Under-hood vacuum hose replace
Thread Starter
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BF Guru
Joined: Dec 2016
Posts: 5,610
From: Moscow, ID
Funny thing, my 1982 Honda Prelude has very many more rubber vacuum lines than my Blazer yet those originals are in perfect shape all these years later.
Are you referring to the plastic tubing for the tee fitting, the vacuum check valve (a one-way vacuum valve), and the fittings to the intake manifold? If so, yes they can be replaced and replacements can be found. If the nipple for the vacuum reservoir has broken off, then that is a more difficult item to replace because of its position. However, I would think a stand-alone vacuum reservoir from an earlier Blazer or S10 could be easily retrofitted if needed.
Funny thing, my 1982 Honda Prelude has very many more rubber vacuum lines than my Blazer yet those originals are in perfect shape all these years later.
Funny thing, my 1982 Honda Prelude has very many more rubber vacuum lines than my Blazer yet those originals are in perfect shape all these years later.
Funny how that happens....
Christine, I bought an OEM Vacuum Reservoir and installed it in my '02 Blazer. The reservoir has two nipples. One larger than the other one. All photos that I see of earlier S10's have one hose going from/to the check valve, and the other hoses are in place. But this smaller inlet/outlet has no line to go to it. So, naturally, I put a hose on it, and plugged it with a bolt. It seems that my cab vents are functioning correctly, with the strange exception of hot air takes a while to come out. The flow is good, but on a cold morning, when I warm up the vehicle, the warm air only flows when I accelerate. After that, it's all good. That's not what I'm used to,but it beats nothing, I guess.... Anything else to look for with that hose?
Thread Starter
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BF Guru
Joined: Dec 2016
Posts: 5,610
From: Moscow, ID
Christine, I bought an OEM Vacuum Reservoir and installed it in my '02 Blazer. The reservoir has two nipples. One larger than the other one. All photos that I see of earlier S10's have one hose going from/to the check valve, and the other hoses are in place. But this smaller inlet/outlet has no line to go to it. So, naturally, I put a hose on it, and plugged it with a bolt. It seems that my cab vents are functioning correctly, with the strange exception of hot air takes a while to come out. The flow is good, but on a cold morning, when I warm up the vehicle, the warm air only flows when I accelerate. After that, it's all good. That's not what I'm used to,but it beats nothing, I guess.... Anything else to look for with that hose?
As for the heat, there is what is called a "slave door" that works to direct heat through the heater core but if the rest of the vacuum system is ok, then that one normally is ok too. The temperature, amount of heat, is controlled by an electro-mechanical device, the Blend-Door Actuator. But when those fail, they tend to stop working all-together with the blend-door stuck either in the full hot or full cold position.
When you say you only get heat when you accelerate, are you saying that the air flow is strong and to where you direct it but only when you accelerate the engine (even when not in gear) will the temperature rise? And then, once the air coming out is at a warmer temperature it stays at that warmer temperature? I ask as normally when the engine goes faster, there is less vacuum rather than more. It is hard to imagine how changing the engine speed could help but these vacuum systems are funny. Some of the vacuum actuators work both ways with needing vacuum on both sides. But there also could be some lack of coolant flow through the heater core itself I guess.
But it does sound like things are working much better. Did you also check the one-way valve to make sure it is working fine?
Did you get one of those earlier ball-shaped vacuum canisters?
As for the heat, there is what is called a "slave door" that works to direct heat through the heater core but if the rest of the vacuum system is ok, then that one normally is ok too. The temperature, amount of heat, is controlled by an electro-mechanical device, the Blend-Door Actuator. But when those fail, they tend to stop working all-together with the blend-door stuck either in the full hot or full cold position.
When you say you only get heat when you accelerate, are you saying that the air flow is strong and to where you direct it but only when you accelerate the engine (even when not in gear) will the temperature rise? And then, once the air coming out is at a warmer temperature it stays at that warmer temperature? I ask as normally when the engine goes faster, there is less vacuum rather than more. It is hard to imagine how changing the engine speed could help but these vacuum systems are funny. Some of the vacuum actuators work both ways with needing vacuum on both sides. But there also could be some lack of coolant flow through the heater core itself I guess.
But it does sound like things are working much better. Did you also check the one-way valve to make sure it is working fine?
As for the heat, there is what is called a "slave door" that works to direct heat through the heater core but if the rest of the vacuum system is ok, then that one normally is ok too. The temperature, amount of heat, is controlled by an electro-mechanical device, the Blend-Door Actuator. But when those fail, they tend to stop working all-together with the blend-door stuck either in the full hot or full cold position.
When you say you only get heat when you accelerate, are you saying that the air flow is strong and to where you direct it but only when you accelerate the engine (even when not in gear) will the temperature rise? And then, once the air coming out is at a warmer temperature it stays at that warmer temperature? I ask as normally when the engine goes faster, there is less vacuum rather than more. It is hard to imagine how changing the engine speed could help but these vacuum systems are funny. Some of the vacuum actuators work both ways with needing vacuum on both sides. But there also could be some lack of coolant flow through the heater core itself I guess.
But it does sound like things are working much better. Did you also check the one-way valve to make sure it is working fine?
Last edited by djbillyd; Mar 11, 2020 at 08:38 AM. Reason: Added a "kudo"!
Thread Starter
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BF Guru
Joined: Dec 2016
Posts: 5,610
From: Moscow, ID
Yeah, things are much better. I plan to check that my coolant levels are optimum as well. I had to replace the radiator last summer because the fan exploded and took the radiator, and the fan shroud, out. I refilled it with A/F, but really hadn't looked at it since. Figured that all of the new stuff, hoses, clamps, and all, coupled with seeing no leaks, or hearing no sizzles, that all was well. Gonna check top make sure. That was a suggestion by DonL. But thank you for your help. You're my new "Shero"!!!
Glad my posts helped!
KUDOS! My driveway is as level as a lake surface, but I think I can probably deal with it. I tell you, I manipulated the flow by reversing the hoses and it appears, at least for now, that the heat comes pretty quickly. Before, when I cranked up, and let the engine run for 5-7 minutes, the air from the outlet was ice cold. Yesterday morning, after doing the hose thing, it heated up as soon as it moved the Temp needle. But really, DonL's suggestion about the coolant, made the biggest difference. When I looked into the top of the radiator, it was dry. The reservoir was extremely low. I really hadn't checked it because I never had a problem with the heating temp until the vacuum hose replacement. I think the combination of you guys pointing me in the right directions has solved my problem. Thank you both!
Thread Starter
|
BF Guru
Joined: Dec 2016
Posts: 5,610
From: Moscow, ID
KUDOS! My driveway is as level as a lake surface, but I think I can probably deal with it. I tell you, I manipulated the flow by reversing the hoses and it appears, at least for now, that the heat comes pretty quickly. Before, when I cranked up, and let the engine run for 5-7 minutes, the air from the outlet was ice cold. Yesterday morning, after doing the hose thing, it heated up as soon as it moved the Temp needle. But really, DonL's suggestion about the coolant, made the biggest difference. When I looked into the top of the radiator, it was dry. The reservoir was extremely low. I really hadn't checked it because I never had a problem with the heating temp until the vacuum hose replacement. I think the combination of you guys pointing me in the right directions has solved my problem. Thank you both!
Starting Member
Joined: Jun 2020
Posts: 1
Actually, the light-green line is the one that supplies vacuum to everything else. It is connected to a port on the left side of the upper intake plenum.
My 1999 transfer case is only electronically controlled with no vacuum hoses attached to it.
As for the HVAC line, yes it goes through the firewall below and to the outside of the brake vacuum assist can. It goes to the HVAC controller
If you can direct the air flow of the HVAC system to the window and to the instrument panel but not down below for heat, yes, you might have a mechanical issue. Hopefully the fix will be something simple such as reattaching the actuator arm.
My 1999 transfer case is only electronically controlled with no vacuum hoses attached to it.
As for the HVAC line, yes it goes through the firewall below and to the outside of the brake vacuum assist can. It goes to the HVAC controller
If you can direct the air flow of the HVAC system to the window and to the instrument panel but not down below for heat, yes, you might have a mechanical issue. Hopefully the fix will be something simple such as reattaching the actuator arm.
Can someone send a pic of where on the intake that line should run? Would be super helpful.