[thunderstruck507]

My car loves to blow out a heater core, usually almost every year. I am really getting sick of it. I've tried new ones and repaired ones and there doesn't seem to be a difference. They nearly always go out in late summer/early fall.

The radiator cap is a 16lbs that was on the 3 core radiator when I bought it about 6 years ago. The only thing I can think of is for some reason the radiator will not overflow in or pull from the coolant tank...is this the source of the problem? Excessive pressure or something?

Any other ideas?

 

[Motorhead62]

My El Camino has the same problem bro. So what gives?

 

[Mike]

Test the cap with a pressure tester to see what it opens at.
If that checks out ,w ith a pressure tester attached to the filler neck ,bring it up to op temp and see what it shows for pressure.
Try it at various RPM's that you usually run in to see if it goes up.
It's probably the cap as there's been some out that open above 24#.

 

[Schurkey]

Oldsmobile engines used a restricted fitting in the hot water outlet from the intake manifold to the heater core.

Failure to re-install the restrictor will result in split-open heater cores. The dynamic pressure (not rad cap pressure) of the coolant flow is just too much on the Olds engines. The size of the orifice is larger than 7/32" but smaller than 1/4". I haven't noticed anything like that on Chevy engines--but--it's not like I see a lot of those fittings lately; and I didn't know to look for a restriction years ago.

http://72.22.90.30/phpBB2/viewtopic...der=asc&highlight=heater+restriction&start=15

http://72.22.90.30/phpBB2/viewtopic.php?t=43160&highlight=heater+restriction

Aside from that--is the body nicely grounded so there's no current flowing in the cooling system? The anti-freeze isn't fifteen years old and doesn't look like hot chocolate?

 

[ls5-70ss]

When you say blowing, is the heater core actually swelled out or just busting? If the core is swelled out it is a pressure problem, if leaking it is a vibration issue or damage issue. If it is swelled, you might want to do a combustion gas test on the coooling system. Learned after three cores in my 69 Camaro to check the core before installing!! Let a radiator shop check it out before you install it!! If the heater core had a clip or bracket holding it to the heater box, make sure they are there. Check to see if it had any foam or insulators around the core. Thomas

 

[Chris R]

This sounds like something similiar to holding your finger over a garden hose to get a stronger spray. I would check all your hoses and fittings and make sure nothing has collapsed or even kinked. Could be something plugged in there causing the flow to build up.

 

[thunderstruck507]

The cores are busting. Usually a pinhole.

As far as having them tested at least 2 of them have been ones I've taken to the radiator shop for repair. The rest have been new.

I'll see where this one is leaking when I pull it and test the cap out.

It has been doing this with both my old 350 and the LS1 btw.

 

[thunderstruck507]

Put on a 13# cap with the last heater core (last Oct-Nov).

Smelled coolant and got a couple drips again Saturday.

I will be installing some kind of restrictor this time. This is ridiculous.

 

[Dan Dietrich]

My 76 c10 454 gone through the original + 2 new ones from NAPA?
Going to bypass until I can figure out what is going on. Just had the
heads rebuilt, new radiator and water pump. #16 cap on the radiator,
it is the same as the one on my suburban and has the same amount
of resistance on the spring.

DD

 

[davewho1]

 

[hydro462]

Check the bypass port at the water pump and change cap.. I use a 4-5 lb cap..

 

[lucifershammer]

Do you have the hoses on right? The 3/4" hose should go to the water pump, the 5/8" hose should go to the intake manifold (for a stock flowing water pump.)

If you have them backwards, you can build up extra pressure in the heater core.