SmokenRam

Guys i'm pulling my hair out. I've been having this problem with my coolant overflow tank filling up too much and coming out the top. Some say it could be head gasket, my guy that dose most my engine work says it isn't. I change the thermastat about week ago and have been driving it, no probs at all. yesterday check the coolant in the over flow tank and it was at the right level, but the rad level was about an 1 1/2inch from top. so i filled it up. Then drove it and same thing, filled the overflow up and came out the top. I begaing to think i might just have too much coolant in it. When i shut it off and let it sit over night, and check it the next day, should the rad level be to the very top?? Help me out guys, I'm going CRAZY!! Thanks Chris

74dart

May be the spring in the rad cap is too lose causing it to overflow at to low a pressure.

MDMIKE

I second what 74Dart said. Don't overlook the cap as a culprit too. I had a very similar situation to yours just recently and the cap was one of the problems (JUNK NAPA thermostat was the other ). You might also have some junk on the rubber seal on the cap. Good luck.

MIke

John Faughn

It could be that your filling up the rad. too much , it should be not at the top , there should be some air space , so let the rad. run that 1 1/2" and watch the over flow , if the eng. is cold it should at the lower level and when warm at the upper mark on the overflow tank .
then check the rad. maybe once a week see if the rad. is still staying at the same level when cold.

SmokenRam

Why is that, I have left it at that 1inch below full in the rad, and its fine then. No over filling the tank, and its does get hot. should i just leave it like that and run it?? I heard a few people say that also, that the rad is not filled all the way to the top. Also i replaced the cap when i did the thermastat also. I think it just might be too full. I don't know??? Chris

John Faughn

The rad. needs some room for the water to expand , they didn't always have the res./expansion tank , yrs. ago .
but the still seem to need airspace even though they have the res.
You said it was getting hot , how hot on the gauge ?
If it is getting too hot then look for flow from the pump , then it could be a combustion leak into the cooling system ,
but check out the easy cheap stuff 1st.
Try running without stat. , could be a bad one , after getting out put in a pan and heat up with temp. gauge in to check .

Haulin_in_Dixie

Do put a new cap on it, then check the overflow tube to the tank for leaks. All that being good and if the radiator will not keep water in it you have air getting into the system, normally from a compression leak.

The way the system works.... As the engine heats up the overflow goes into the overflow thank. As the engine cools it pulls the coolant into the radiator keeping it full. There would be no air space in the radiator of a properly working system. The radiator cap had the rated per pound blow off as the engine heats up, but has just a check valve to let it pull back in.

Now realize this, if the slight vacuum of the system as it cools is not sufficient to pull the fluid back in, there is a leak. A compression leak can do it, a water pump can do it, actually any leak that will prevent the vacuum from pulling the fluid back in will do it.

To check for a compression leak on a 24 valve, do this. Pull the fan belt off the engine, pull the thermostat housing off the head along with the thermostat. Make sure the engine is filled level with the housing with water. Now start the engine, if there are bubbles coming up in the water you have a compression leak. You can do that test in a half hour.

On a 12 valve it is harder because of the horozontal thermostat mounting.

SmokenRam

Yes i replaced the cap also. It's not getting hot now that i changed the thermastat. Its working properly, It's dosen't go over 200.

So if this is the case, not pulling the antifreeze back into the rad, then how do i find where the leak is coming from??

Haulin_in_Dixie

Ok it is a 12v. You can get the system pressure tested. No leaks but a dropping pressure indicates a compression leak, but sometimes that is inconclusive because of the high pressure of the diesel. You can pull the thermostat and reinstall the elbow so that y ou have a place to check for leaks like it discribed in the thread. Pull the belt, start it up with the water full to the top of the elbow or hose and see if bubbles are coming out. That will tell yo right now.

SmokenRam

OK, heres what i did tonight. Drained the overflow down just right below the add mark. I then filled the rad up full. I did all of this cold. I then drove it around for about20-25min, good and warmed up. Pulled er back in the shop, look in the overflow while running, the level was in the same spot. I shut er down and and the level in the overflow did not move. The level did not move from when it was cold t'll it was warm. I thought when warm it was suppost to suck some out of over flow. I'm going to check it in the moring and see if it changes durring cool down. This darn thing is freaking me out!!!

Haulin_in_Dixie

It is near impossible to completely fill the raditor. When it warms up the first time it will only push the air out of it and when the system cools down it should pull the fluid out of the overflow to satisfy the amount pushed out when getting hot. Usually takes two or three cycles to purge all the air out of the radiator and start transferring fluid in and out.

SmokenRam

Oh OK, I'll do a few warm up's, and cool down's tonight, see what happens???

Geico266

Smoken, just relax. Your truck is not a gasser. It only heats up hot under a load. You can drive around and get it to operating temp, and tox something and really change everything. The outside air makes a difference also, in the cooling.

Put a new cap on it, check the over fill hose and connections and leave it alone.

SmokenRam

It has a new cap.

Why couldn't i start it when cold and check for bubbles looking in top of rad. with theramstat still in. If there's a compression leak, It should still bubble, Right???Chris

John Faughn

One or two posts ago you mentioned sucking out of the res./overflow when warm , its the other way around , heat expands & cold contracts , so when it gets to opp. temp. it expands into res. and when it cools off it sucks back into rad.
There should be 2 marks on the res. , full & add , it may be at the add mark in the morrning and full mark at opp. temp.
Your mention of air bubbles , you may not always see bubbles , sometimes the heat will open a hole and some times close a hole .
So check both hot and cold .