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Old 01-27-2016, 05:43 PM   #1
caddyfreak2
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"91 Caprice heater question

The heater of my '91 Caprice is not as warm as it used to be. I've heared that flushing the heater core with a garden hose can solve this problem. Has anybody done this?
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Old 01-28-2016, 03:40 PM   #2
Tech II
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Re: "91 Caprice heater question

Basically what you do it, when the vehicle is at normal operating temp, you feel the inlet hose, and the outlet hose from the heater core.......they should both be hot, and same temp.....if the inlet is much hotter than outlet, then there is possibly a blockage, and a reverse flush might work.....

Also, you have to check if there is an external flow control valve attached, usually, to the inlet hose.....it is vac actuated or cable actuated.....if the valve is not fully opening, you can have low heat.....

Are you losing coolant? Is it low in the reservoir or radiator? If yes, you can be creating an air pocket that will restrict coolant flow.....
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Old 01-29-2016, 05:25 PM   #3
j cAT
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Re: "91 Caprice heater question

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Originally Posted by caddyfreak2 View Post
The heater of my '91 Caprice is not as warm as it used to be. I've heared that flushing the heater core with a garden hose can solve this problem. Has anybody done this?
using a water hose to flush out the heater core with the hoses disconnected from the engine usually works. if you live in a cold climate you need this done whenever you change the coolant. also use distilled water with the coolant you normally use. it is best to use the same type coolant and manufacturer . as was mentioned both hoses hot means you do have flow . if no heat then it may be a heater control issue as there are temp doors that adjust for cold or heated function.
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Old 01-30-2016, 09:44 AM   #4
caddyfreak2
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Re: "91 Caprice heater question

Hi,
Thanks for your answers. How can I check if the valve still works or not? I'm not losing coolant and the hose that goes in is warm but the other hose is far less warm. So either it needs a flus or a new valve.
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Old 01-30-2016, 12:43 PM   #5
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Re: "91 Caprice heater question

Do you see a valve?

If there is none, and there is a difference in temp, yes, reverse flush the heater core.....the hot hose is usually the inlet....so put water in the outlet side, when you remove the hoses....

I use vise grips on the hoses before I remove them , to save on loss of coolant.....when flushing is done, then I attach the lower hose first, attach clamp, remove the vice grip and if coolant starts to come out of the other heater core outlet, then I attach the other hose(keep vice grip on).....then I remove the vice grip, and pivot the hose so air can leak out of the top of the hose/outlet connection.......

if nothing comes out, with the second hose on, not clamped, start the engine, the water pump will build up some pressure........again, pivot the the second hose so that air can burb out, and then push hose on outlet and clamp it......
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Old 01-30-2016, 04:47 PM   #6
j cAT
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Re: "91 Caprice heater question

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Originally Posted by caddyfreak2 View Post
Hi,
Thanks for your answers. How can I check if the valve still works or not? I'm not losing coolant and the hose that goes in is warm but the other hose is far less warm. So either it needs a flus or a new valve.
I doubt you have a flow valve. disconnect the heater engine hoses put one in bucket ,put water hose in the other ,,, then see how it flows . then reverse. if you mess with the heater core hose connections @ the core , you could break the heater core , unless you know what your doing. most GM vehicles use temp doors not flow valves . last I seen a flow valve was in a 1980's GM. could have been a 1970's though. my 84 doesn't have a valve .
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Old 02-01-2016, 04:45 PM   #7
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Re: "91 Caprice heater question

Ok, thanks all, I'll start with flushing the heater core.
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Old 02-01-2016, 07:28 PM   #8
rhandwor
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Re: "91 Caprice heater question

http://www.rockauto.com/ sells a heater control valve for a 91 Caprice.
Check if it getting vacuum to the heater control valve. Feel both sides of the valve for flow when open.
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