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Old 06-25-2007, 07:51 PM   #1
JBVETT
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Default Flow Restrictor ?

I am about to remove the flow restrictor valve on the hose leading to the heater core on my stock 94 cpe LT1 to check for buildup. Has anyone ever had problems with just replacing the piece with a straight tube or will the pressure be to high? (Search didn't cover this)

Last edited by JBVETT; 06-25-2007 at 10:05 PM. Reason: correction
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Old 10-02-2009, 11:39 AM   #2
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__________________
95-Lt1-auto-Polo-Conv, 125hp ZEX N2O dry, LE Cam 226/234 565/565 109LSA, Comp Pro Mag 1.6rr, Patriot Xtreme Springs, PCMFORLESS tune, K&N, AO Ram Air, 52mm TB, EM LT Headers, No Muffler, X-pipe, Meziere HD EWP, Vigil 2800 Conv, TransGo Shift Kit, Pro-Built 4L60E Trans., 24lb SVO's, MSD Coil & 8.5mm wires, NGK TR6 plugs, B&M TransCooler, Dewitt Radiator, 160 therm, TB AirFoil, 3.07 Rear Axle, LT4 KM, S&D Rotors, SS BrakeLines, Hawk HPS Pads, ZR1 rims 275/315. 1967-Firebird-conv-2spd-326ci
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Old 10-07-2009, 05:20 PM   #3
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Quote:
Originally Posted by clean94 View Post
I am about to remove the flow restrictor valve on the hose leading to the heater core on my stock 94 cpe LT1 to check for buildup. Has anyone ever had problems with just replacing the piece with a straight tube or will the pressure be to high? (Search didn't cover this)
Do not eliminate the restrictor. If you do, it'll probably cost you a heater core.

Live well,

SJW
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Old 10-07-2009, 05:35 PM   #4
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Originally Posted by SJW View Post
Do not eliminate the restrictor. If you do, it'll probably cost you a heater core.

Live well,

SJW
I just eliminated mine last week. Do you know for sure that the restrictor is to protect the heater core? What source did you get the info from? I've been asking around on the forums for some time and have never been able to get a straight answer.

Here was someone elses explaination...
"Actually, the restrictor is to prevent overcooling via the heater core. The idea is that in extremely cold weather the heater running will prevent the motor from coming up to temp since the heater is on the bypass side, so it runs the real risk of overcooling the motor during the warmup phase. The restrictor is to make sure the motor comes up to temp as quickly as possible and due to the size of the heater core/piping it allows for adequate hot coolent flow to provide ample heat to the interior/defroster.

I may add that the reason the piping isn't smaller is because the higher volume of coolent has better thermal stability."



I have a Mezierre HD EWP installed. I was hopping that since the pump is electrical and does not turn as high of rpms like the stock mechanical pump that I will be ok if damage to the core is the concern. Although if the above explaination is correct than it is a matter of cooling and I should have nothing to worry about any way. I have found a few people that have deleted it and havent had any problems with the heater core over a few years time.

Hopping to get the correct answer on this.

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Old 10-07-2009, 10:27 PM   #5
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Hey, Rick.

My advice was based upon an article that appeared in a recent ASE publication that was specific to numerous Ford vehicles, which was in turn based upon a Ford factory TSB if I recall correctly. Granted, this article wasn't speaking about Corvettes, but given the recommendation for Fords, I wouldn't remove the restrictor on any car. I'd say you're courting trouble if you do.

GM also speaks to this issue, if I'm not mistaken, in TSB 05-06-02-001 (I don't have a copy of this TSB that would allow me to verify this, but if you can get a copy I think you'll find that the recommendation is that a flow restrictor can help to reduce abrasive erosion of the heater core).

Live well,

SJW



Quote:
Originally Posted by rickreeves1 View Post
I just eliminated mine last week. Do you know for sure that the restrictor is to protect the heater core? What source did you get the info from? I've been asking around on the forums for some time and have never been able to get a straight answer.

Here was someone elses explaination...
"Actually, the restrictor is to prevent overcooling via the heater core. The idea is that in extremely cold weather the heater running will prevent the motor from coming up to temp since the heater is on the bypass side, so it runs the real risk of overcooling the motor during the warmup phase. The restrictor is to make sure the motor comes up to temp as quickly as possible and due to the size of the heater core/piping it allows for adequate hot coolent flow to provide ample heat to the interior/defroster.

I may add that the reason the piping isn't smaller is because the higher volume of coolent has better thermal stability."



I have a Mezierre HD EWP installed. I was hopping that since the pump is electrical and does not turn as high of rpms like the stock mechanical pump that I will be ok if damage to the core is the concern. Although if the above explaination is correct than it is a matter of cooling and I should have nothing to worry about any way. I have found a few people that have deleted it and havent had any problems with the heater core over a few years time.

Hopping to get the correct answer on this.

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Old 10-07-2009, 10:38 PM   #6
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Quote:
Originally Posted by SJW View Post
Hey, Rick.

My advice was based upon an article that appeared in a recent ASE publication that was specific to numerous Ford vehicles, which was in turn based upon a Ford factory TSB if I recall correctly. Granted, this article wasn't speaking about Corvettes, but given the recommendation for Fords, I wouldn't remove the restrictor on any car. I'd say you're courting trouble if you do.

GM also speaks to this issue, if I'm not mistaken, in TSB 05-06-02-001 (I don't have a copy of this TSB that would allow me to verify this, but if you can get a copy I think you'll find that the recommendation is that a flow restrictor can help to reduce abrasive erosion of the heater core).

Live well,

SJW


Thanks for the info. I was looking for something solid to go on as opposed to the theories I was getting. I'll try to research this some more with the info you gave. Are all heater cores made from the same metal? Do you think I'll be safer since I have an electric water pump?

__________________
95-Lt1-auto-Polo-Conv, 125hp ZEX N2O dry, LE Cam 226/234 565/565 109LSA, Comp Pro Mag 1.6rr, Patriot Xtreme Springs, PCMFORLESS tune, K&N, AO Ram Air, 52mm TB, EM LT Headers, No Muffler, X-pipe, Meziere HD EWP, Vigil 2800 Conv, TransGo Shift Kit, Pro-Built 4L60E Trans., 24lb SVO's, MSD Coil & 8.5mm wires, NGK TR6 plugs, B&M TransCooler, Dewitt Radiator, 160 therm, TB AirFoil, 3.07 Rear Axle, LT4 KM, S&D Rotors, SS BrakeLines, Hawk HPS Pads, ZR1 rims 275/315. 1967-Firebird-conv-2spd-326ci
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Old 10-07-2009, 10:46 PM   #7
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Found this so far...

TSB #05-06-02-001: Information on Aluminum Heater Core and/or Radiator Replacement

The following information should be utilized when servicing aluminum heater core and/or radiators on repeat visits. A replacement may be necessary because erosion, corrosion, or insufficient inhibitor levels may cause damage to the heater core, radiator or water pump. A coolant check should be preformed whenever a heater core, radiator, or water pump is replaced. The following procedures/ inspections should be done to verify proper coolant effectiveness.

Technician Diagnosis
Verify coolant concentration. A 50% coolant/water solution ensures proper freeze and corrosion protection. Inhibitor levels cannot be easily measured in the field, but can be indirectly done by the measurement of coolant concentration. This must be done by using a Refractometer J 23688 (Fahrenheit scale) or J 26568 (centigrade scale), or equivalent, coolant tester. The Refractometer uses a minimal amount of coolant that can be taken from the coolant recovery reservoir, radiator or the engine block. Inexpensive gravity float testers (floating *****) will not completely analyze the coolant concentration fully and should not be used. The concentration levels should be between 50% and 65% coolant concentrate. This mixture will have a freeze point protection of -34 degrees Fahrenheit (-37 degrees Celsius). If the concentration is below 50%, the cooling system must be flushed.

Inspect the coolant flow restrictor if the vehicle is equipped with one. Refer to Service Information (SI) and/or the appropriate Service Manual for component location and condition for operation.

Verify that no electrolysis is present in the cooling system. This electrolysis test can be performed before or after the system has been repaired. Use a digital voltmeter set to 12 volts. Attach one test lead to the negative battery post and insert the other test lead into the radiator coolant, making sure the lead does not touch the filler neck or core. Any voltage reading over 0.3 volts indicates that stray current is finding its way into the coolant. Electrolysis is often an intermittent condition that occurs when a device or accessory that is mounted to the radiator is energized. This type of current could be caused from a poorly grounded cooling fan or some other accessory and can be verified by watching the volt meter and turning on and off various accessories or engage the starter motor. Before using one of the following flush procedures, the coolant recovery reservoir must be removed, drained, cleaned and reinstalled before refilling the system.

Last edited by rickneworleansla; 10-07-2009 at 10:52 PM.
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Old 10-07-2009, 10:48 PM   #8
SJW
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Originally Posted by rickreeves1 View Post


Thanks for the info. I was looking for something solid to go on as opposed to the theories I was getting. I'll try to research this some more with the info you gave. Are all heater cores made from the same metal? Do you think I'll be safer since I have an electric water pump?

Most older vehicles used copper/brass heater cores. Nearly all newer vehicles use aluminum cores. I have no idea about whether the electric pump would be more or less friendly toward your heater core.

Live well,

SJW
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Old 10-07-2009, 10:49 PM   #9
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I'd say your research is off to a good start. Happy hunting!

Live well,

SJW


Quote:
Originally Posted by rickreeves1 View Post
Found this so far...

TSB #05-06-02-001: Information on Aluminum Heater Core and/or Radiator Replacement

The following information should be utilized when servicing aluminum heater core and/or radiators on repeat visits. A replacement may be necessary because erosion, corrosion, or insufficient inhibitor levels may cause damage to the heater core, radiator or water pump. A coolant check should be preformed whenever a heater core, radiator, or water pump is replaced. The following procedures/ inspections should be done to verify proper coolant effectiveness.

Technician Diagnosis
Verify coolant concentration. A 50% coolant/water solution ensures proper freeze and corrosion protection. Inhibitor levels cannot be easily measured in the field, but can be indirectly done by the measurement of coolant concentration. This must be done by using a Refractometer J 23688 (Fahrenheit scale) or J 26568 (centigrade scale), or equivalent, coolant tester. The Refractometer uses a minimal amount of coolant that can be taken from the coolant recovery reservoir, radiator or the engine block. Inexpensive gravity float testers (floating *****) will not completely analyze the coolant concentration fully and should not be used. The concentration levels should be between 50% and 65% coolant concentrate. This mixture will have a freeze point protection of -34 degrees Fahrenheit (-37 degrees Celsius). If the concentration is below 50%, the cooling system must be flushed.

Inspect the coolant flow restrictor if the vehicle is equipped with one. Refer to Service Information (SI) and/or the appropriate Service Manual for component location and condition for operation.

Verify that no electrolysis is present in the cooling system. This electrolysis test can be performed before or after the system has been repaired. Use a digital voltmeter set to 12 volts. Attach one test lead to the negative battery post and insert the other test lead into the radiator coolant, making sure the lead does not touch the filler neck or core. Any voltage reading over 0.3 volts indicates that stray current is finding its way into the coolant. Electrolysis is often an intermittent condition that occurs when a device or accessory that is mounted to the radiator is energized. This type of current could be caused from a poorly grounded cooling fan or some other accessory and can be verified by watching the volt meter and turning on and off various accessories or engage the starter motor. Before using one of the following flush procedures, the coolant recovery reservoir must be removed, drained, cleaned and reinstalled before refilling the system.
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Old 10-07-2009, 10:56 PM   #10
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Seem to me, the system pressure would put more strain on the core than the pressure of fluid pumping through ? I think I have a 17# cap on my radiator.
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Old 10-07-2009, 11:09 PM   #11
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Originally Posted by JackDidley View Post
Seem to me, the system pressure would put more strain on the core than the pressure of fluid pumping through ? I think I have a 17# cap on my radiator.
I think the idea is that the restrictor will reduce flow rate, thus also reducing abrasive erosion. I don't think it's as much a pressure issue...

Live well,

SJW
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Old 10-07-2009, 11:34 PM   #12
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Quote:
Originally Posted by SJW View Post
I think the idea is that the restrictor will reduce flow rate, thus also reducing abrasive erosion. I don't think it's as much a pressure issue...

Live well,

SJW
hmm.. Makes sense. I found little pieces of debris inside the restrictor I removed. Eventually they would have worked their way free though.

I regularly flush the system once a year but it seems almost impossile to keep it 100% clear. The radiator and water pump are new. I havent changed all the hoses yet or the heater core. Those arent cheap or easy so I think I'll wait on that.

Anyone know if they make metal restrictors? The reason I took the plastic one off is because it was leaking at the ends. If I over tighten it will break just like the last one.

I wonder if putting some type of servicable filter in there would serve the same purpose. http://www.jag-lovers.org/xj-s/book/CoolantFilters.html

Last edited by rickneworleansla; 10-07-2009 at 11:36 PM.
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Old 10-08-2009, 11:44 PM   #13
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I'm sure Chevrolet never intended for the restrictor to act as a filter, although undoubtedly some larger debris gets caught in some of them. The goal was to reduce the volume of coolant flowing through the core in order to reduce the amount of abrasive erosion of the core's innards. If there's less coolant moving through the core, and if it's moving more slowly, any abrasive materials that are suspended in the coolant won't do as much to abrade the core.

A filter is an interesting idea, but I'd only consider placing it in one of the heater hoses, where it wouldn't be a disaster if it got too clogged (in fact, that'd make it a flow restrictor in its own right, wouldn't it?). I surely wouldn't put one in the radiator hose, as the guy with the Jag did in the link you provided. I don't want anything other than a normally-functioning thermostat interfering with the flow through my radiator.

Live well,

SJW


Quote:
Originally Posted by rickreeves1 View Post
hmm.. Makes sense. I found little pieces of debris inside the restrictor I removed. Eventually they would have worked their way free though.

I regularly flush the system once a year but it seems almost impossile to keep it 100% clear. The radiator and water pump are new. I havent changed all the hoses yet or the heater core. Those arent cheap or easy so I think I'll wait on that.

Anyone know if they make metal restrictors? The reason I took the plastic one off is because it was leaking at the ends. If I over tighten it will break just like the last one.

I wonder if putting some type of servicable filter in there would serve the same purpose. http://www.jag-lovers.org/xj-s/book/CoolantFilters.html

Last edited by SJW; 10-08-2009 at 11:49 PM.
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Old 10-08-2009, 11:44 PM
 
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