MC9 Radiator leak(s)?

[plyonsMC9]

Good morning bus folk,

Somewhere, around our re-cored radiator on the passenger side (our 1983 MC9 has two radiators), I have coolant leak(s).  I've spent a lot of time up there looking and am having trouble finding the source.  After having them replaced, I had a small issue w/ some of the hose clamps coming loose, but I've fixed those issues.  I've torqued those smaller clamps to 50 inch pounds and that stopped all leaking around those hoses.  

At the top of the radiator there is the hose that runs from the surge tank to the radiator, with a small, about 18 inches, hose.  It seems to be damp around the connector on the hose.  So I'm looking for a replacement for that just in case.  However, it doesn't seem likely that is the sole cause of the issue. Mechanic said 10 foot lbs torque for that connector, I think I was able to check that connection but it didn't seem loose.  I can give it another try if that is recommended.

The other area I have a question on is all those bolts around the top lip of the radiator, could those need tightening?  After the radiator was initially put back in and tested, nobody noticed any problems.  Only after it was driven a while in the mountains and deserts that this started.  

As usual, greatly appreciate your advice!

Kind Regards, Phil

[gumpy]

Looks like the gasket on the top tank is leaking. Did you replace that when you recored the radiator?

[plyonsMC9]

Thanks Craig,

The entire radiator was replaced.  (Both radiators were replaced).  The originals were not recored. 


- Phil

[Scott & Heather]

I bet the gasket is leaking too. Mine did on my 102C3. I tightened down all of the bolts along the top of the radiator and fixed that problem.


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[Iceni John]

When I recored my radiator it took several slight retightenings of the tanks' bolts until the gasket no longer compressed.   I then pressurized the radiator and tanks to exactly 10 PSI and made sure there was absolutely no pressure loss after 24 hours.

Also, if you are using any silicone hoses, they should use constant-tension hose clamps instead of the usual cheapo clamps.   C-T clamps prevent silicone hose from weeping, especially in cold weather.

John 

[eagle19952]

PRESSURE TEST
4-6 psi won't hurt a radiator but it makes leaks obvious.
need a regulator on access.
i built my own.just stay under the cap pressure.

ps. you can over torque a radiator gasket.
not all grades of radiator tank gaskets are equal

[plyonsMC9]

Thank you all!, I referenced a guide which said 57 ft. lbs. for 1/2" grade 5 bolts.  Head markings look like grade 5.  However, would the torque be different for those radiator bolts due to the seals between the metal?  What guidance would you give for tightening those bolts?  I tried a few and they were definitely loose.  Some were not.

What i've learned to this point from what you all have said is that those bolts are basically holding the tank together - and if they are loose or the seals bad, then I will experience coolant leakage. 

My maintenance manuals don't show exploded views of the radiators so I appreciate all the information.  Much to learn.

Best Regards, Phil

[chessie4905]

Where are these 1\2 inch bolts? You're not referring to the radiator tank bolts are you? They look to be about 5/16 or 3/8 inch diameter.


http://www.almabolt.com/pages/catalog/bolts/tighteningtorque.htm

[bevans6]

57 ft lbs is incorrect for any 1/2" bolt, either shaft diameter or head size.  1/2" head size is 5/16" thread, torque should be around 15 ft lbs, or "nice and tight" with a six inch wrench.

[plyonsMC9]

Thank you!  The heads require a 1/2" socket. 

Perfect information w/ regard to torque and "nice & tight" w/ 6 inch wrench.   

I'll head out & do some snug tightening. 

Is there a pressure test kit which would work well for these radiators?  I did a few searches and uncovered quite a large volume of product.  Just not sure which would fit.

Kind Regards, Phil

[Iceni John]

When I snugged down the nuts of my tanks' bolts, I used a screwdriver-handled 1/2" deep socket. (Mine are 5/16" bolts, and I used new stainless-steel fasteners with lightly-oiled threads and lock washers.)   Using a wrench like that prevents overtightening!   As soon as the gasket began to squeeze out, I stopped.   I used Johnson 235-24 cork gasket tape (the thick green one), and its instructions stress to not overtighten the bolts.

One thing that makes it easy to pressure-test cooling systems to help find leaks is to put a Schrader valve on the surge tank's upper vent hose.   I hope I'll never need to use it.

John

[gumpy]

I'd recommend a sequence of tightening every 3rd bolt working around the tank 3 times to get all of them snug. Then do it again for the final torque. Similar to torquing a wheel. Slow and even.

[Scott & Heather]

Funny, all this talk about torque and method. I literally just tightened all my bolts down using my own arm strength and a normal 6 or 8 inch socket driver and I have zero leaks now (with 13,000 miles on the newly tightened radiators). So agonize over it however you want to, but likely tightening those bolts will solve or slow your issue.


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[eagle19952]

Scott's way works best for me too.
Infact slowwwwly tighten until you think the gasket will compress....

Once it protrudes beyond the core and tank...you have (possibly) ruined the gasket.

You don't want it to extrude.
From that point...the gasket cracks.
the seal in the hole circumference might be 1/4 inch of material.

when i built radiators..i used a 1/4" air ratchet.
tightened to contact
and finished by hand wrench and eye.
ps when i said torque...i didn't mean to imply torque wrench

[plyons]

Ha Ha - Scott - I'm pretty sure Craig knows my lack of mechanical genius.  Remedial and basics, how-to, are always appreciated by me.  My daytime world is completely different than my bus world.  With much to learn.  

I'm being sent out of town soon for company work in a couple of days, so trying to gauge level of effort & what I can get done before leaving.  Juggling day job & runs out to the bus to check/tighten.  Then as soon as I return need to take the bus down to  another location.  Hoping not to be trailing coolant.  

Thank you!, Phil