Heater Cores Blowing Up

rconaway · Jul 31, 2007

I've been through 3 heater cores in a month on my GT. I added a bypass hose around it with T-connectors and that only worked for a week. Any idea on how the pressure can build up so high that the heater cores are leaking yet there is no other problem in the cooling system that I can find. Thermostats and radiator caps have been replaced and test perfect with a pressure test. Does anyone make a stronger heater core? I haven't had this problem in 70K miles and then all of a sudden it's an epidemic. The engine was rebuilt 10k miles ago but I'm not sure if this problem started occuring right after the rebuild or not.

chuck943 · Jul 31, 2007

http://www.4s.com/fourseasons/tech_tips/tech_tips_english/AB350_Electrolysis_02.pdf

Read this should help you with your problem.

rconaway · Jul 31, 2007

Will this cause failures within 2 weeks?

nyuk98gt · Jul 31, 2007

rconaway:

There is a flow restrictor in the outlet line of the heater. It is inside the tubing but you can see it. If it is missing, the heater will see full flow. It sees about the same pressure with the restrictor (since the restriction is on the outlet end) but the flow (fluid velocity) may be causing some vibration issue that is causing the heater to fail. Kind of 'out there' as far as explanations but a possibility.

The corrosion issue can be quick, depending on the chemistry of the coolant and the operating temperature and the quality of the metal in the heater (especially at the welds and bends [thinnest part of the tubes]).

HTH,

Chris

[EDIT] NO, the restrictor is in the INLET hose, not the outlet hose! [END OF EDIT]

forum155pl · Jul 31, 2007

you need that restrictor.. i had the same problem cept it was only 2 cores..

jivepepper · Aug 1, 2007

nyuk98gt said:
rconaway:

There is a flow restrictor in the outlet line of the heater. It is inside the tubing but you can see it. If it is missing, the heater will see full flow. It sees about the same pressure with the restrictor (since the restriction is on the outlet end) but the flow (fluid velocity) may be causing some vibration issue that is causing the heater to fail. Kind of 'out there' as far as explanations but a possibility.

The corrosion issue can be quick, depending on the chemistry of the coolant and the operating temperature and the quality of the metal in the heater (especially at the welds and bends [thinnest part of the tubes]).

HTH,

Chris

Ran without a restrictor for years no problem. Maybe you are pressuring the coolant system because of a small head gasket leak.

Muscleford · Aug 1, 2007

The flow restrictor needs to be in the inlet line of the heater at the intake end. That keeps the pressure out of the line to the heater. If it is in the outlet you let the pressure build in the core. If you put the restrictor at the heater end of the inlet you may burst the hose. Mine kept moving down the hose so I put an additional clamp at the inlet end around the flow restrictor to keep it in place.

rconaway · Aug 1, 2007

I have the restrictor in there and it's on the correct side but thank you for the suggestions.

steve_stang2003 · Aug 1, 2007

rconaway said:
I have the restrictor in there and it's on the correct side but thank you for the suggestions.

Had the exact same problem on a Chevy small block. Turned out to be a hidden restrictor in the molded hose that I refused to buy for $145.00. I went cheap and just put on standard heater hose.

I went through 3 cores, each of which lasted almost EXACTLY 30 days to the day before blowing. A GM parts guy clued me in.

Also on the same car I have had a small exaust leak into the coolant for as long as I remember. I had to drill a very small hole in the edge of the thermostat to allow the gas to pass on startup or it would buildup at the housing and the thermostat would not open.
I never fixed it because the car is currently approaching 500,000 miles and this has been with it since about 150,000 miles.
It's a 92 Caprice 350 and is still all original including the tranny.

Just some things to consider.. You also might want to check to make sure the restrictor didn't blow open. I haven't been in that area of my Stang yet so I'm not sure how it's set up.

Also check for electrolysis as well like the other people suggested.

Good luck

nyuk98gt · Aug 1, 2007

Muscleford said:
The flow restrictor needs to be in the inlet line of the heater at the intake end. That keeps the pressure out of the line to the heater. If it is in the outlet you let the pressure build in the core. If you put the restrictor at the heater end of the inlet you may burst the hose. Mine kept moving down the hose so I put an additional clamp at the inlet end around the flow restrictor to keep it in place.

Thanks, Muscleford! That makes much more sense than a restrictor on the outlet side.

Chris

rconaway · Aug 12, 2007

Thanks guys. I'll check the factory hose out and see if there is something different about either of these hoses.

Heater Cores Blowing Up

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