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Thread: What do you recommend?

  1. #1
    Registered User rcb280z's Avatar
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    Default What do you recommend?

    So after several months of running the alumaseal through the cooling system of my 77 280 I still have a coolant leak between the block and head.Click image for larger version. 

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ID:	74018Click image for larger version. 

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ID:	74019 I have contemplated re torquing the head bolts but am a little nervous. The last time I had the head off was in 1997 or there abouts. So its been awhile. Has anyone attempted this and what were the results? I was thinking of just breaking them loose (just barely) and then re torquing, in proper sequence of course. Im nervous because I believe I could take a chance of cracking the head if my leak is caused from a warped head. Ideas, experiences, and suggestions are appreciated.

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    Registered User LeonV's Avatar
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    Replace the head gasket. It's a relatively easy job on the L-series.
    2/74 260Z

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    That's a bummer. I can't remember if you said the engine had ever overheated but you might consider having another head ready to swap on. Depending on how many miles are on the current head and the odds of warpage. My leaking head didn't show any signs of combustion chamber leakage but is about .007" bent. Bowed up in the middle, but it leaked on the end.

    Retorquing won't crack the head, they're actually pretty flexible. The odds are probably against it fixing the leak though. I would just check the torque on each bolt to see if you had some loose ones that might explain the leak. Start with a low number and work up to spec. Good to know anyway, for future work. Maybe you had an older style gasket that was supposed to be retorqued after a few miles and wasn't, allowing a leak to develop.
    1976 280Z, with some minor modifications

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    Registered User rcb280z's Avatar
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    Leon, I am tossing that around as well. If I have to remove the head I should go on and do an "overhaul" of the complete engine. I want to do a compression test as well to determine whether or not to overhaul it.

    Zed, no on the overheating. The current head has 197,000 miles but had a valve job 97,000 miles ago. I do recall retorquing the head after so many miles when I had the head rebuilt. It was resurfaced but the block was not because the machine shop said it was "good", IIRC.

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    Just curious, but do you remember the brand of head gasket?
    1976 280Z, with some minor modifications

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    Registered User rcb280z's Avatar
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    Im thinking it was a felpro back then but not 100% sure. That brings me to another question, what would be the best gasket if I were only to replace the head gasket? Haven't decided which way to go yet. Just head gasket or whole overhaul. After 97,000 miles Im thinking overhaul. But I need to do compression test first before I decide.

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    Registered User LeonV's Avatar
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    A compression test is a good idea and if it shows any signs that something is wrong, make sure you check leak-down as well. If all is healthy, I'd take the head to the machine shop to get checked. An alternative is buying a used head as mentioned above, sending that head to the machine shop, and then just swapping heads.
    2/74 260Z

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    Registered User rcb280z's Avatar
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    Good idea as well Leon. Going to run compression test this week sometime and post results.

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    Default Compression test results

    All plugs out (plugs look really good), throttle open all the way, remote starter in hand, compression gauge hooked up and the results are from 1-6:
    150-170-155-152-172-170. Took another reading of the lower ones with identical results. I squirted a small amount of oil into the 3 lower cylinders, waited about 5 minutes and tested the 3 again. Here are those results:
    (1)152 (3)158 (4)152. Didn't raise the numbers enough to be considered a ring issue. The funny thing is, the engine burns 1/2 a qt of oil every 3 months which about 2300 miles. Now I'm thinking maybe I didn't squirt enough oil into those cylinders when I retested.
    Next I checked valves for those 3 cylinders and discovered they were off from .001-.002. After adjusting the valves I ran a compression test again and got the same numbers as the first test. If #1 cyl had around 170 then I could suspect the head gasket between 3-4 was "going" but, that wasn't the case. I must have more than 1 thing going on here. Coolant leak, maybe some valve issues. Anyway, I'm still not sure what I'm going to do or should do next.

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    Registered User rcb280z's Avatar
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    ZedHead, I remembered something....I did use the felpro gasket. Now I see they are "perma-torque". I don't remember that when I replaced the HG 97,000 miles ago.

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    Registered User LeonV's Avatar
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    You can do a leak down test but those compression numbers aren't awful. I bet some valves are just not sealing as well as the others. If your oil consumption isn't the rings, it could be the valve stem seals, an item that gets replaced during a head job.
    2/74 260Z

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    Yeah Leon I agree the numbers aren't awful. Because I couldn't manipulate the numbers on those cylinders with some oil I'm assuming the valves are not sealing as good as they should be. So I will start looking for an engine overhaul kit because like I said before if I take the head off I may as well do a complete overhaul. My timing chain is on "number 2" mark so it has stretched. There are a couple of things leading me in the direction of overhauling the engine. The good thing about is I don't have to do it right away. That gives me some time to search for a good machinist and recommended engine overhaul kit. So with that said any suggestions on an engine overhaul kit? Anyone?
    Thanks.

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    I've had two local people with this same leak. Both were fixed by re-torquing the head bolts. If you do need to change the head gasket, then you have nothing to lose by giving this a try.

    Now just torquing them from their current tight position won't help, unless they are 1) loose, and 2) the threads are in excellent condition, neither of which are very likely. Whatever torque you apply is very unlikely to actually reach the threads and stretch the bolt properly. Take them out one at a time, same pattern as the torque method in the FSM (center to each end), clean the threads thoroughly, oil them, and put it back in, torquing in two steps.

    There are two bolts, the center ones I believe, that are prone to being quite corroded and may not come loose very easily. Take it easy on those two. Of course they are the ones closest to the leak....
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    Which is probably why they corrode easily...makes sense. Thanks zKars, That would be the easiest and cheapest direction for sure as long as the head doesn't crack on me. For some reason I have this fear of it cracking while "re-torquing". Not sure why if I follow the proper torquing sequence.

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    BTW, can I get away with not removing the intake and exhaust header or will that hinder the re-torquing process?

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    Quote Originally Posted by rcb280z View Post
    BTW, can I get away with not removing the intake and exhaust header or will that hinder the re-torquing process?
    Its best to remove the engine and remove all external equipment. Place the engine on an engine stand where you have nice and consistent foot and arm placement to ensure perfectly even torquing on all bolts.

    Or stop worrying and just go tighten the bolts.... You can do it, I know you can.
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    Things are only going to move a tiny fraction of a millimeter so the other attached parts won't be affected. Interested to see if it works. I tried on mine, but it was too far gone. Good luck.
    1976 280Z, with some minor modifications

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    Zed Head, I was hoping someone would say that.

    zKars, doing the work isn't an issue. It's "what can I avoid having to do". The back isn't so nice to me these days. So the less I have to do the better I am.

    Thanks guys. I will post results when I do this.

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    fyi - one of my center head bolts snapped when i was taking off the head - it was corroded. luckily, it broke off 1" above the deck, allowing me to (thankfully) twist it out with vice grips after some pb blaster. i immediately bought a full set of new head bolts, wasn't about to replace my head and do all that work with suspect fasteners. they are not cheap - a set is about $100. yikes.

    just saying... be careful with the "re-torque".
    '78 280z - Daily driver/work in progress...

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    I broke a center bolt also when I finally took my head off. May be best to use the torque wrench for loosening also. If you can't get it loose at some set percentage (10%, 20%) above the desired torque setting, maybe leave it and try something else. Once you break one you're committed to removal. Better plan some down time just in case.
    1976 280Z, with some minor modifications

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    Registered User rcb280z's Avatar
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    Iv'e decided to wait a couple of months when I can afford the time just in case.......... I will also buy a new set of head bolts just because. If I don't break one when removing them it could happen when re-installing them.

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