp" the air from the coolant?

 

Check to insure that the radiator cap is on securely.

 

Purchase a hydrometer to check the boiling point of the coolant. Your mix could be faulty disallowing adequate cooling.

All of the above are potential candidates for warm coolant temperatures.

If your fan is noisy that would indicate the fan is 'on' more often and should not result in warmer coolant readings.

 

Cooling system was burped and the rad cap is secure. Also forgot to add that the throttle body was thoroughly cleaned. Coolant level hasn't dropped a hair in either the rad or the reservoir since I burped it the second time on Monday. Since then I've put about 500 miles on it.


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From my understanding of how the fan clutch works, when the coil reaches a high enough temp, it opens a valve allowing the fluid to flow to the outer fins, which using centrifugal force, pushes a friction plate attached to the outer housing against a clutch plate on the inner shaft (water pump side), thus engaging the fan. From what I've read, the whirring noise occurs when the fluid has not yet reached the outer fins which is why the sound occurs if you start driving before the engine is fully warmed up. Correction, the fluid itself creates the friction between the clutch plate and the outer housing. BorgWarner has a video on YouTube on how they operate. That's my take on it.


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I just realized that I still have the old fan clutch so I think I'll throw that back on and see if it makes a difference. It's recommended to replace the fan clutch anytime the water pump is replaced. That's the only reason I replaced it. Should have an update on it tomorrow.


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Maybe I am using a different definition of 'whirring'.

I just go by the fact that if it sounds like a plane is taking off then the fan is drawing a crap-ton of air in.

After the vehicle is up to normal operating temperature, shut off the vehicle to see how slowly or quickly the fan quits. Then once it's shut down, try to spin it to see if it spins free or if there is resistance.

I'm sure we mean the same thing just coming at it from a different direction. It sounds like you know how a fan work as well as anybody.

 

The water pumps are pretty lazy at low rpm in theae motors. What brand did you go with?

 

The sudden temp spike happened on the highway while cruising at a steady 2000 rpm on a flat road. This was the second water pump I've put in it. The first was about 2 years ago. I only replaced it this time because it had a slight leak from the gasket. Both were Duralast brand. It was a free replacement because of the lifetime warrantee so I figured, why not? I've never had any problems with their products. Autozone's great with that. Especially brake pads/shoes. Free replacement as long as they're not worn to the backing plate. Not sure how they make a profit with a policy like that but who am I to question something that saves me money lol.


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SUDDEN temp spikes kinda sounds like bad electrical connection in the temp sending unit to gauge circuit. Could u have bumped/loosened something in that circuit when doing the other mechanical repairs?

 

I'd say replace the thermostat with a Stant piece; 180*

 

I've been looking for a 180 degree thermostat but have been unsuccessful in finding one. I've read that many people have bought them only to find out it's a 190 in a box for a 180. Someone even called stant and was told that the company that manufactures their products no longer makes the 180 for our trucks since GM switched over to the 190.

Anyway, I replaced the fan clutch with the old one. Temps are stable, gauge is staying where it should be, and the whirring noise is gone. So far it looks like I bought a defective fan clutch. I'll be keeping a close eye on it with the dashcommand app for a few days just to be sure. If anyone knows where to get a true 180 degree thermostat, please let me know.


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I'm running a Stant #14077 170F in my V8. I don't know if V8 stats will work/fit in I4/I5 motor.

This time of year (3 digit ambients) the ScanGauge floats at 185F-190F. Dash gauge shows 2 dots below 1/2 mark. 5 mos from now ScanGage will float at 175F-180F and dash gauge will still be 2 dots below 1/2 mark.

 

If you want a lower temp statfot the i4. I5 you have to make it yourself. I checked 3-4 years ago and called a few of the top manufactures. All of them backed out of making a custom stat.

 

Search on this one, I think it's still a 180 - Stant 48718 XACTStat

[ame]http://www.amazon.com/Stant-48718-XACTStat-Fahrenheit-Thermostat/dp/B001FI2GXU[/ame]

 

Search on this one, I think it's still a 180 - Stant 48718 XACTStat



http://www.amazon.com/Stant-48718-XACTStat-Fahrenheit-Thermostat/dp/B001FI2GXU

Good pricing but the reviews show that it's the newer, higher temp replacement.

I read a post somewhere about modifying the stat by taking it apart and adding a thin aluminum washer to make it start opening at a lower temp but have been unable to find it again. I'll keep looking for it and post a link if I find it again.

With the low pricing on eBay and Amazon, it be worth playing around with to get operating temps back to where our engines were initially designed/calibrated to run at. Even if for nothing other than peace of mind.


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Your truck should operate absolutely fine with the replacement thermostat temperature with no concern of damage.

 

It does run fine but ran cooler with the original thermostat. In my case, I'd like it to open sooner for towing purposes. Temps are higher than I'm comfortable with before I get on the highway. I noticed a considerable change when towing after I had replaced it.

Here's my reasoning, with the original thermostat, towing a boat weighing almost 2500 lbs, ambient temp around 90 degrees, the gauge would show almost halfway between 1/2 and 3/4 at the highest point. With the replacement, on a day with similar ambient temps, the gauge would go up to and sometimes a tick higher than the 3/4 mark. At that mark, my scanner shows a coolant temp of 219 degrees. From what I've read in other posts from more knowledgable people than I, any temp from 225 on up is bad news for our motors.

I'm not sure why there was a difference between the two thermostats at that high of a temperature as they should both be fully open at that point but it was consistent. I'd just be more comfortable with a wider gap between my readings and the 225 mark.

Anyway, I found the link http://www.355nation.net/forum/showthread.php?t=55130


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219 is a safe temperature for our trucks and 225 is not the danger point. For our trucks they run better the hotter they are (to a certain extent). The real danger zone for these trucks is 250, its pretty hard to get it to 250 lol. On hot days I've seen my temperatures reach 220. Do not go by what the needle gauge says, that doesn't tell you what your actual temperature is. Always go by a scangauge or something digital. Anyways, take readings of your temperatures with something exact during idle, city driving, highway driving...then turn around and take the same readings while hauling something. Remember, just because your needle says your coolant is hot doesn't always mean it is. Those things are known to be wrong.

 

Somebody once wrote an interesting piece about the cooling system. One of the members here. I think it could have been DJB.

He wrote something like "The thermostat only control the minimum operating temperature". Essentially meaning that once it's hot, it's going to stay hot. When the thermostat is fully open, it's then useless for keeping engine cool. Therefore, if you are above 185 degree normally then the thermostat is open anyway, making it no different than the stat you have installed. Does it warm up a tad more relatively, of course. But once hot, it's hot and the thermostat will do nothing to cool it back down. But it will not keep you truck cooler while towing.

Get a hydrometer to check the specific gravity of the coolant to determine your boil over temperature. Change the radiator cap if you haven't already (I think you said you have).

My truck will hit 215 in high ambient, in traffic with A/C. I disagreed with that when I purchased the truck a couple years ago. I purchased an Ultragauge only because I wanted to know my water temperature. I later learned how common/typical it is to run at this temperature.

I normally hit around 196 under normal summer conditions. 90+ ambient. A/C maybe on. Running around town. 188 when it's not that hot outdoors.

 

Just don't make it run to cool and your good. 180-185 is perfect year round .

 

2006 Service Manual (Isuzu, I350, 4wd).

Thermostat Diagnosis:

Thermostat Test Procedure Using Tempilsticks

The coolant thermostat can be tested using a temperature (tempil) stick. The temperature stick is a pencil like device. It has a wax material containing certain chemicals which melt at a given temperature. Temperature sticks can be used to determine a thermostat's operating range, by rubbing 87°C (188°F) and 97°C (206°F) sticks on the thermostat housing (4).

Tools Required
J 24731 Tempilstick

Use a tempilstick in order to find the opening and the closing temperatures of the coolant thermostat.
• J 24731-188 tempilstick melts at 87°C (188°F). The thermostat should begin to open at 90°C (194°F).

• J 24731-206 tempilstick melts at 97°C (206°F). The thermostat should be fully open at 107°C (225°F).

Replace the coolant thermostat if it does not operate properly between this temperature range. Refer to Engine Coolant Thermostat Replacement .

 

A properly functioning t-stat does one thing and one thing only.....determine minimum coolant temp. The rest of the cooling system components, their condition and driving conditions determine maximum coolant temp.

 

that's what i had initially thought, but the changes that i had noticed had me questioning at what temp the higher thermostat is fully open and maybe it doesn't reach that point under normal driving conditions, making it seem more drastic when it does. basically overcomplicating things.

The more i think about it the more likely it seems that scale buildup may have caused the difference that i noticed and that i'm just blaming the thermostat because the temps didn't get so high on the original. i never factored in the age of the truck until now.

Anyway, my initial problem with the spiking temps and whirring sound were in fact caused by the defective clutch fan so i'll be returning that tomorrow. I haven't had any issues since re-installing the original so i'll just leave it in. Temps stay steady at 199 on the hwy and peak at 203 driving local or sitting at idle even with a/c on.

Thank you everyone for your input.


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Wow I was right. It WAS you that I remembered that quote from. LOL

 

I hope others remember it too. LOL

 

ahhhh, the unsuspecting clutch fan. Well at least you found the issue.

 

Efan ftw