Water leak between head and block on a L24 engine in a 1971 240z

[robertsjeff]

I have a 1971 240z that I have been restoring eight years the end of next month 8/13. I had a machine shop rebuild my engine which took the guy two plus years to do. I finally got it in the car and went with thriple Dcoe 40 triple carbs and the engine runs fine. I noticed a month or so after the engine was in the car that there was a small amount of coolant on the block where there are tabs on the block that stick out past the head. I pressurized the cooling system and dropped pressure so I pulled the head off took it to a different machine shop and had them pressure test and put a straight edge on the head and they told me it was good and I told them what happened and who did the motor. They told me the real hard jobs the sub out to the guy that did my engine. The guy that did my engine grew up in a machine shop that his dad owned and the guy is now around 50 and doing engines his entire adult life so he suposably knows what he is doing. I told him what was going on and he said I waited to long to start it and when I did I did not run it long enough. I don't remember his exact words but it's like the head gasket was a rear main seal or something. I alway thought the thing either leaks or does not and told the guy the thing was not a rear main seal or something that drys up. I then pulled the three webers, intake and what not then the head. The guy used a felpro gasket and it looked ok but I bought a new one and installed it, torqued the head to specs and started it again and it appeared fine but a week later I noticed a small amount of coolant along the edge of the block where it sticks out futher than the head. I checked the toque on the head bolts and they are to specs. I am getting pretty frustrated at this point I have spent almost 40k on the car so far and have had everything replaced with new and just when I think I can drive it the leak shows up. If the head was pressure tested and checked to insure it was straight and it still leaks it's got me stumped and a little mad. If anyone can give me some clue other than I waited to long to start the engine which is crap I would really appreciate it.

Thanks,

Jeff Roberts

[black gold man]

This is were you should have sent your engine. And you are right there.

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Rebello Racing

511 Wilbur Ave A5, Antioch, CA ‎

(925) 754-4871 ‎ · rebelloracing.com

[Wade Nelson]

I can think of several alternative causes for a repeat leak besides a machine shop that didn't do their job correctly.

One is a tiny crack in the head, which even the best machine shop is unlikely to find. It might require applying bluing or x-raying.

If the head is flat, has been milled slightly for a perfect surface, then that's unlikely to the cause of the problem.

So that points to the BLOCK side. How was the block prepared? Did someone use an abrasive wheel (3M zip disk) to remove old gaskets, and leave behind deep scratches? Or try to file it and not keep the file perfectly flat?

What about the gasket? Is it the correct gasket? For a 2.4, not a 2.6 or 2.8? Turned the wrong way? If you've had leaks with two Felpro's (best in the biz, imho) then I"d try a different one next time around. Who knows, maybe they had a manufacturing problem. And definitely give Fel-Pro a call; they're great guys and will bend over backwards to help you troubleshoot a problem!

What about your torque wrench. Is it a professional tool, calibrated within the past year --- and not dropped? What if you're simply not getting enough torque on the bolts? You could at least COMPARE it with a couple other wrenches.

Even mighty Subaru had some head gaskets they absolutely couldn't get to seal, brand new, and issued bulletins instructing frustrated techs replacing them to pre-emptively dump in a film-canister sized container of leak sealer (ground up pecan shells? aluminum powder?)...to seal microscopic head gasket leaks. Google it if you dont' believe me. And the cost is negligible.

[madkaw]

You did a pressure check on the head? So did you do a pressure check on the engine- while running- of the coolant system?

Not sure if I agree with FelPro being the best in the biz. I would shoot for a Nismo gasket. You did check to make sure the head gasket matched holes ?

The earlier the head the more chance of corrosion around the passages. Head is flat, but is the surface really clean around these passages with no pitting.

[Patcon]

I agree the head sounds flat but is the block flat, clean, true. Are all the head bolt holes tapped and chased. Did you use any lubricant on the head bolts. I don't know what the FSM recommends but ARP bolts require lube to get the right torque values. A small dose of stop leak might be an easy way out...

Charles

[olzed]

I agree the head sounds flat but is the block flat, clean, true. Are all the head bolt holes tapped and chased. Did you use any lubricant on the head bolts. I don't know what the FSM recommends but ARP bolts require lube to get the right torque values. A small dose of stop leak might be an easy way out...

Charles

Also a good idea to check that some of the head studs are not bottoming out in their holes.

[robertsjeff]

The head was milled and the block surface was clean and looked good when I pulled the head off. The Fel-Pro gasket matched up and with the timing chain portion of the head gasket it really only goes on one way. I used one torque wrench to check the bolts first time and then used my brother in-law's Snap On when I replaced the head gasket the first time. I had my brother in-law tell me maybe bars leak it but after spending the money I spent I was not sure if it would plug anything else up. The gasket matched the one that came off and was ordered for the 2.4 engine. I appreciate your help.

Thanks,

Jeff Roberts

[robertsjeff]

The head was milled and the block surface was clean and looked good when I pulled the head off. The Fel-Pro gasket matched up and with the timing chain portion of the head gasket it really only goes on one way. I used one torque wrench to check the bolts first time and then used my brother in-law's Snap On when I replaced the head gasket the first time. I had my brother in-law tell me maybe bars leak it but after spending the money I spent I was not sure if it would plug anything else up. The gasket matched the one that came off and was ordered for the 2.4 engine. I appreciate your help.

Thanks,

Jeff Roberts

[robertsjeff]

I have heard a lot of good things about Rebello Racing and had I know five years ago I would have driven the engine to Antioch but as usual a day late or five years in my case. I appreciate your feedback.

Thanks,

Jeff Roberts

[robertsjeff]

Steve,

I did pressure test the cooling system with the car running and when I did the leak between the block and head got worse. That's when I pulled the carbs, intake, and other items so I could pull the head and replaced the head gasket. The holes lined up on both gaskets and the surfaces looked and felt smooth with no pitting. I appreciate your help and feedback.

Thanks,

Jeff Roberts

[robertsjeff]

Charles, the machine shop used ARP bolts and when I replaced the head gasket I got a packet of the lube from the machine shop and used it. The machine work seems smooth and no pitting or scratches it looks and feels smooth. The block looks like it was milled and is real smooth. I did have the competition pressure test the head and checked with a straight edge and it appears to be fine. The engine runs fine and does not over heat it just has a slight leak. I have had a couple friends recommend stop leak but was not sure if I would do more damage then good with it. I appreciate your help and feedback.

Thanks,

Jeff Roberts

[robertsjeff]

Patcon,

If I am not mistaken all the head studs are screwed in all the way and they are the ARP bolts that the machine shop used and I used the recommended lube on them when I replaced the first head gasket. I appreciate the help.

Thanks,

Jeff Roberts