Leaky cross over pipe that seems to not stop leaking no matter what I try.

[m1garand_man]

I have an issue that has been perplexing me for months now. I have a leak on the inside side of the left side coolant cross over pipe on my engine that no matter how diligently I try to seal won't stop leaking.

I originally tried to seal the leak about 24 months ago with new gaskets and red RTV which was what I used to use on almost everything that didn't touch oil. It would leak from the inside edge of the flange on the pipe and from the bolt hole even though I put RTV on the bolt threads and under the bolt head. It would leak intermittently and then this September it finally let loose.

So I took it apart after it got bad enough to drip on the ground and replaced the gaskets and used blue RTV. With in weeks the same thing happened. Leaking from the flange and bolt.

Last weekend I put non hardening gasket maker on the bolt threads and underside of the head and for now the leaking has stopped from the bolt but its still coming out of the inside edge of the flange. The gasket and blue RTV I put on a month ago are still on there.

I am in Fairbanks Alaska and it has been single digit temps outside which hasn't helped but in my mind I shouldn't leak either way if I did it right.

The only thing I can think is that when I did the gasket this time I drove it home from the shop I was working at. But other than this I have never had problems driving a short distance on wet RTV.

Once it gets bad enough to drip on the ground again I will re do the thing in my garage and not fill the coolant up until everything has 24 hours to drive but I am getting tired of re doing this again and again.

What gives? What am I missing? I am scraping the old gasket stuff off and cleaning the surfaces. Nothing is scored, scratched or obviously out of level. I am letting the RTV set up for 15 minutes before assembly and going finger tight and then snug after 10 more minutes starting with the inside bolts first. The right side has never leaked on me either. I just don't get what I am missing.

I know the truck is 28 years old but I pride myself in having a leak free truck.

 

[Westech]

I would use a flat file and make sure the pipe flange and head are flat. I bet something is warped or maybe cracked. Make sure it's flat and not cracked and just try using paper gaskets and no rtv. Put a little pipe dope on the blots and that's it.

 

[cucvrus]

I am guessing a cracked coolant crossover manifold. That is a 4K mile guess. With out seeing it. Gaskets alone will be a challenge. I use Permatex The Right Stuff. That is my opinion only. It works for me. I have seen these coolant manifolds cracked before. They are easily cracked if tightened unevenly. This is a shot at helping you out. I may be wrong so it is only a suggestion. Good Luck and let me know if I can be of further assistance.

 

[ODFever]

I spent 20 years dealing with bitter cold when I lived near Buffalo, NY. I absolutely HATED having to do any auto maintenance in sub-zero temperatures. I feel your pain, sir. {shudder}

I wonder if the single digit temperatures are preventing the RTV from curing and adhering completely. Do you have access to a heated shop where you could park the truck for a while and let everything warm up so you can apply the gasket material and let it cure?

 

[Drock]

All good points, I'd like to add, that it's best to let the vehicle sit for 24 hours before you start it. This lets the RVT cure completely before putting pressure on it. And I'm sure with the cold weather up there it's taking much longer to cure.

 

[nyoffroad]

When I use RTV I bolt up the parts and leave them loose overnight, then the next day tighten them up. I'd remove the tube completely and check for a crack, if good I'd clean the mating surface's and try again. Have the heads been off the engine? Reason I ask is if a machine shop decked them to remove a warp then that would change the distance between the heads and may cause a problem. Thats a long shot thou.

 

[m1garand_man]

I spent 20 years dealing with bitter cold when I lived near Buffalo, NY. I absolutely HATED having to do any auto maintenance in sub-zero temperatures. I feel your pain, sir. {shudder}

I wonder if the single digit temperatures are preventing the RTV from curing and adhering completely. Do you have access to a heated shop where you could park the truck for a while and let everything warm up so you can apply the gasket material and let it cure?

Actually I park it in my heated garage every night. Its 65F in there.

 

[m1garand_man]

When I use RTV I bolt up the parts and leave them loose overnight, then the next day tighten them up. I'd remove the tube completely and check for a crack, if good I'd clean the mating surface's and try again. Have the heads been off the engine? Reason I ask is if a machine shop decked them to remove a warp then that would change the distance between the heads and may cause a problem. Thats a long shot thou.

I will try this when I get around to taking them apart again.

The heads are not original to the engine but they were not re-decked either. I got them from Boyce and bolted them on. No leaks from the heads save from an unrelated and as of yet un diagnosed oil leak into the right rear exhausts port. I say into because there is oil on top and below the exhaust manifold but its a leak that has been there since month one with these heads, not one that seems to cause appreciable oil loss or extra smoke. So who cares. But like I said that one is unrelated and on the complete opposite end of the head.

 

[Hasdrubal]

I had a similar leak issue with the aluminum cross over pipe, new gaskets and perma-tex didn't work. Took it off again and gave it a close inspection. Hairline crack found in mounting flange. It had been on the motor, leak-free for 5 years previously.

 

[cucvrus]

That hairline crack will do it everytime. It is easy to do on these 6.2 coolant manifolds. Uneven tightning and you don't have to turn hard to crack the aluminum. I just glue the felpro gaskets on finger tighten the bolts and torque them evenly and fill the coolant system and it is ready to roll. Change both the rear ones while you have the coolant down. Same gaskets. Keep it rolling.