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Thread: Question about the mainifold warmup loop in the cooling system 1972 240Z

  1. #1
    Registered User sdyck's Avatar
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    Default Question about the mainifold warmup loop in the cooling system 1972 240Z

    I had a leak on my Manifold Heater Hose, (Rear Intake Manifold to Rear Tube, on a 1972 240Z), and replaced it with a 1/2" generic line. It was quite a struggle getting things back together, the hard line that runds behind the engine neer the fire wall has a bracket that bolds on with the rearmost exhaust manifold stud. It looks like the braket that holds the hard tubing should be adjustable but I couldn't get it to move, its either welded to the tube or coroded so badly its stuck.

    The two hard tubes I'm connecting are offset by 1/4 of an inche, so the rubber tubehas a bit of a bend in it that's putting more strain on the tubing than I like.

    My question is; is that braket actually welded on or should I be able to free it up?
    I had a leak on my Manifold Heater Hose, (Rear Intake Manifold to Rear Tube, on a 1972 240Z), and replaced it with a 1/2" generic line. It was quite a struggle getting things back together. The hard line that runs behind the engine near the fire wall has a bracket that bolts on with the rearmost exhaust manifold stud really made getting things back together difficult. It looks like the bracket that holds the hard tubing should be adjustable but I couldn't get it to move; itís either welded to the tube or corroded so badly itís stuck.

    The two hard tubes I'm connecting are offset by 1/4 of an inch, so the rubber tube has a bit of a bend in it that's putting more strain on the tubing than I like.

    My question is; is that bracket actually welded on or should I be able to free it up? The bracket end that hold the tubes simply wraps around it with an open end, it looks like I should be able to bend it open, move the tube and bend it closed.

    Thanks,

    Steve

    Thanks

  2. #2
    Rust Free'ish zKars's Avatar
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    Steve:

    The bracket is welded to the tubing. There is supposed to be a temp sensitive valve at the back of the manifold (turns off the flow when the engine temp is hot), then a bit of hose to the hard line. If any of that has been "modified" then the fitment is going to suffer. I have a few of all the bits and pieces that are supposed to be there if you want to look at how its supposed to be set up.
    -----------------------------------------
    Jim
    73 240Z HLS30 149331
    69 510 PL510 77603

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    Registered User siteunseen's Avatar
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    Here's mine. I was too scared to mess with the one at the thermostat housing but changed the back one. I cut the old hard and brittle one off with a razor knife then the newer rubber was bendable to get it on.
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    1972 240Z #918 New Sight Orange
    1977 280Z #305 Light Blue Metallic
    1972 240Z #110 Persimmons Red

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    Registered User sdyck's Avatar
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    Jim, I'll take you up on that offer at some point, Thanks!

    Siteunseen, thanks for the pictures. Itís interesting your set-up is a little different than mine. The little rubber hose you replaced is the one I'm dealing with. I seem to have an additional item coming from the manifold; the gap between the two hard pipes is at most half an inch. I think you may be missing the temperature sensor Jim was referring to, #8 in the attached picture.
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    Registered User Hunter260Z's Avatar
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    Ok Guys

    Please get me straight on this setup.I have some friends in the Triangle Z Club that just plugged off the intake and thermostat. I don't see that to be a problem in NC because I don't drive mine that much in the winter. So if I plugged off the intake and thermostat would that cause a dead zone and a rise in the temperate and create the Z to run hot.
    Ray
    1974 Datson 260Z
    RLS30-27748 Matching #'s
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    Purchased 5/23/1974

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    Registered User siteunseen's Avatar
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    Interesting. Here's that part on a set of SUs I just bought. The above pictures are on my February '72 model that I honestly don't think had the part. Maybe someone with more knowledge on the different types will know for sure. The car runs great and starts right up, sometimes without any choke. I see you live waaay up there so you may need it but if it's replaceable, it's removable.
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    1972 240Z #918 New Sight Orange
    1977 280Z #305 Light Blue Metallic
    1972 240Z #110 Persimmons Red

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    Registered User siteunseen's Avatar
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    Quote Originally Posted by Hunter260Z View Post
    Ok Guys

    Please get me straight on this setup.I have some friends in the Triangle Z Club that just plugged off the intake and thermostat. I don't see that to be a problem in NC because I don't drive mine that much in the winter. So if I plugged off the intake and thermostat would that cause a dead zone and a rise in the temperate and create the Z to run hot.
    Here's a pretty good circulation diagram to look at. Except for the potential to leak at those connections, I don't see a reason to delete it.
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    1972 240Z #918 New Sight Orange
    1977 280Z #305 Light Blue Metallic
    1972 240Z #110 Persimmons Red

  8. #8
    Boat Anchor Repairman Captain Obvious's Avatar
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    Quote Originally Posted by siteunseen View Post
    Interesting. Here's that part on a set of SUs I just bought. The above pictures are on my February '72 model that I honestly don't think had the part.
    Yup, that's the thermostat that's supposed to be on the coolant lines through the manifolds. I'm assuming that most of them have failed or corroded thru over the years and have been discarded and replaced with simple nipples instead. That would be my explanation as for why you don't have one on your car right now. Can't tell from the pic, but is the nipple on the rear carb made out of brass? If so, it's clearly a later mod.

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    Boat Anchor Repairman Captain Obvious's Avatar
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    Quote Originally Posted by Hunter260Z View Post
    if I plugged off the intake and thermostat would that cause a dead zone and a rise in the temperate and create the Z to run hot.
    I'm no cooling system expert, but I think it's important to have a small amount of flow through the thermostat housing, even when the engine is cold. If that area is completely stagnant, then you run the risk of overheating because the thermostat won't be subjected to the hot water and could instead be sitting in a stagnant cold pool.

    I believe most thermostats have a small bypass hole built into them to allow for just this kind of issue, but I wouldn't completely block off all those path(s) without first confirming that is the case.

    Eventually heat will make it's way into that area through conduction and eddy currents, but if you don't ensure some flow somewhere prior to the thermostat getting hot enough to open, it may be too late by the time it does.

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    Registered User Pop's Z's Avatar
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    FWIW, I removed all the manifold coolant lines and the piping that goes around the back of the block due to some corrosion,and leaky hoses. The result has been that it takes about a minute longer to warm up even when I take the car out on winter days for a bit of exercise. I suppose if you lived in a really cold place and drove your car on a daily basis then it would not be advisable, but for me it's just less worry about leaky coolant lines. There has been no issue with overheating.

    Cheers, Mike
    '73 240Z, 80,000 original miles, F54, N42 massaged and shaved (10.5-1 comp.), stage 2 cam, ZX ignition, Header, 2 1/2" exhaust w/ magnaflow muffler, 5 spd (Maxima), 4:11 R180 (200SX), 15" Rota RBs 205-60/15 Bridgestone Grid 109s, KYB struts, stock springs, rubber bushings, MSA sway bars and strut bars, HotRod Air hvac system, '90 300ZX seats, upgraded sound system, BRE-type spook and spoiler

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