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Mystery coolant leak

2016 Views 86 Replies 11 Participants Last post by  Wc203
Hey guys I have a coolant leak from my 4BT and am convinced it’s my freeze plug , but I wanted to do my due diligence first before pulling the trans and T case to make sure that’s what it is . There’s coolant leaking from the bell housing cover dripping down to my sway bar and trans . No other obvious leaks . And unfortunately no access to the rear freeze plug due to the AA adapter to my 4L85E trans…. Anyone have the Cummins # for the rear freeze plug or pictures so I can see what I’m working with , couldn’t find anything on the web.
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bad news, looks like the headgasket is getting ready to take a dump .
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It’s the head gasket unfortunately
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The one near the top of the block is covered by the Advanced adapters adapter plate , it’s very large , but based on what I saw , it’s leaking behind cylinder 4, not very happy about this, seems like it’s been one thing after another unfortunately
Make sure the head is not cracked, not common but rule it out....
not sure why it would have cracked , but I’ll get the head checked when I pull it off .
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while I have your guys attention, anyone have any kits they recommend for gaskets? Looking for a kit that has all necessary gaskets to replace while pulling the head.
Sweet thank you for your endless knowledge on these !!
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Here’s some pics of the head gasket the leak was behind the head above the trans steady leak , but no noticeable coolant mixing , a little ugly , not sure what made it go , high EGTS? High cylinder pressure ? Only running H1C for now , highest I’ve seen is 1300 climbing up a grade , will bump the timing back a little and hopefully head studs , and the new super 30 will help lower the EGTs to avoid another situation like this …
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I never touched the head bolts , I haven’t done anything with the head besides injection pump , timing , fuel pin , gov spring , injectors , so it’s a surprise they would be loose. One thing I did notice is when pulling the bolts the back head bolts were dry and the rest had oil
So turns out , my head is cracked in cylinder 1 and 2 also, getting kinda ridiculous…. Thought these things were supposed to be reliable haha. Anyone know where to source a good new 4BT Head ? CPL857 aftercooled.
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I called jegs , over 150 orders with no returns

Also ,do I need a specific head since mine is aftercooled ? I know mine has some pipes pressed . On the side and the top of the head , or will any new 4BT Head work!
I just don’t wanna buy a junk head but according to the website , same casting and thicker than OE
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Looks like I’ll go with the promaxx head. Just didn’t wanna buy Chinese junk !!
They’re 7
One question you need to think on. What size are your injector tips? Old heads has 9mm injector tips and those were known to crack. Cummins changed injector tips to 7mm in the early '90's and the problem went away. As far as I know, all new heads are 7mm but if your injectors are 9mm they aren't going to fit. You'll either have to change your tips to 7mm or get new injectors. Cummins doesn't even sell 9mm injectors anymore. They provide 7mm units and a 2mm sleeve to make them fit.
They’re 7mm , 9745 is the part number on the tip. I measured them.
Well regardless , I ordered the promaxx head, ARP headstuds from diesel tuff , super HX30W turbo , and a OEM Cummins gasket. And am now converting to NON IC (temporarily) instead of JWAIC… til I can save up enough to IC it ..
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You will have to have the rocker pedestals machined to use the studs. Not a big deal.
Doin that now 👍
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Need to save up for that intercooler real quick. At any kind of serious boost level your intake temp is going to be in the 300-400 deg F range. EGT's will range higher than normal too.
I was hoping running it non IC with the super 30 would actually lower EGTs.. since it’s not getting 180* air from the coolant
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