I noticed my truck had a few drops of coolant under it, and it was all over the axle and inner fender, on the passager side. So at first my gut drop, and i thought oh crap, the dreadfull head gasket. So I grab a flashlight and start looking, It was all on the passager side, but the block didn't have any on it, it was dry, and the oil looked perfect. so i don't think its that. it looked like it was all over the coolant over flow tank and blew back from there, all over the air box and stuff. And the over flow tank was full. So then i started it and let it run for awhile. When i poped off the over flow tank cap and looked in it, it was kinda bubbling. I thought its only suppost to shoot coolant in there if it over heats?? So could this mean my radiator cap could be bad and letting coolant fill my over flow tank and blowing it out the top??? Any help or suggestions would be great, Thanks Chris

 

The overflow is for just that , when you go in the morrning the coolant heats up and expands to the over flow tank , then when you park it and it cools off it contracts and suck out of the overflow tank , thats why theres to marks , for level hot & cold , but get ahold of a pressure tester and pump up the system and watch for leak , it could be a pin hole leak that only sprays out when the system is warm and opperating , theres also a heat exchanger on the rt. ft. of eng. that can leak , the bubbles in the overflow tank maybe just the fluid moving back & forth , but comfirm with pressure test , eng. warm and look in tank and all around to confirm ,then do the work that you need.

 

Well heres another thing i noticed, It didn't start doing this untill this week when i put on my new 40in Ground Hawg tires, They are a pretty big tire and are NOT balaced, I'm thinking of putting some ballancing sand in them. Anyway this thing ride ROUGH, I mean it's ROUGH! It shakes like crazy going down the road, and its a steady shake, Feels like your running over a strait strip of speed bumps. So what i was thinking is, for some reason its filling up that overflow tank too much. There's a "elbo" at the top of the tank that is just a open hole. I guss for if it would overheat then it would come out there. It fills that tank up about 2in from the bottom of that hole, If that truck is going down the road bouncing that much, Mybe it's sloching that coolant out that hole. Kinda hard to belive it would do that, But its a posibilty????

 

If I got what your saying rite , it couldn't happen , the raidaitor cap shouldn't let it slosh in & out , its kinda like a spring loaded valve , when theres pressure[warmed up ] it over comes the spring and goes into the res. , and when it cools the rad. develops a vacume and sucks out of the res.
Next time you look at the rad. cap take a look it has 2 rubber seals , 1 at the base of the cap and 1 the other side of the spring , thats the one that lets coolant to & from the res.
I would still pressure test to make sure that you have a problum or not .

 

I had kinda the same thing going on with mine for some time, particularly after giving it a bit of a hard run. Up to 30 lbs of boost up a hill I would end up with antifreeze under the engine after I stopped and under the inner fender well. I too thought it was my poor rad cap which wasn't holding any pressure and overflowing the tank. I replaced that and it still did it. I couldn't see any headgasket leak easily but it was there and that is what my problem was. Take a close look at your block and if there are any whitish colored stains running down the block you have a leaking headgasket.

 

Start with replacing the pressure (radiator) cap.

If that doesn't fix the problem it points to a head gasket. They don't have to leak externally so a clean block is not a good sign.

Follow John F's advice and try a pressure check.

 

the bubbles you see is probably the head gasket leaking compression int the coolant passages, they sometimes will do this with no visible evidence in the oil or on the block.....do the pressure test if the needle rises quickly it's a internal leak

 

I mean on the top side of the res tank. Theres a eblow pointing down and is open for fluid to come out, look on your trucks, you'll see what i mean. Before i drove it tonight, i made sure the rad was full and the res tank was proper level, but after i drive it, the res tank fills up about an inch from the top, and the rad level is down, so why is it filling up the res tank so much.

If they don't leak externally then where else can it go?? Oil looks perfect.So if its filling the res tank too much, then this could be the cap?

Another question, I've noticed this for a while, It seems like the water temp will go up to about 210 or so, then the thermostate opens and it jump down to 180. 210 is a little to high of a temp to rech before the thermostate opens, isn't it?? I replaced it about two years ago and it was suppost to be a 190, Could cause anything??? Thanks Chris

 

I understand what your saying there, but would it show it bubbling in the rad or res tank, or both?? Probly do a pressure test tommorow, Never done one before so just kinda courious how they work??

 

Pressure test is using a airpump that has a end that fits on the rad. insteed of the cap , you pump it up to about 15-20lbs , and then go around the eng. and anything that has coolant passing through it [ maybe with a flashlite ] and lok for leaks , if it is the worstcase then what you would be looking for is a slow loss of pressure on the gauge , you can'nt look for bubbles in the res. becouse now with the tester conected to the rad. its not connected to the res. anymore.