I can take my radiator cap off right after a 30 min trip?!?

[crsevns90]

Drove for about a 30 minute trip today after changing my coolant and after coming back home I touched the top of my radiator cap and it is barely warm. So I go ahead and loosen it a bit and notice that it is not spraying all over like most cars would do. So I take the cap all the way off and look down into the radiator and see that the coolant is still full. (I am doing this while the truck is running btw) Top radiator hose is hot as it should be, and so is the bottom. Temperature guage is right in the middle also. Is this normal or whats the deal?

 

[crsevns90]

Also, the coolant in the reservoir tank doesent move. It stays at the "full cold" mark when the engine is either warm or cold. Like I said the temp guage reads right in the middle, but something doesent seem right to me. Help!

 

[Wicked_Sludge]

id start by replacing the radiator cap if it wasnt done already (they are cheap).

still, with a bad cap i would expect to find a low radiator or over-full over flow tank after a long drive....

 

[crsevns90]

still, with a bad cap i would expect to find a low radiator or over-full over flow tank after a long drive....

Thats what I thought. I cant believe that I can take the cap off of a completely warm engine and not have anything spray anywhere, yet the guage is right in the middle.

 

[Wicked_Sludge]

the reason it doesnt spray all over is because the system isnt holding pressure for one reason or another....we just have to find the leak.

 

[crsevns90]

Alright, there is no water in the oil, and it is not a headgasket as there is no white smoke out the tailpipe, and with the cap off there is no air bubbling of the coolant. So could it be something as simple as a bad cap? What else could I look for?

 

[funkingonutz]

do a compression test(kit is cheap from NAPA) pump it up to 16lbs and go hunting for the leak

 

[Wicked_Sludge]

it could (and probably is) be as simple as a bad cap.

if a new cap doesnt fix it, have the system pressure tested and see where the pressure is going.

 

[chazzone]

While I'd probably replace the cap, just because, do you think that there may be a chance that you have an air bubble? Maybe in the heater core or lines?

Run the heater on full in the defrost position, and make sure you're getting HOT air.

-zz

 

[crsevns90]

Heater blows hot air. I got a cooling system pressure checker and hooked it up, pumped it to 16 lbs. and waited for about 20 minuntes. The guage never budged off of 16 and there were no leaks anywhere. Went out and bought a new cap installed it and went for a little drive. Same results. Im stumped.... something isnt right.

 

[Wicked_Sludge]

you got me then too. the only things that can cause a system not to build pressure is a leak, or not enough heat. you say the heater blows hot and the temp guage indicates normal temp., so it would seem the trucks warming up properly...and if theres no leaks then i dont know

sure you got the cap on all the way (second click)?

 

[crsevns90]

you got me then too. the only things that can cause a system not to build pressure is a leak, or not enough heat. you say the heater blows hot and the temp guage indicates normal temp., so it would seem the trucks warming up properly...and if theres no leaks then i dont know

sure you got the cap on all the way (second click)?

Yep, the cap is on all the way. I did notice something weird btw..... half of the radiator is hotter than the other half. The hotter side is the side of the upper radiator hose.... I cant hold my hand on that side for too long. The cap side I can hold my hand on it forever. This indicate anything?

 

[Wicked_Sludge]

hmm, hot and cold spots can indicate a plugged radiator or lack of flow (water pump)...but in either case the system should still build pressure from the heating of the coolant in the block...and either case would also cause overheating problems.

how many miles on your water pump?

 

[crsevns90]

55,000 original miles on the truck and waterpump.

 

[thegoat4]

If your radiator cap is bad you probably won't overflow the surge tank unless you get it absurdly hot. What the cap pressure guards against is localized cavitation around the water pump impellers, which you won't be able to see. If it goes on long enough you'll get a water pump failure as the cavitation eats up the blades. You may also get pitting within the block around the cylinders which could eventually lead to an internal water leak.

If the rest of the system holds pressure, but you notice no pressure buildup as you heat up the engine, replace the cap. Keep in mind that when you refill the system there will always be some air trapped. It will take a few heating and cooling cycles to get the last of the air out from under the radiator's cap. Until that air is gone the cap won't really feel as hot as you'd expect.