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New heads and strange coolant leak

2920 Views 7 Replies 4 Participants Last post by  docvette
Introduction out of the way in that section now on to the issue at hand!

Subject: 85 Chevy 1/2 ton, GM Goodwrench 350 4 bolt, aproximately 8000 miles. Performer Intake, Edelbrock carb, Headman headers, Erson cam, roller rockers, new Dart Iron Eagle heads.

Son and I just compelted a head swap on the engine.
We replaced the stock heads with Dart Iron Eagle's and all seemed to go well. Old heads off, cleaned deck surfaces thouroughly, installed Fel-Pro head gastkets dry as per directions, used new ARP head bolts with sealer on threads, torqued in sequence and double checked twice to make sure every bolt was indeed torqued correct. Put everything back together and fired it up....sounded great, set timing, idle mixture watched water level in radiator, when thermostat opened added water as needed. Checked heads for leaks in visible and obvious places still all seemed good.
After about 10 minutes of run time noticed what looked like coolant leak dripping low off the bottom of the engine on passenger side. Crawled under truck and sure enough clean water with a little left over antifreeze dripping from the pan gasket flange in between where the starter is bolted on and the pan. It looks as though it is comming from the pan itself but this makes no sense to me becuase it is clear, no oil contamination. Dropped the oil to see if there was water in the oil and there were no bubbles or milky signs to the oil. I have checked the back of the heads and there doesn't seem to be any leakage on the back of the block area.
Any help would be appreciated I am stumped!
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I'm not familiar with Dart heads for the SBC but it is entirely conceivable that you might need to put some silicone sealant on the header bolts. If they extend into one of the cooling passages it would allow a small amount of coolant to leak out and run down the side of the block and show up dripping off the pan.

Centerline and Mark both made good points.

Are you 100% sure the leak is not coming from the head bolts? What type of sealer did you use? Try running the engine for e few minutes (enough to get warm but, not hot). Pull off a valve cover on the side that's leaking and see if you spot any drops of water running out from under the head bolts. I have had a problem in the past with ARP thread sealer.

Thanks guys will check these areas out when I get home and let you know if I come up with anything! We did use a small bead of silicone around the water passages on the intake when we installed it but that's not to say there it wouldn't leak anyway....

Camaroman7d, yes we wid use ARP thread sealer on the bolts, I did not pull a valve cover last night because when I noticed the leak and I thought it was actually leaking past the pan gasket we shut it down to keep it from doing any more damage than necessary. Will change the oil this evening and give it a check to see.
If it turns out to be the head bolts (very well could be with that sealer) you can remove one at a time and re-seal them. I suggest using Permatex thread sealer. I have had GREAT success with it.

Just an update:

Went back and rechecked the head bolts and sure enough found a lower one on the head seeping water as Camaroman7d suspected!!.... many thanks for all the tips from all you guys. Pulled and resealed the bolt with permatex thread sealer and no more leaks. A little tuning and we are now in business....what a difference a good set of heads make on a nice little hotrod pickup....thanks for all the help and advice!
Right On!!! thanks for posting back. Glad I was able to help. I wish someone would have warned me about the ARP thread sealer.

Every once in a while I get one right :thumbup:


Doc here:pimp:

First off, Glad to hear you got it fixed!

As For the water-jacket Block-off's , had similar problem on a Vette, that wasn't leaking so much as you'd notice it, but it wouldn't "Burp" the system and it had an air bubble in The water pump...

Consequently the temp gauge did "Excursions" From 160 to 240 and back again in about 1 minute oscillations. and it acted the reverse of an overheat...let it idle forever and it sat on it (with real good airflow over it) and it would rise and fall!

After much head scratching, replacement of the thermostat, flushes and back flushes Sealer In case of a pinhole leak gulping air, Sealer on the manifold bolts, I resigned myself to the fact I must have a cracked or warped manifold or heads...blowing hot gasses into the cooling system, after pulling the manifold I found it "Ate away" almost beyond repair at the front right and left rear block-off ports! (See Photo)

What made it so intriguing was that it was not using any noticeable water, nor did it actually overheat (except for the very first time the problem showed up..well above 260 degrees) and it did not "Act" like a hot ping, heater working fine, nothing to indicate the engine was hot..

Anyway, I was able to repair the manifold with high temp "Orange" sealer...and so far it seems to be doing fine...

Just thought I'd pass it along...

So you can have a leak and never see it!

Doc :pimp:


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