Truck temperature fluctuates

[JetMech]

(04-15-2013 07:56 PM)That Guy Wrote:  my money is on air in the system. Again, look for a bleeder somewhere around the t-stat. Looks just like the bleeders on your brakes. get it up to temp then CAREFULLY bleed the system through the bleeder. use a tube or hose if you can to direct the hot stuff away. If not, put a folded rag over it and use a long wrench so you don't burn yourself. Hot coolant WILL come out and if air comes out, it will be even hotter. Hot enough to ruin your weekend anyway.

Good luck and the offer to help still stands.

- Justin

Thanks dude. I will look for bleeder and also replace rad cap. More to follow.

[The Doctor]

I think you just need more duct tape. Always works for me.

[the falcon]

Check your fan clutch

[Rev. That Guy]

at cruising speed the fan wouldnt do anything... it cant move the same amount of air.

The fan would only make itself apparent if the problem occurred while stopped.

- Justin

[JetMech]

So I put a new cap on it with a vent tab. I checked the coolant level and it was completely full. After driving it twice and getting up to operating temp both time, I did burb it and did get some air that came out through the vent tab on the new cap. I will romp on it during my commute back home today.

[JetMech]

So on my way home, I romped on I and the needle didn't move as much as it did yesterday. After stopping at the store I did vent the air out again. Each time I have gotten air out of the system. So I will let you know what happens on my drive to Cali. I think That Guy might have been on to something.

[Rev. That Guy]

this aint my first rodeo...

Glad I could help out. Some systems are more sensitive than others - you seem to have one of those sensitive ones. keep it up and keep us posted.

- Justin

[JetMech]

So on my way out to SoCal, truck loaded up with bike, track equipment, and la familia with suitcase for each of us, going up Mt. Pass, I floored it to accelerate from 55 to about 85, and the temp went to the half way point and never went higher.

So I discovered that with this new stat and radiator, my truck is actually running a few degrees below operating temp. Normal operating temp for my truck is 203. Since I have owned the truck, the needle has always stayed right at the middle mark. With my old thermostat, whenever I romped, on it it would go about 3-4 needles width past normal operating temp which is the middle mark on my gauge which is why I replaced the stat. So I continue to burp the system of air any time I stop the truck and I still continue to get just a tad of air everytime. I will assume that this should eventually stop and I hope that my temp gauge will start to normalize a bit. Lets see what happens tomorrow.

[Rev. That Guy]

if you are down to just a tiny bit of air each time, stop bleeding/burping it. This means you have basically gotten all you need to worry about, out. There will always be some vapor trapped in there that the coolant mixture has water in it. When it gets hot, it will build some pressure and create a little vapor, but will turn back to liquid when cool.

You likely are running a tad cooler now in general. most aftermarket (even "OEM" aftermarket) radiators are generally 30-50% thicker cores. Some are even bigger than that. This is relatively normal for reasons im not sure of. that being said, it can cause some funny things to happen. For the most part, your truck should run a tad cooler overall. What you might see though is small fluctuations of temp from just below normal to normal. This is due to the t-stat and the additional cooling. The t-stat is there for a few reasons but mainly is to allow the engine to reach operating temp. When you are on the highway, often your t-stat may not be open at all. If your radiator is cooling effectively or too effectively, your t-stat will stay closed to heat up the coolant in the engine a bit more, then when it opens, you get a rush of warm coolant, thus displaying the raise in temp, and then the t-stat closes again and the cycle repeats.

This fluctuation should not be too sudden or go away too quickly. It should be relatively gradual and if it is at or below normal, dont worry about it.

On my magna, before i deep cleaned the cooling system, the bike would run warm, but the temp stayed pretty steady. After running CLR and water for a few days and flushing it, the radiator looked brand new inside and I installed a new t-stat. After all that, the bike hovers around 185 on the highway and you can actually see the cycles of the t-stat because the temp will shoot to 191 (exactly, never over while riding highway) and then slowly work its way back down to 185 again. This is because the t-stat is not a good match for the now properly working radiator (went with a lower temp t-stat). Only sitting at lights for a long time have I even hit above 200 and even then only a few degrees. Im ok with this though once the temps around here start climbing. Cooler is better for me.

What Im getting at is that it seems that things are working out, and your truck is not getting hot. Even though you are having some light fluctuations below normal temp, I dont see anything to worry about. Be worried if it starts fluctuating to the hot side.

I say your probably good. Burping it seems to have helped in evening it all out. Run 'er!

- Justin

[JetMech]

Thanks for the help dude. Totally makes sense now.