TR4/4A TR4 coolant leak thru head bolt

[derickson]

I'm new to the forum, and midway through rebuilding my 1963 TR4. I've had the engine out, had the crank turned, replaced the crank bearings, rebuilt the head, put it back together, rebuilt the SU H6s, clutch/brake hyraulics, fuel pump...
I've got two challenges:
1. I have a slow coolant leak up past one of the head bolts next to the valve cover. The coolant appears to be coming up the threads of the head stud and the nut. What's causing it?
2. I've rebuilt the SU jets twice, and the right one still leaks fuel slowly. I've already checked the floats, replaced the check valve (with the Grose version), replaced the seals with o-rings, but it still leaks. What gives?

Thanks for any help.

 

[AltaKnight]

I'm not familiar with the 4 cyl engine but I'll give it a go.
1) The head stud is likely drilled and tapped into a water passage, this is normal on many cars, that being said, you will need to remove the stud (probably tricky to do with the head in place, you might be able to double nut it) and use a gasket sealant on the threads when you put it back in, there's many types on the market, I like that blue stuff.
2) The fuel level in the bowl is probably set too high so that it probably also weeps around the gasket on the bowl, this usualy gives very rich mixture also. You need to set the fuel level in the bowl correctly per the manual.
Oh and by the way welcome to the forum, lots of friendly people here with good LBC knowledge.

 

[derickson]

Graham,
thanks for the reply. I'll investigate the thread sealant. I'm curious if anyone else has seen this and traced it back to the head gasket, since from the manual it's clear that's a possibility.
On the carbs, I set the float level per the manual when I rebuilt them. I'll check again.

 

[Bugeye58]

Is the jet leaking at the base of the carb, or is it weeping fuel into the throat?
If it's weeping at the top, make sure the bowl vents are clear.
Jeff

 

[Geo Hahn]

I recall a similar problem (coolant leak at a head bolt on TRactor engine) not too long ago -- a search of the archives might turn it up.

 

[Bugeye58]

DE, did you retorque the head after running the engine?
Jeff

 

[TR3Mod]

I had this once on my TR3. It turned out to be a very tiny crack in the block from the bolt hole outwards to the outside edge of the block. If I recall it was the one nearest the fire-wall on driver's side. I was not in a position to do major repairs at that time, so I carefully 'v'd' the crack with a die grinder and used JBweld. Before doing this I removed the stud and cleaned the treads as well as flushed out the internal threads with brake-clean. I then used Loctite thread locker on the stud. after the JBweld cured I worked the surface down to the block's machined surface. As mickey-mouse as all this sounds, it's still holding- 15 years later! This may or may not be your problem. Whatever you do, don't decide to add bar's leak or similar products to you coolant! Good luck.

TR3Mod

 

[derickson]

Thanks for the responses. The jet is leaking at the base of the carb, not into the throat. When I put my finger on the base of the jet where the choke linkage attaches to the jet, it's damp with fuel. I'm wondering if it's the internal copper gaskets in the jet assembly, since I've checked the float height several times, and the jet continues to leak slowly for hours after the engine is stopped.
On the coolant leak, I did re-torque after running, but still have the leak. It's also a slow leak, just enough fluid to sit without dripping around the top of the head stud/nut thread interface and evaporate off as the engine runs, but always still some fluid sitting there. My next attempt will be to loctite the threads before replacing the nut, and hope that seals the leak. It's remarkable, actually, when you consider how small the area and how long the path to the top of the stud. I'm still wondering if I should pull the head again and check the head gasket for leaks. Any thoughts?