Slant 6 leaking from water pump bolt.

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Mineallmine

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I have a 63 Dart that I am finishing off a restoration of and ran into an issue. When I got the car it had the core plugs out and new ones in a box to replace them (they were corroded through). Thus, it had no coolant when I got it. I removed the engine and went over the engine with all new gaskets and new timing gear and chain, as well as new water pump. Also had the valves lapped. Never did a lot as the engine ran good before and is supposed to be lower mileage. Here's where the issue comes in.

When I replaced the water pump the bolt on the lower side of the rad hose connection (the one that goes into the water jacket) broke. I was able to drill and extract it. I noticed when I replaced the bolt it seemed sloppy. When I filled it with water (didn't use coolant as I'm in a heated garage and wanted to check for leaks and also flush it one more time after testing the cooling system) I found water leaking from that bolt. I did apply a little sealant to it but It won't tighten up. It feels like it will strip if I pull on it.

I am looking at a couple options to repair it and am looking for opinions/other suggestions.

First option is to drill/tap it to accept a 7/16 bolt. Not sure though if the 3/8 hole is too close in size to properly do this and get a good strong thread that wont leak (with thread sealant of course).

Second is to drill it out to accept a 3/8'-16 x 1/2"-14 E-Z Lok thread insert. Not a fan of a Helicoil as it's in a water jacket and never had lots of luck with those. Concern here is if there's enough material on that "ear" on the block to allow me to drill it up to a 1'2" threaded hole without breaking off.

I was also considering trying the 7/16" bolt repair and if that doesn't work use the insert. I was reading and if I'm correct, the tap outer diameter for a 7/16" bolt is 0.4375" while the drill used for the insert is 29/64" or 0.4531". Again, still a little concerned about that tap thickness.

Also, if I was to try the 7/16" tapped repair would I be able to accomplish this without removing the water pump? One less step and less parts required would be nice.

Any suggestions or past experience would be appreciated.

This is the insert I'm considering:

3/8-16 x 1/2-13 E-Z LOK Threaded Insert for Metal | Buy a 3/8-16 x 1/2-13 Carbon Steel Threaded Insert - E-Z LOK
 
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Get a time sert kit for threads. Then go to fastenal and buy the correct length stud so you can use all the threads with a sealant on them . Your issue will be solved.
We stock and sell 1000's of Time Serts. Most items are in stock.
Biggest issue with a stud (I was going to oversize it and just use a stepped stud) is that due to location it would be very difficult to install with that very short bypass hose needing to be installed right above it. Don't think I'd be able to push the water pump onto the hose then pivot the pump onto the stud.

Looked at the time sert kit. the inserts are actually 0.2" larger diameter than the E-Z Lok inserts. Otherwise they basically look the same. Is there something different about them that would make them a better choice?
 
I think 10 mm metric bolt is just slightly bigger than a 3/8". That could be a possibility.
 
I think 10 mm metric bolt is just slightly bigger than a 3/8". That could be a possibility.
I think the hole is too damaged for a bolt that close in size. Great idea though. Less than .5mm difference in diameter would probably result in the same issue.
 
Biggest issue with a stud (I was going to oversize it and just use a stepped stud) is that due to location it would be very difficult to install with that very short bypass hose needing to be installed right above it. Don't think I'd be able to push the water pump onto the hose then pivot the pump onto the stud.

Looked at the time sert kit. the inserts are actually 0.2" larger diameter than the E-Z Lok inserts. Otherwise they basically look the same. Is there something different about them that would make them a better choice?
 
Looks like the Time-sert has the smallest Diameter and seals the hole with a flanged top the expands in the hole
 
Looks like the Time-sert has the smallest Diameter and seals the hole with a flanged top the expands in the hole
Funny, I just watched that video last night as well. The timesert and the E-Z lok compared similarly in the testing. The ez lok I had ordered was the thin wall one so it was actually a hair thinner than the timesert. THe standard ez lock is thicker.

Either way, looks like both would do well for a repair like this. In my case it is no longer a requirement.

I did a bunch of research and measuring and decided to try the 7/16 bolt repair first, as I could still move up to the insert repair. I pulled the rad and fan off the engine and went to drill it out to 23/64 and the drill slid in. No threads left basically. Went up to 3/8 that my tap calls for and it didn't do much going in, but it did take some. I had to pull the water pump to tap the hole though. I guess it was just off enough that the tap couldn't line up directly with the hole. It tapped nice and left a nice clean thread. I put the bolt in and it was nice and snug. Reassembled it all using sealant on the threads of that bolt and it tightened up nice. Filled it up and no more leaks. Even ran it for half an hour to get it up to temperature and no leaks detected. I do think I have an air lock in my heater core though. The one hose is hot and the other is warm/cold. I flushed out the heater core when I had it all apart and it was flowing really smooth and clean so I doubt it is plugged. Temp is good and thermostat seems to be opening as the upper hose gets easy to compress. Going to try to bleed the heater core tomorrow maybe to see if its full of air.
 
Air being trapped in those cores never was never much of an issue. Is there a heater control valve in the line on that one that could be stuck shut?
 
Nope. Just a straight through flow. Will have to look into it better tomorrow.
 
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