Boiling sound at radiator, radiator cap blowin off

**lanprat** · 08-01-2012, 07:52 PM

My car is blowing the radiator reservoir cap off. It seems to have a lot of pressure... Was thinking head or head gasket but it still runs great, no radiator fluid in oil, changed cap no difference.. Thermostat is good pulled it out yesterday, the car also likes to get nice and warm as this is happening, only happening when I get in it. Drive like a Sally and she doesn't overheat.. I know this is a pressurized system, but I pulled both radiator hoses off and ran the car with straight water going into the water pump, did the same with the car off and it had the same flow rate, could this be the water pump? Please help!!

**98maro** · 08-01-2012, 08:12 PM

could be thermostate, fans not working, or you need to replace the cap..
mine had the same issue a while ago, the problem was clogged hose, the one that goes to the reservoir, replaced that house, problem was gone

**lanprat** · 08-01-2012, 10:14 PM

Did your car overheat as well? And was it blowing radiator fluid out of the radiator reservoir cap as well?

**98maro** · 08-01-2012, 10:35 PM

yes the temp was always high, the antifreeze was coming out of the radiator cap, not the reservoir,
if its coming out of the reservoir, i would say is the termostate, you can also flush the cooling system.

**SuperSSguy** · 08-01-2012, 11:14 PM

Originally Posted by lanprat

My car is blowing the radiator reservoir cap off. It seems to have a lot of pressure... Was thinking head or head gasket but it still runs great, no radiator fluid in oil, changed cap no difference.. Thermostat is good pulled it out yesterday, the car also likes to get nice and warm as this is happening, only happening when I get in it. Drive like a Sally and she doesn't overheat.. I know this is a pressurized system, but I pulled both radiator hoses off and ran the car with straight water going into the water pump, did the same with the car off and it had the same flow rate, could this be the water pump? Please help!!

First check for leaks if your able to get a radiator pressure tester that does the radiator and has a cap tester do that this will put the system under pressure and see if youve got any leaks...If you dont have leaks - make sure your radiator is not plugged and is flowing properly- sometimes even a new thermostadt can be faulty-make sure its the correct temp range for your car and make sure you have it installed in the proper direction of flow-water pump impellars can go bad but unlikely- Now to the head gasket,your gasket can have a slight irregulariy-or the head itself can have micro-fissures (small cracks) so small that while not seeping anti-feeze into the oil CAN cause exhaust vapors to seep into the cooling system,this will cause high temperatures and boil-overs but the car will still run fine until it overheats...so when your just cruisin its ok but once under higher pressure the cooling system cant operate correctly and dissepate the heat generated by the exhaust gases.

**2002ssslp** · 08-02-2012, 07:41 AM

Do not over look collapsed hoses when you put pressure on them under WOT. You may also have a bad radiator, it may be cloged inside. Do you have an infrered temp gun, if so shoot the radiator and look for cold spots. If the hoses are more then 4 o 5 years old the replace them. Did you put the thermostat in hot water to see if it opened ? Waterpump impeller could also be the issue. Pull the pump ( better then blowing the engine )if the other ideas do not work. Good luck.

**lanprat** · 08-05-2012, 05:59 AM

After reading and trying different thing for weeks I finally gave in, took it to a good little shop that does nothing but "Hot Rods" and within hours it was done. What was it?? Turns out it still needed to be burped. I tried doing that several times. Must be a trick to it that I never read. Thanks everyone for responding nonetheless.

**SuperSSguy** · 08-05-2012, 04:29 PM

Originally Posted by lanprat

After reading and trying different thing for weeks I finally gave in, took it to a good little shop that does nothing but "Hot Rods" and within hours it was done. What was it?? Turns out it still needed to be burped. I tried doing that several times. Must be a trick to it that I never read. Thanks everyone for responding nonetheless.

OooPs!

I forgot my mechanics 101`s first rule...try the simplest thing first!!!! My bad..I should know better too! While not a certified mechanic(dont have the patience,more of a driver then mechanic) ive had a few years (20 yrs)of automotive experience running a service station (family business)..and over the years ive seen it all!....But i have to admit i screwed the pooch on that one...

..The ol burping.....yeah alot of air bubbles can be trapped in the block or radiator...even the smallest air pocket can cause a problem!! Im glad you solved your problem but it also brought me back to basics...Instead of going all crazy thinking cracked blocks,bad impellars,collapsed hoses,clogged radiators (which were all good guesses!!) I forgot the golden rule.."'Start with the simplest thing FIRST!"