exhaust gases in coolant--any help please? - Defender Source
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Old April 23rd, 2005, 09:22 PM
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Chris Davis
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exhaust gases in coolant--any help please?

Well, here I go again. Still have the coolant blowing out the resevoir and still have exhaust gasses in my coolant. I re did the head gaskets (and thoroughly inspected them for any leakage which I could not see) and it is still having the issue. I am thinking dropped cylinder or porous block, which means my 4.6 is toast. I am hoping there is a third possibility that I have overlooked that one of you may. I am at my wits ends and I am not sure what I can do--I think I need to build another engine. Please help if you have some ideas, I am literally stressed on this to the nth degree.

thanks,

Chris
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Old April 23rd, 2005, 10:20 PM
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Well, first thing I would consider. How does the truck run? Even figuring the worst situation of a dropped cylinder, is the truck drivable? If that's the case, and the block is a dead cause anyways, then don't be so concerned about what happens to it. Just drive it. I mean, whats the worst that can happen? Drop a cylinder?

Should you have to build a new engine, I remember reading on the Rover V8 forums that the 4.0 and 4.6 share the same block and only the crank, rods and pistons were different. Your 4.6 is the serpentine belt type, correct? Or you can give a ring over to D&D Engines (www.aluminumv8.com) and have him build you a nice 4.8 stroker out of a 3.9 block and e-bay the rotating assembly from the 4.6 to help offset the costs.

But I wouldn't give up on the current beast just yet. I'd have a good shop run both a compression and leakdown test on all 8 cylinders. This should show a cracked or porous block. If you had dropped a sleeve, you would have been able to see it while you had the heads off, so I doubt that would be it.

-Hans
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Old April 23rd, 2005, 10:35 PM
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Chris Davis
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Mine is v-belt since I built the 4.6 using a 4.0 used block and reused all the other components from the 3.9 of my 94. I don't want someone else to build the engine for me, but I appreciate the lead on D&D. I have aleady run a compression test, but not the leakdown test. I am not exactly sure what a leakdown test is, but if it is pressurizing the coolant system and checking for water in the cylinders, then yeah, I have done that too. The truck is running good, but I don't want to warp my heads--which would be bad. How can you see the dropped sleeve? I checked for indents in the gaskets and did not see anything such as a gap, but I don't really know what to look for. Could you point me in the right direction? I have the ability and most the tools to check just about anything but I have already done everything I can think of.

And please don't anyone suggest getting a diesel! I already want one but I flat out can't afford it. Since I do my own labor, I can redo my engine for the cost of fluids, gaskets and a spare block, but can't dish out $5k for a diesel (oh, if only there was a way!).
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Old April 24th, 2005, 12:00 AM
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A leakdown test is similar to a compression test, but not quite. It uses an outside air source to pressurise the cylinder using an adapter in the spark plug hole. Then, you time how long it takes for the pressure to bleed out of the cylinder. The compression test figures out if the cylinders are developing pressure, the leakdown test looks to see if they can hold it. Like a compression test, it's done individually in every cylinder, and you are looking for variations between them and has it's own type of gauge to do it. If you had a hole in a cylinder, it would bleed out the pressure faster in that cylinder than the others. In theory it should indicate if you have a cylinder suffering from porosity or a crack.

If you dropped a sleeve, normally you would see it physically sitting lower in the cylinder. Instead of the sleeve being flush with the top of the head, you would see a "step" at the top of the block where the sleeve had sunken down.

Another item I just thought of here. No matter how well you drain the coolant system from the radiator, you will still have some coolant inside the water jacket of the block (a few quarts at that!) You might still be picking up the traces of the exhaust in the old coolant from the problem in the past if you didn't flush out the old stuff. I say give it a really lengthy flushing to get all the old coolant out as much as possible to eliminate that possibility, then re-test it.

As to blowing the coolant out of the overflow tank, if it does it once or twice after flushing and filling, it might just be from purging the air out of the system. If you have an air bubble trapped in there somewhere, when it expands it will force out some coolant. But after a couple heat cycles, it should clear out of there if you burped out the system well.

And I totally understand wanting to build the engine yourself. Not everybody can do it, but I love doing it too.

-Hans

Follow-up Post:

Oh, I forgot to ask. Which type of headgaskets did you use? Composite or Tin?

-Hans
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Old April 24th, 2005, 10:59 AM
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I used composite gaskets. I fully flushed the system under pressure through the heater hoses and then retested the system with the block tester when the engine was first built and run and did not have a problem. It was after fully freeway testing it that I noticed the higher pressure in the system (cap was hissing and low on coolant) that I then retested it and found the exhaust gasses, so I think I ruled those out but again I have not had definitive evidence of any one problem so I am not about to scrap the block till I figure out exactly what the cause is. I just don't like treating symtoms.

I will have the leakdown test done and see what comes of it.

Thanks for the suggestions--any more are completely welcome!

Best regards,
C
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Old April 24th, 2005, 02:02 PM
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Davis, what head gasket was in your engine when you tore it down? Perhaps there is a head bolt issue. [unless you purchesed new for the comp gasket]
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Old April 24th, 2005, 05:06 PM
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Both when I built the engine and subsequently changing the head gaskets, I used composite gaskets and both times used new head bolts. I inspected with a magnifying glass the old head gasket as well as the block and the head for any tell-tale blow buy marks but found nothing.

Today I purchased some liquid glass block sealant and since it is going to require some diligent flushing of the radiator, I may have to leave it for a future week (I need to play for a while before working on the truck and get some good Juju feelings flowing for extra luck). I have heard some good things about it for leaks such as mine and I am not relishing pulling the engine again as I have other projects to move on to. As soon as I run it, I will post what I find.
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Old April 24th, 2005, 10:51 PM
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I've also heard some good things about the block sealant stuff. If it's a cracked block or something of that nature, it should hopefully cure the problem. Maybe not permanently, but at least for a while.

Another thing too. When I did my headgaskets, I also THOUGHT everything was purged out and done after some easy driving around the block. It all seemed ready to run and I merrily drove off to work. That first trip down the highway, it was overheating and hissing and puking coolant out the tank on mine too. (remember the thread "runs like dog poop"?). I refilled the overflow tank, adjusted the timing, and next trip it did it again but much less. I refilled the tank again and now, the only time my heat gauge goes up is for about 5-10 seconds when the thermostat first opens and all the hot water from down in the bottom of the block passes by the sender. It comes back down right away, and I can cruise along for hours now. I talked to a few other folks about it, and apparently the top-end of most engines gets a bit of a temp spike when the thermostat opens since the thermostat is the furthest and last part to warm up.

But you need to get the engine up to operating temperature to fully purge out the cooling system. Until you get it up to to 190, you don't get any expansion of the air bubbles as well as not getting any flow past the thermostat into the radiator to actually push them out of the system. And as much as we complain about overheating problems, these engines really stay pretty cool when you aren't pushing them if everything is working properly. You need to run it out and get the temp and pressure up to fully purge the system. When that happens, and if you have a lot of air in the system like ours can get, it's going to act like a pent up volcano the same way you described.

Also. Maybe replace the radiator cap too? It's a cheap part, but if it's opening at too low a pressure, then you're going to get boiling and all that good stuff.

-Hans
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Old April 25th, 2005, 11:51 PM
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I hear ya--but I am not overheating, so I don't think it is a pressure thing. I am blowing out coolant and, using a block tester, am showing exhaust gasses in the coolant. I fully purged my old coolant, removing both block bolts and running water through everything.

Tonight I repurged my system and added K and W block sealant. Followed directions to the "T" and am letting sit for a couple days. I will give updates on this as it warrant--I am curious if block sealant is BS or not.....
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