'87 Heater control valve leaking
Thread Starter
Drifting
Joined: Nov 1999
Posts: 1,801
Likes: 2
From: St. Paul MN
'87 Heater control valve leaking
My son's '87 Coupe, the vacume controlled water valve located near the firewall on the right side of the car. The valve is leaking. The valve is integral to the supply and return lines, hard pipe for about 1.5 feet with some bends. I don't think it would be hard to plumb in a vacume valve with some 5/8" heater pipe. The question I have is about the crossover that seems to be under the valve. It looks to me like if the valve is in the closed position it diverts the hot water back through the return line. I think this might be needed since this is a Z51 car with the Modine oil/coolant oil cooler. Anybody know of a vacume water valve that has that bypass capability? Dealer has discontinued the part, and all the Vette part suppliers I've checked also have. I'd rather get the exact replacement but don't think I can. Thanks for any help.
Thread Starter
Drifting
Joined: Nov 1999
Posts: 1,801
Likes: 2
From: St. Paul MN
One other question about this. There is a small coolant line running from the coolant supply line to the rear of the intake manifold, just to the right of the distributor area. Is that important? I don't have that on my mini-ram car so I just capped it off on the pipe on mine.
Thread Starter
Drifting
Joined: Nov 1999
Posts: 1,801
Likes: 2
From: St. Paul MN
But you don't live in Minnesota. I've seen 2 degrees on the outside temp display on mine. I never managed to get the car out on below zero days but I wonder if GM programmed a minus into it.
I'm just about to replace the valve with a coupla ball **** valves from the hardware that can be manually opened and closed. Then in the spring and fall they can be left open and during the hot months they can be closed to prevent water from going to the heater core.
I'm just about to replace the valve with a coupla ball **** valves from the hardware that can be manually opened and closed. Then in the spring and fall they can be left open and during the hot months they can be closed to prevent water from going to the heater core.
Race Director
Joined: Sep 2000
Posts: 17,298
Likes: 33
From: The Top of Utah
Originally Posted by Bob86ZZ4
But you don't live in Minnesota. I've seen 2 degrees on the outside temp display on mine.
RACE ON!!!
Last edited by CFI-EFI; Oct 26, 2006 at 07:54 PM.
Instructor
Joined: Jun 2006
Posts: 165
Likes: 0
From: louisvlle ky
I think he might have got a little confused, I know when I read it I did. not untill I read the last post you did that I knew what you mean. not to defend or start anything just something I noticed. Where is this valve and how hard is it to bypass.
Race Director
Joined: Sep 2000
Posts: 17,298
Likes: 33
From: The Top of Utah
As per my genuine GM Corvette parts book, "VALVE, HTR WAT SHUTOFF". It is located on the right side of the engine, very close to the firewall. It uses short hoses to connect to the heater core pipe nipples. Maybe yours is bypassed, too. They were only used from 1984 - 1987. The 1984 and 1985 used unique part numbers. The 1986 and 1987 shared a third number.
RACE ON!!!
RACE ON!!!
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
Top 10 Most Expensive Corvettes Ever Sold on Bring A Trailer
Brett Foote
10 Things Every Corvette Owner Needs (2026 Edition)
Michael S. Palmer
8 Most "Only Corvette Owners Understand" Quirks and Problems
Pouria Savadkouei
10 Reasons the C6 Z06 is Still A Performance Benchmark After 20 Years
Joe Kucinski
How Much Horsepower Every Corvette Engine "LOST" in 1972
Joe Kucinski
Top 10 DOs and DON'Ts for Protecting Your Convertible Top!
Michael S. Palmer
Top 10 Most Explosive Corvettes Ever Made: Power-to-Weight Ratio Ranked!
Joe Kucinski
150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter
Joe Kucinski
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
Race Director
Joined: Jun 2004
Posts: 13,963
Likes: 709
From: WI
There is no heater control valve on mine, the heater core gets water full time. If you want to use the valve you could try 'vette salvage places. I ran new heater hose with mine, the stock hoses were in pretty bad shape and getting a new stock hose was funny in cost.
Thread Starter
Drifting
Joined: Nov 1999
Posts: 1,801
Likes: 2
From: St. Paul MN
Goodness CFI. Yes, when I read your reply and saw you said you haven't had a heater, and then you put a comma in. That made me think you don't have a heater, or water control valve. Sorry very much for my terribly abusive response about living in MN. I know I can just pipe on by the valve, but that would mean hot water running to the heater core in the summer which I would think would add some heat to the cockpit, and there is no a/c on this car. I went to the store and bought some valves and t's and water pipe and such so I'm going to try to cobble up something and see if it works. I'll post some pic's if I get it to work. Sorry for groveling for some replys too, I guess I just thought my thread made it to the second page awful quick and somebody that had done the repair might have missed it. Race on!
Team Owner
Joined: May 2002
Posts: 24,337
Likes: 25
From: San Diego , CA Double Yellow DirtBags 1985..Z51..6-speed
CFI's repair is halfassed (and hypocritical too), but I don't blame him, as that heater control valve, at least for 85, is discontinued and the remaining n.o.s. ones are priced insanely high. You'd be better off making one fit from another application.
While we're on the subject, what does the vacuum hookup do? Does that open the valve more when the engine is at idle (and the water pump is turning slower) in attempt to maintain steady flow through the core?
While we're on the subject, what does the vacuum hookup do? Does that open the valve more when the engine is at idle (and the water pump is turning slower) in attempt to maintain steady flow through the core?
Instructor
Joined: Apr 2003
Posts: 204
Likes: 9
From: Ocean Springs MS
I had the same problem with the leaky valve on my 85. With the valve on the car, I cut it out of the pipe with a dremel tool, and replaced it with longer hoses. I capped off the vacuum line, and hid it in the harness. It looks neater than original, and I noticed no change in interior temp at all. And its very hot here in the summer.
Race Director
Joined: Sep 2000
Posts: 17,298
Likes: 33
From: The Top of Utah
Originally Posted by CentralCoaster
CFI's repair is halfassed (and hypocritical too), but I don't blame him, as that heater control valve, at least for 85, is discontinued and the remaining n.o.s. ones are priced insanely high.
Originally Posted by CentralCoaster
While we're on the subject, what does the vacuum hookup do?
Originally Posted by Bob86ZZ4
Goodness CFI. Yes, when I read your reply and saw you said you haven't had a heater, and then you put a comma in.
RACE ON!!!
Thread Starter
Drifting
Joined: Nov 1999
Posts: 1,801
Likes: 2
From: St. Paul MN
Originally Posted by CFI-EFI
Mine has been eliminated on my car. I haven't had a heater, water, control valve for over 18 years. No problems.
RACE ON!!!
RACE ON!!!
Also, the vacuum doesn't open the valve. It closes it to stop water from entering the heater core. That way the default if there is a vacuum problem would be to have heat. If you always have hot water in the heater core and you turn the vent on doesn't that run fresh air through the heater core and into the cockpit? Or is there some sort of trap door involved?
Race Director
Joined: Sep 2000
Posts: 17,298
Likes: 33
From: The Top of Utah
Originally Posted by Bob86ZZ4
My gosh, I'm seeing a comma after the word "heater" in your post.
Originally Posted by Bob86ZZ4
That makes it read like you don't have a heater.
Originally Posted by Bob86ZZ4
All of the parts descriptions I've found for the valve list it as a "heater control valve." No mention of the word water in the description.
Originally Posted by Bob86ZZ4
Also, the vacuum doesn't open the valve. It closes it to stop water from entering the heater core. That way the default if there is a vacuum problem would be to have heat.
Originally Posted by Bob86ZZ4
If you always have hot water in the heater core and you turn the vent on doesn't that run fresh air through the heater core and into the cockpit? Or is there some sort of trap door involved?
RACE ON!!!
Team Owner
Joined: Jun 2002
Posts: 21,510
Likes: 0
From: On a Wisconsin Death Trip
Originally Posted by CFI-EFI
The words heater and water have commas as should any multiple adjectives before their subject noun.
Hey Bob, sounds like the car's giving you guys some fits. Hopefully it stops acting up soon. Probably just getting used to the new owners.
Team Owner
Joined: May 2002
Posts: 24,337
Likes: 25
From: San Diego , CA Double Yellow DirtBags 1985..Z51..6-speed
Originally Posted by Bob86ZZ4
Also, the vacuum doesn't open the valve. It closes it to stop water from entering the heater core.
This is correct, I recall now, when I removed it a few weeks ago, the valve was open without vacuum.
Thread Starter
Drifting
Joined: Nov 1999
Posts: 1,801
Likes: 2
From: St. Paul MN
Jim, not a big problem. We did a cool plumbing thing on it and it seems to work good. It doesn't look that good though, so I'm not probably going to post any pictures. We were over watching the Laguna Seca Speed World Challenge with John Boos today and we showed him the car and he scratched his head. I convinced him that I plumbed it properly and he thought it looked pretty cool then.
And, this thread has taken an ugly turn since somebody wants to argue English and semantics.
And, this thread has taken an ugly turn since somebody wants to argue English and semantics.