Chasing a heater problem

[BikeIdiot]

I have a heater core that is getting clogged with rubber material about the size of sand. Thus the heat only blows hot if I back flush the core to clean it out. After this, the heat only blows hot at 2,500 rpm and higher. Then within 50 miles of highway driving, the core is plugged again and cools off.

I have, over the past year, changed the heater core, radiator, thermostat, replaced all heater hoses, and bypassed the rear heater core. The block was flushed. I now understand this may have been a mistake. Running new red coolant.

Any ideas what else could be creating rubber to be created in my cooling system?

 

[pluton]

Radiator hoses could be degenerating on the inside? Oil cooler hoses?

 

[Dieselchessy]

And nothing you removed was degraded on the inside?

AFAIK

Rubber = oil cooler lines, radiator hoses, heater hoses, IAC hoses, RTV sealant, thermostat seal.

Plastic = radiator, heater controll valves, expansion tank.

The rest is aluminum, stainless, and iron.

I wouldn’t expect a flush to do anything to rubber.

Maybe your oil cooler lines have cooked out due to proximity to the exhaust manifold.

 

[Wedgy]

Or a previous owner dumped some stop leak in. I hesitate to use the corrosive flushing agents as I have seen it eat the seal out of a water pump twice, but I would use it if I was about to change all that stuff out. Might be a bunch of stuff clogged in the radiator. Sounds like it's cold there and you need the heater, otherwise I would just run water in the radiator for a couple weeks and keep flushing it until clean, but that might not be an option for you.

 

[brillo_76]

Or a previous owner dumped some stop leak in. I hesitate to use the corrosive flushing agents as I have seen it eat the seal out of a water pump twice, but I would use it if I was about to change all that stuff out. Might be a bunch of stuff clogged in the radiator. Sounds like it's cold there and you need the heater, otherwise I would just run water in the radiator for a couple weeks and keep flushing it until clean, but that might not be an option for you.

I was thinking that. I was wondering if some stop leak is in the mix on this one. Quite a possibility.

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[BostonJon]

My vote is also for a stop leak product. Those tend to coagulate and come out as a sandy residue. I had the same issue when replacing my heater core earlier this year (total PITA project) but was able to flush it out with distilled water before refilling with Toyota red.

 

[T4R2014]

Check hoses. Flush it with powdered dish soap mixed with distilled. You might need to backflush the system.

 

[BikeIdiot]

And nothing you removed was degraded on the inside?

AFAIK

Rubber = oil cooler lines, radiator hoses, heater hoses, IAC hoses, RTV sealant, thermostat seal.

Plastic = radiator, heater controll valves, expansion tank.

The rest is aluminum, stainless, and iron.

I wouldn’t expect a flush to do anything to rubber.

Maybe your oil cooler lines have cooked out due to proximity to the exhaust manifold.

Thanks for this. I'll start my hunt.

 

[BikeIdiot]

Radiator hoses could be degenerating on the inside? Oil cooler hoses?

Replaced the radiator. But not the oil cooler.

 

[BikeIdiot]

Or a previous owner dumped some stop leak in. I hesitate to use the corrosive flushing agents as I have seen it eat the seal out of a water pump twice, but I would use it if I was about to change all that stuff out. Might be a bunch of stuff clogged in the radiator. Sounds like it's cold there and you need the heater, otherwise I would just run water in the radiator for a couple weeks and keep flushing it until clean, but that might not be an option for you.

I thought the same thing. It's cold now and I need the heat. I was going to do the distilled water / multi flush thing but the garage has a '57 chevy overhaul and a Miata frame/body swap projects going on. I don't want to leave it with just water with temps in the low 20s. I may try this in the spring if I cannot solve it.

Going to replace the water pump next week.

 

[BikeIdiot]

I've changed out the coolant 4 times over the past 12 months and cannot seem to solve it. I didn't do a full drain of the block. Might try that next.