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96 Fleetwood, 94 Fleetwood, 07 CTS, & 94 Caprice Wgn
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I think I told you, but the best piece of advice I got about 15 years ago, was from "jayoldschool". Remove the passenger side seat, 4 bolts. Then cover that area with cardboard, so the bolts won't be sticking into you. Second, just in my experience, my first time I changed a heater core was on my 95 Roadmaster wagon, same family as your Caddy. I could not for the life of me, remove the hoses off the pipes coming out the firewall; which is part of the heater core. They were like glued on. So, after wasting 2 hours, I got out the hack saw blade and cut the copper pipes from the heater core, 5 minutes.

The original GM heater core lasted 17 years. The new, genuine made in Mexico replacement barely made 1 year.

Seeing you're going to change the hoses anyways; change the hoses, put it back together and check the heat. Maybe you won't have to change the heater core.

Tom
 

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Discussion Starter #22
I think I told you, but the best piece of advice I got about 15 years ago, was from "jayoldschool". Remove the passenger side seat, 4 bolts. Then cover that area with cardboard, so the bolts won't be sticking into you. Second, just in my experience, my first time I changed a heater core was on my 95 Roadmaster wagon, same family as your Caddy. I could not for the life of me, remove the hoses off the pipes coming out the firewall; which is part of the heater core. They were like glued on. So, after wasting 2 hours, I got out the hack saw blade and cut the copper pipes from the heater core, 5 minutes.

The original GM heater core lasted 17 years. The new, genuine made in Mexico replacement barely made 1 year.

Seeing you're going to change the hoses anyways; change the hoses, put it back together and check the heat. Maybe you won't have to change the heater core.

Tom

Okay,
I went out and cut the reducer out replaced the hoses with just 5/8's and a T plus a union, bled the system....a little bit of heat, then I turned it off the car, started it again...no heat.

Can a heater core pass coolant through it during a flush, lots of fluid, and still not produce heat?
 

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96 Fleetwood, 94 Fleetwood, 07 CTS, & 94 Caprice Wgn
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Pull the hoses off the two pipes protruding from your firewall. Connect them to the new heater core (hang it someplace). Start the car, if both hoses are hot.....voila!

Tom
 

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Discussion Starter #25
Pull the hoses off the two pipes protruding from your firewall. Connect them to the new heater core (hang it someplace). Start the car, if both hoses are hot.....voila!

Tom
Will do, that is an awesome trick btw, I thought about it, but I wasn't sure it would work for a test - thank you.

So, with that said besides the seat removal - any other tips or tricks?
 

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96 Fleetwood, 94 Fleetwood, 07 CTS, & 94 Caprice Wgn
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I've told you all my tricks, if I tell you any more, you'll be as smart as me.

Actually there is one, make sure you flush out the whole heating system (radiator and engine). If you don't you may plug up the new heater core with contamination.

Tom
 

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I've told you all my tricks, if I tell you any more, you'll be as smart as me.

Actually there is one, make sure you flush out the whole heating system (radiator and engine). If you don't you may plug up the new heater core with contamination.

Tom
^^ Best advice ^^
 

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68 DVC, 96 FLTWD Brgm, 11 CTS Premium (two)
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Just asking but are you sure the water pump is working 100% OK and the belt for it ?

When Tstat was out did you test it to see it working OK? ( hot water on stove and see what temp it begins to open)

Could the dampers in the HVAC vents just not opening when it heat mode ?
If changing to defrost hows the air temp there ?

Another way to assure all air gets out
If you take Tstat out again

Heat it up with hot water in a pan on stove
When Tstat is open use a hard pill like a Advil and as Tstat is shutting when taken out of hot water let it close with the pill in the way so that stat cannot fully close

Now when adding water being Tstat is partly open then all air will purge out surge tank (have heater on high)

Pill will simply desolve and not hurt anything

Better yet, put one of the GM / Bars Leak cooling system tablets in the t-stat while its open.

200K on the 1995 and 120K on the 1996 and no heater core issues so far...

Now if I could only get those little white window regulator guides from breaking in the doors...
 

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Discussion Starter #29
Hey Guys.

So here is the deal now. If I squeeze the hoses, all of them. I can release some air bubbles, not much, and I get "warm," air then it goes cold. I noticed the top heater hose is cool, not cold but coolish. Then after the T it is very hot like the bottom hose is. I circled in the picture. Could the coolant tank or maybe the T be causing an issue? I will replace the heater core - but who knows it may not fix it?
 

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The top 5/8 heater hose is the outlet. The bottom heater hose is the inlet. The bottom will always be a bit hotter.

The coupling in the bottom heater hose is a restrictor. They are directional for some reason. They clog up. It's a servicable part that costs very little online. The story is they were used because the water pump moves the coolant so fast heat. Restricting it was for better heat. IDK. Will work fine either way. I would guess better with the restrictor.

Something I noticed on these cars at the bone yards is the heater hoses would clog up. They would fill with a white or orange crusty mess. Not compleatly plugged, but definatly restricted. You squeeze em in some spots near the core curves & can feel the stuff inside crunching.

Besides basics like a bad engine thermostat, air in the system, clogged heater core / hoses / restrictor there is something else to check...

The HVAC blend door.
On these cars they used an electric blend door servo.
The factory manual has you pushing buttons on the HVAC programmer to read codes & position readings.
It's a mess.

There is a much easier way to check the blend door.
 

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Testing & quick fix of the blend door.
Nothing needs to be removed.

1. Open glove box
2. Look in left side / left corner / left top between glove box door and dash with light
3. You will see the black HVAC unit. On the side of the unit facing the glove box door is the bleed door servo. It's also black, flat, few inches big, screwed in, about 6 small wires comming out the bottom.
4. The blend servo also has a blue or green round part in the middle, about 3/8 big with flat screwdriver slot.
5. Look closer around that green screwdriver sloted part. There are 3 marks molded around the outside.
6. The marks are at 10:00, 12:00, & 2:00.
7. 10:00 is full hot, 12:00 is mixed hot / cold, 2:00 is full cold.
8. With the car running change the temp settings from full hot to full cold.
9. The slot should slowly move from 1 side to the other.
10. On full hot it should land on 10:00.
11. If not at 10:00, take a big screwdriver & turn it to 10:00.
12. Now try step 7 again. it may start working again because it was just stuck.
13. when at 10:00 the air comming out of the heater vents should be 140 degrees or higher.
 
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