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On my '95 DeVille, 4.9 liter, The heater hose coming out of the water neck on the engine goes to a "T" fitting. One end of the "T" goes to the heater core. The inside of this "T" at the end that goes to the core is made smaller than the other 2 ends of the "T" but the outside is the same size all around to accept 3/4" hose.Does anyone out there know why it's smaller at the heater core end? The only thing I can think of is to slow down the volume of water going to the heater core, but why? All I know is, is that a simple "T" fitting costs only 3 bucks at the auto parts store where as the special "T" fitting costs 28bucks at the dealership. And of course mine broke while taking the hoses off to get to the rear spark plugs during a tune-up. :banghead:
 

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Angela Desmond said:
On my '95 DeVille, 4.9 liter, The heater hose coming out of the water neck on the engine goes to a "T" fitting. One end of the "T" goes to the heater core. The inside of this "T" at the end that goes to the core is made smaller than the other 2 ends of the "T" but the outside is the same size all around to accept 3/4" hose.Does anyone out there know why it's smaller at the heater core end? The only thing I can think of is to slow down the volume of water going to the heater core, but why? All I know is, is that a simple "T" fitting costs only 3 bucks at the auto parts store where as the special "T" fitting costs 28bucks at the dealership. And of course mine broke while taking the hoses off to get to the rear spark plugs during a tune-up. :banghead:
Unfortunately, it needs that restriction to maintain proper flow.
 

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Thanks Katshot but I wonder why it needs less pressure to the core. Maybe it can't take the pressure the coolant system produces. I haven't checked, but the old 425's had 18psi which was more than small block Chevys, so my engine swap into the Caprice will probably need a different heater core to match the 18psi the 425 uses.Does the 4.9liter also make 18psi? Anyway, I'll buy the right "T" fitting tommorrow so I don't blow out the heater core with the generic one I have in it's place temporarily :thumbsup:
 

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The "T" on my friends car cracked and started leaking... He went to Home Depot and bought the identical "T" for 3 dollars. But it only lasted one day since then ones that the hardware store sells are not design for high temperature like the one your Caddy dealer sells. By the way, I think he only paid like 15 dollars for his.
 

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on the tee valve(heater control valve) , one side is fed from a connection from the thermostat.....the other 2 legs of the tee i assume are feed and return lines from the heater core? is this correct? i am in the process of replacing the heater core(a nice little job!!!) but want to know where the feed and return lines from the core connect to . just abit bit difficult to follow
them!!!

txs

bernie
 

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If you do not use the restriction in the "T", you will have heat problems. I believe our old guru once said that the restriction was there to slow the flow and thus prevent heater core erosion from high flow rates. You could always use a standard "T" and make your own restriction.
 
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