Cooling system vacuming
Thread Starter
Safety Car
Joined: Jan 2004
Posts: 4,549
Likes: 343
From: Glastonbury CT
Cooling system vacuming
On a C4 if you can not get to the knock sensors for a cooling change can you vacuum the system? Also where would you attach to drain the block?I have a Mityvac vacuum cylinder (gallon give or take ) for liquid storage which came with the unit. Has any one tried this method?:
Melting Slicks
Joined: Jan 2014
Posts: 2,478
Likes: 254
From: Downers Grove Illinois
I don't see how that would work. Some have been known to drain from radiator only and fill with distilled water a few times until it comes out clear, then fill with coolant/distilled water. Be sure to start between cycles and run heater to flush out heater core. I think something like 5 cycles or so.
Thread Starter
Safety Car
Joined: Jan 2004
Posts: 4,549
Likes: 343
From: Glastonbury CT
cooler than hell
I don't see how that would work. Some have been known to drain from radiator only and fill with distilled water a few times until it comes out clear, then fill with coolant/distilled water. Be sure to start between cycles and run heater to flush out heater core. I think something like 5 cycles or so.
Drifting
Joined: Oct 2015
Posts: 1,674
Likes: 191
From: Shit Creek, USA
When I pulled my sensors, a flood of coolant was released from each. I'm with Jim. Don't see how you'll do a decent job without pulling the sensors.
It's not just about draining coolant, either. Knock sensors fail and/or seize in the block over time. Tons of threads on this forum where, especially the passenger side, gets stuck. Then you're in for some pain, because the wrench point is soft metal that breaks free.
As long as they're not seized, really a pretty easy task. What is keeping you from just pulling the sensors?
It's not just about draining coolant, either. Knock sensors fail and/or seize in the block over time. Tons of threads on this forum where, especially the passenger side, gets stuck. Then you're in for some pain, because the wrench point is soft metal that breaks free.
As long as they're not seized, really a pretty easy task. What is keeping you from just pulling the sensors?
Thread Starter
Safety Car
Joined: Jan 2004
Posts: 4,549
Likes: 343
From: Glastonbury CT
sucked it out
When I pulled my sensors, a flood of coolant was released from each. I'm with Jim. Don't see how you'll do a decent job without pulling the sensors.
It's not just about draining coolant, either. Knock sensors fail and/or seize in the block over time. Tons of threads on this forum where, especially the passenger side, gets stuck. Then you're in for some pain, because the wrench point is soft metal that breaks free.
As long as they're not seized, really a pretty easy task. What is keeping you from just pulling the sensors?
It's not just about draining coolant, either. Knock sensors fail and/or seize in the block over time. Tons of threads on this forum where, especially the passenger side, gets stuck. Then you're in for some pain, because the wrench point is soft metal that breaks free.
As long as they're not seized, really a pretty easy task. What is keeping you from just pulling the sensors?
Melting Slicks
Joined: May 2013
Posts: 2,692
Likes: 349
From: Sacramento California
I'm glad the vacuum worked for you but the block may still have sediment. I agree with the others, you really should pull the knock sensors for a proper flush. It's not very hard.
Drifting
Joined: Oct 2015
Posts: 1,674
Likes: 191
From: Shit Creek, USA
Skip this step at your own peril.
Safety Car
Joined: Sep 2004
Posts: 3,953
Likes: 550
From: Mission Viejo CA
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Thread Starter
Safety Car
Joined: Jan 2004
Posts: 4,549
Likes: 343
From: Glastonbury CT
Melting Slicks
Joined: Oct 2016
Posts: 2,024
Likes: 363
From: Central Alabama
I'll just say this.
I pulled my knock sensors yesterday on my 92. I have the entire cooling system apart. Since the water pump was already off, the amount of coolant in the block was a little lower than it would be.
When I was done I measured it and there was one US gallon that came out. Think about that. Even after pulling all the hoses and the water pump there was still a gallon in the block.
Why on earth would you not pull the knocks? Was this a case of changing the coolant without lifting the car?
It took all of 15 minutes and 4 tools to drain the block. Ratchet universal adapter and a 2 sockets.
I pulled my knock sensors yesterday on my 92. I have the entire cooling system apart. Since the water pump was already off, the amount of coolant in the block was a little lower than it would be.
When I was done I measured it and there was one US gallon that came out. Think about that. Even after pulling all the hoses and the water pump there was still a gallon in the block.
Why on earth would you not pull the knocks? Was this a case of changing the coolant without lifting the car?
It took all of 15 minutes and 4 tools to drain the block. Ratchet universal adapter and a 2 sockets.
Last edited by belairbrian; Oct 23, 2017 at 04:39 PM.
Melting Slicks
Joined: May 2013
Posts: 2,692
Likes: 349
From: Sacramento California
I'll just say this.
I pulled my knock sensors yesterday on my 92. I have the entire cooling system apart. Since the water pump was already off, the amount of coolant in the block was a little lower than it would be.
When I was done I measured it and there was one US gallon that came out. Think about that. Even after pulling all the hoses and the water pump there was still a gallon in the block.
Why on earth would you not pull the knocks? Was this a case of changing the coolant without lifting the car?
It took all of 15 minutes and 4 tools to drain the block. Ratchet universal adapter and a 2 sockets.
I pulled my knock sensors yesterday on my 92. I have the entire cooling system apart. Since the water pump was already off, the amount of coolant in the block was a little lower than it would be.
When I was done I measured it and there was one US gallon that came out. Think about that. Even after pulling all the hoses and the water pump there was still a gallon in the block.
Why on earth would you not pull the knocks? Was this a case of changing the coolant without lifting the car?
It took all of 15 minutes and 4 tools to drain the block. Ratchet universal adapter and a 2 sockets.
The vacuum method used by the OP is pretty effective and likely removed most of the coolant from the block. So it's not really necessary to pull the knock sensors to do a coolant change. The issue here is the potential for leaving behind sediment deposits, which could cause hot spots and promote corrosion in the cooling jackets (both caused by poor/incomplete coolant circulation). Sediment deposits in the cooling jackets will only come out when the knock sensors are pulled and the jackets are physically cleaned out (pressure washer, hose nozzle, length of wire, etc). It's not guaranteed that there is sediment, but with the age of our cars, it's not worth taking the risk. So I fully agree, if you're going to maintain the cooling system, spend an extra 20 minutes and clean out the block properly.