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Discussion Starter · #1 ·
Hey guys, havent posted in a long while. Im at my wits end with this coolant leak. Quick back story. Have owned truck since '06 about 10 years ago I developed a small coolant leak (adding water every few months). Started to get pressure in upper rad hose. All the mechanics said its a HG, so 8 yrs to date I ripped apart motor replaced HG with "C" gasket used ARP studs, replaced injectors and all supporting parts ie: lines, hardware etc. When I had a machine shop do the heads injector cups were all seated properly and they advised not to mess with them. For the past 8 years its been doing the same thing, having to add water every couple of months. Now its getting worse if I drive more than an hour or so "low coolant" shows. I still get a crazy amount of pressure in system after it has cooled down (next a.m.). I have done combustion gas test on the rad reservoir, shows negative. Reservoir is clean as a whistle, no black soot or anything to indicate combustion gases in system. I have tried all the common things, replacing cap with oem cap, pressure test leaks down 1 psi in the 5 min test, but holds that pressure if left longer. Okay so that might not have been a "quick" back story, but either way, Im at a loss of what to do next. Is it possible I need to pull apart and do injector cups? At this point Im 100% certain it isnt the HG. Any thoughts would be appreciated. Thanks for what you guys do!
 

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Discussion Starter · #2 ·
Also, I replace water pump, thermostats when HG was done. I have already checked the block plate on passenger side rear of motor. Ive checked everywhere as far as hoses and problems spots that Ive heard of.
 

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2007 Klassic CCSB 2500HD. Six-gun w/speedloader, iDash, and EFILive.
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Have you thought about pressure testing the cylinders to localize/verify the problem?

There are a lot of weird one-off things that could happen. Like unicorn weird, but as my good buddy says, once you eliminate the impossible...

If you think it's exhaust gas blowing coolant out via the recovery tank, you should be able to verify that by taking a plastic soda bottle, inserting the recovery tank overflow tube, securing it to the vehicle, and then driving for a while.

Any chance it's a Kali emissions truck? you could have an EGR failure where it's leaking coolant into the intake. That would be one in a million.

I know you said you've checked everywhere, but what about the heater core and tubing? I'm guessing if it was leaking you'd notice the wet carpet and smell in the cabin.

Have you had the oil tested at a lab for coolant contamination? There is an oil/coolant heat exchanger.

I'm assuming that if the coolant was breaching the coolant/transmission fluid heat exchanger you'd have noticed the Pepto-bismol colored tranny fluid by now.

Was the machine shop that did the heads/studs/gaskets able to confirm a failed HG? There's almost always evidence.

In any case, your coolant is going somewhere. We just don't know where. Best we figure that out first. Coolant dye and a blacklight might be in order as well. First....try that overflow catch-bottle hack.

~Roz
 

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Discussion Starter · #4 ·
Thanks Roz for the time.

By pressure testing cylinders do you mean the standard radiator pressure test? Im not familiar with just pressurizing cylinders, I will research.

I don't think exhaust gas in coolant. Have done the combustion fluid test and was negative. Reservoir is clean (no black soot) fluid is very clean no milky look to it.
No emissions on truck.

Heater core doesnt appear to be leaking.

I have not yet had the oil tested but it is very clean, but then again I run amsoil with bypass filter so it usually stays pretty clean

I cant confirm machine shop saw evidence of faulty HG, it was nearly 8 or so years ago. The machine shop is a reputable shop around here, so I assume they did a good job. Either way I have been running for this long with now issue other than the leak.

I did talk to a Diesel shop today and he mentioned since I didnt true the block when I did the job that could possible be the issue, but I took alot of time cleaning and making sure it was smooth, but then again I guess I wouldnt be able to see minor imperfections.
 

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Discussion Starter · #5 ·
I added a radiator bypass filter. Learned how to on this board. Basically "T"ing off heater core lines and running to a filter. After pressure testing radiator I found a small leak at the plastic T fitting I used. So yesterday I took off filter and replaced heater core hoses. I dont think this will be the issue, but we'll see. One question I have, If I have a leak in a rubber line will that create pressure in the system? Theoretically if coolant gets low then turns to steam I guess this would create pressure?
 

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2007 Klassic CCSB 2500HD. Six-gun w/speedloader, iDash, and EFILive.
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Hi. Sorry, been a bit busy. I disagree with your mech on needing to deck or 'true' the block. My dad had a rotary broach and made good money decking blocks for race cars, but ... that's what it's for. high-performance high-rpm applications where you need every cylinder to have the exact same displacement and therefore the same impulse. Step 3 after balancing and blueprinting. Your machinists would have caught it and gladly sold you that service if you needed it. You normally only get a warped block by overheating the hell out of it.

WRT pressure testing the cylinders, it's properly called a compression test. The glow plugs are removed, a gauge on a hose is threaded in, and you crank the motor. It'll generate pressure as part of the compression process, and there are reference numbers which one can use to see how good or poor the compression is on the cylinders. If you have one that's substantially off, it's a good indication that something is amiss. I would urge you to have a proper shop do this because glow plugs can swell up and if you're not careful you can brake parts off in the cylinder. That's bad. Berry Berry Bad.

Air bubbles like to park in heater cores, and if you don't purge the block correctly after you change coolant (or say...have a leak) they can stay stuck in there. And we all know what happens to a gas when you heat it. But I doubt this would cause you to get a low coolant light in an hour if anything it would push coolant back into the tank and then take it back when it cooled off.

I'm not super sold on the tests for exhaust in coolant. The DIY one I had was inconclusive at best. But that's me.

You can get on the Amsoil website and order oil testing kits. In fact, if you're running dual-bypass on an LB7 and changing the oil, you should punch yourself (IMO). Throw a Fumoto drain valve in the pan, fill with 100% synthetic and then send a sample to the lab every 7-10k and keep the oil. There are tons of studies. We do it with aircraft all over the world. The sample/test will tell you things about the motor that may have otherwise been masked. I ran my last oil to about 80k, then honestly changed it out of ....maintenance boredom. The lab said it was just fine.

So....you're losing coolant and there's a crazy amount of pressure in the system. Well, that's because the engine is pressurizing the cooling system I'd say. And for reference, I had an HG issue and never got any indication in the recovery tank. You in fact have a coolant filter on there too, so that could only help make it cleaner.

I would as a normal matter of course switch to testing the oil, and see what's in the first sample. I'd do a compression test and see which cylinder it is. Then you only have to worry about 1 side. The odds it's an injector cup but I don't know of a way to differentiate. If you want to pull and reseal all the cups, then you can skip the compression test. I myself like to know. I prefer to have good data both positive and negative. Absence of proof ain't proof of absence. Roz would be doing before and after pressure testing of the suspect cylinder.

Have you pulled the oil cap off when it's cold to see if there's any condensation up inside the cap? That's a tell. Any smoke when it starts or when it's idling?

Honestly I'm a little surprised that the place that did the HG work didn't pull/clean/reinstall/seal, the cups to start with. It's kind of a thing.

Read what the Ferm says here Injector Cup Sealant Question - Which Loctite????

That's all I can think of. Except I didn't see the part where you put a soda bottle on the coolant overflow hose like I suggested. I musta misread it... (we need to confirm the coolant is venting overboard. This is easy, and free. In fact, you could skip the lab test for coolant in oil. But you're going to have it tested regularly anyway riiiiiiiight?)

Semper Fidelis,

Roswell
 

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Discussion Starter · #7 ·
So I had my local mechanic put pressure on the coolant system, as I have done it before and found nothing. He advised he ran it up to 25 psi, which sounds high. Now I have a visible leak. I would assume running this much pressure probably created this leak. Any thoughts? He said leak was coming at the bypass filter I added so I deleted it and put new hoses with new quick connects. The other leak I am now finding is just in front of driver side motor mount behind coolant tube and exhaust manifold. If HG is leaking, I would assume it can leak out and not in. I did by the way put a water bottle on overflow tube, have not driven yet.
 

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2007 Klassic CCSB 2500HD. Six-gun w/speedloader, iDash, and EFILive.
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If memory serves that cap is a 15 psi cap, so yeah it is a bit more, but who's to say it wasn't leaking at 18?

It would be cool if there was a replacement cap that had a gauge on it so you could see exactly what the pressure was when it was warmed up. Of course, you could probably accomplish the same thing just by leaving your tester connected. If that cap is not functioning correctly it's going to hold way more pressure than it should, which could have forced that leak in the past. Time will tell. If you're really motivated you could get a spare coolant tank from a salvage yard, plumb it for a gauge and your pressure tester, and then see when the cap releases.

Have you left the cap off the tank and let the truck warm up until the thermostats open? You'll have to probably block the radiator off or just wait for a while, but if you have an internal head gasket leak bubbles will make their way to the recovery tank.

Yes, I had gasket can leak externally, or internally.

This may help.
 
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