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#1
08-12-2021, 12:04 PM
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Curious to know if there is any external oil or coolant leakage at the HG under the vacuum pump area. Overheat/HG problem often leads to external leaks in this area. Maybe not enough time run to verify leakage but it could be a sign.
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1985 744 gle d24t 1985 745 gle d24t 
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#2
08-12-2021, 10:52 PM
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Yeah I70 is shut down for days no. Wildfires from last year = no vegetation to stop soil from creating mudslides. It's been a goat roping, traffic re-routed on 4+ hour detours through mountain towns. Should be open in the next couple days tho!
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#3
08-13-2021, 09:31 AM
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That's right I read about that closure too, forgot that. Crazy!
As for the mechanic's next steps, the biggest advice would be to just make sure he doesn't make the problem worse than it already is by making any unforced errors. Think through the potential consequences carefully on any diagnostic steps, such as that pressure test which was a risky move if the engine was started afterwards without removing glow plugs or injectors to clear cylinders first, assuming that was not done. Remember this is a diesel engine. The compression ratio is over 20:1 so you cannot tolerate ANY quantity of liquid in the combustion chamber or it will cause instant catastrophic damage as soon as the starter is engaged. The biggest risks to avoid are hydraulic lock (can occur if coolant from a failed headgasket enters cylinders) and contamination of the engine OIL with coolant. This is the reverse of what you have seen so far -- oil in the coolant -- but if it's going one direction it can often also go the other through the same interface point. Glycol in the coolant damages engine bearings, meaning the damage would spread to repairs to the bottom end of the engine also. I would recommend sending an engine oil sample drained off the bottom of the sump after sitting overnight to a lab for analysis to have them check for presence of glycol in the oil. If there is any, DON'T run the engine with it in there, dye or not. I am not clear on what the dye is intended to accomplish. Since the leak you are searching for is internal, the dye will obviously go everywhere the oil goes regardless of the source it's originating from. Maybe we are missing something on that? Or is he searching an external leak? Your goal now is to limit the repairs to replacement of the headgasket or whatever failed -- not other things that suffered collateral harm! The more limited the repairs the faster you will be able to get your truck back on the road, particularly if you can avoid having to haul the entire engine out As for the reason for the failure -- keep in mind you will want to devote some time to figuring out WHY this happened in the first place, rather than just reassembling after you find the point of failure and then assuming it won't happen again. If the root cause is still there, it will happen again, probably as soon as you attempt another trip where the engine has to work hard. Remember no amount of new parts will guarantee a reliable engine if the engine is sabotaged during assembly.
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86 745 D24T/ZF 345k lifted 2.5" 83 764 D24T/M46 155k
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#4
08-13-2021, 11:13 AM
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Very good, very methodical, very detailed explanation.
Yes so maybe we can find out more about what went into this HG R/R. What was the surface preparation? Was it sufficient for the HG type (fiber or MLS)? Some experienced D24T-ers swear by a very light misting of Hylomar spray dusting on both sides of the HG. Was the cylinder head checked for excessive warping or twist? What type of fasteners? Original type triple-square screws, or studs? New or reused? How tightened? In stages? What torque levels? Beam or clicker wrench? (as v8volvo mentioned above). Re-torqued after 1,000 miles? Also-- We should not categorically rule out the possibility of a defective oil cooler, even a new one. Although the symptoms do appear to be more consistent with HG failure, as stated above.
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1985 744 gle d24t 1985 745 gle d24t
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#5
08-14-2021, 08:30 AM
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The fact that the OP said the hose blew *after* the engine overheated suggests this theory would be off the mark, to my thinking at least, but then again, in the heat of the moment (no pun intended  ) with many things happening at once plus trying to navigate traffic it can be hard to recall exactly afterwards what happened and how/when/what order. We all have been there. If the real sequence was that the hose blew first, or at least began to leak coolant out, then oil cooler failure could be the cause. Oil cooler failure is not statistically common -- identical cooler used in millions upon millions of VW/Audi/etc vehicles worldwide from '70s to recent -- so we'd know if they were a trouble spot and probably a majority of those that do get replaced are wishful attempts where a head gasket problem is the real issue -- but infant mortality/DOA with new parts does happen, especially aftermarket. Headgasket failure OTOH is statistically common in engines where provoked by lack of due care paid to the preventive measures esp when combined with extreme operating conditions. No reason to rule out the possibility though, pending further diagnostics steps, agree for sure. Sethsquatch can you remember when was the last time you had checked coolant level/appearance prior to this breakdown? Is there a possibility oil had been present in the coolant for some number of days/weeks beforehand?
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86 745 D24T/ZF 345k lifted 2.5" 83 764 D24T/M46 155k
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#6
08-14-2021, 11:06 AM
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Made me to think oil cooler failure was a thing. But it appears to be an urban legend based on wishful fantasies (anything but admit to a HG problem).
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1985 744 gle d24t 1985 745 gle d24t
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#7
08-15-2021, 08:26 AM
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None of these models are known for common oil cooler problems. They can fail and presumably do, sure. But not often. I used to see dozens of TDI cars come through a shop every week, plus other Volvos and VW diesels using this part, many reaching 250k, 300k, 400k plus mile ranges. Never saw a failed cooler -- not one single failure. If they had any kind of tendency to fail, the much more common applications like TDI would have enthusiast owners buzzing with the need to watch for it, and the whole world would be aware that 25+ years worth of incredibly diverse VAG products ranging from ancient beater Rabbits to shiny late model Audis to commercial and military trucks have an oil cooler that needs attention paid. A pandemic of oil cooler failures across a colossal global population. None of that is seen. Hence my skeptical opinion that it makes no sense this extreme low volume US Volvo D24T application would see hardly any failures at all, let a lone a high rate, and my guess that it is simple optimism or denial when people replace that cooler (or seek to eliminate it) after overheating their engine and finding oil in coolant afterwards....Last of all, the use of one part in so many applications and with zero revisions across 3 decades is a pretty good vote of confidence from the OEM, who doesn't want to pay warranty repairs any more than we don't want to replace them all these years later, and uses failure rate data to make their decision. All this simply to say to the OP (and whoever reading in the future with oil in coolant!), IMHO best not get your hopes up for an oil cooler failure, although certainly checking for it is always a smart idea in the interest of complete diagnosis. If you want to conclusively test the oil cooler for oil/coolant barrier leakage, you can easily disconnect the hoses and pressure test it in isolation from the rest of the engine.  Either from the coolant side using a pressure tester, or by running the engine with coolant hoses disconnected at the cooler and see if it flows pressurized oil out the coolant hose connections. This process rather than dye in the oil would rule the oil cooler out.AUDI 100 1992-1994 AUDI 4000 1982-1983 AUDI 80 1988-1990 AUDI 90 1988 AUDI A4 1997-2001 AUDI CABRIOLET 1994 VOLKSWAGEN BEETLE 1998-2006 VOLKSWAGEN CABRIO 1995-2002 VOLKSWAGEN CORRADO 1990-1992 VOLKSWAGEN EUROVAN 1993-2003 VOLKSWAGEN GOLF 1998-2003 VOLKSWAGEN JETTA 1981-2005 VOLKSWAGEN PASSAT 1993-1999 VOLKSWAGEN QUANTUM 1982-1985 VOLKSWAGEN RABBIT 1981-1984 VOLKSWAGEN RABBIT PICKUP 1981-1983 VOLKSWAGEN SCIROCCO 1984-1989 VOLVO 740 1985-1986 VOLVO 745 1985 VOLVO 760 1983-1985 https://www.fcpeuro.com/products/aud...17021b#fitment
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86 745 D24T/ZF 345k lifted 2.5" 83 764 D24T/M46 155k
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