Robert Engle Posted January 4, 2021 Share Posted January 4, 2021 The cooling system on these early straight eights is quite simple. Water passages in the cylinder head and engine block. Core plugs in the head. Oil water heat exchanger. Water jacket Cover plate on the side of the block. Temperature gauge connection. Distribution tube on top of the head. I did notice on the pictures of the pan and rear main bearing that there was a lot of water corrosion on metal parts. Even engines that have sat for 30 years don't show water corrosion in the lower end of the engine. If I were a betting man, I would put my money on a cracked engine block. I hope I am wrong. Bob Engle Link to comment Share on other sites More sharing options...
Robert Engle Posted January 4, 2021 Share Posted January 4, 2021 The cooling system on these early straight eights is quite simple. Water passages in the cylinder head and engine block. Core plugs in the head. Oil water heat exchanger. Water jacket Cover plate on the side of the block. Temperature gauge connection. Distribution tube on top of the head. I did notice on the pictures of the pan and rear main bearing that there was a lot of water corrosion on metal parts. Even engines that have sat for 30 years don't show water corrosion in the lower end of the engine. If I were a betting man, I would put my money on a cracked engine block. I hope I am wrong. Bob Engle Link to comment Share on other sites More sharing options...
drovak Posted September 24, 2022 Author Share Posted September 24, 2022 A lot has happened in nearly two years since I first discovered coolant in the oil, but in general, I made very little progress on the car until the last few weeks, when I got in gear to try to have it ready for an upcoming local show. My friend helped me resleeve the heat riser assembly. With help from Str8-8-Dave, I was able to remake the linkage for the thermostat assembly. I also rebuilt the mechanical fuel pump and fixed an air leak in the kluge of a fuel pickup the previous owner used in the replacement fuel tank. I got the engine components reassembled enough for a test and found that I had some oil and smoke coming out the exhaust manifold gasket, but this seemed to resolve after some incremental tightening of the nuts. Compression looked very consistent all around. The engine probably had nearly an hour of idling and the occasional throttle blip on it as I was still trying to solve my mixture problem. I've checked for vacuum leaks, fuel delivery, float level, etc., and yet I can still only prevent backfiring by pulling the choke halfway out. But all this is moot, because after my three minute drive to the gas station and back, I noticed that I had milkshake for oil again. No discernable oil in the radiator. Heat exchanger is still strong, and I trust the machine shop did a good job with the head. At this point, I'm thinking I need to investigate the block better. Any tips on locating cracks in the block? Link to comment Share on other sites More sharing options...
Hubert_25-25 Posted September 24, 2022 Share Posted September 24, 2022 Do a leak down test. You can pressurize each cylinder. Listen for air leaking into the exhaust (exhaust valve leak), carburetor (intake valve leak), oil cap (ring leak by), radiator (bubbles - head gasket or block or head leak to locate which cylinder. Hugh https://www.amazon.com/faersi-Cylinder-Leak-Detector-Compression/dp/B07VFG6HCC/ref=sr_1_6?crid=2M2GCQDJ9YH6X&keywords=leak+down+tester+automotive&qid=1664035188&qu=eyJxc2MiOiI0LjIzIiwicXNhIjoiMy40OCIsInFzcCI6IjIuOTYifQ%3D%3D&s=automotive&sprefix=leak%2Cautomotive%2C150&sr=1-6 1 Link to comment Share on other sites More sharing options...
drovak Posted September 24, 2022 Author Share Posted September 24, 2022 I did a normal compression test after I found the milkshake and all cylinders measured about 80 PSI—basically what I measured before the incident. I do have a leak down tester, so I'll give that a go as well. Link to comment Share on other sites More sharing options...
drovak Posted September 24, 2022 Author Share Posted September 24, 2022 Last night, I did try to cap off the coolant side of things and apply a slight vacuum to see if I could detect any leaks. I did not detect any leaks, and it held vacuum for many minutes before I saw a slight drop on the gauge. This doesn't seem very definitive, though. I also cranked the engine over by hand to see if that had any impact, and it did not. I'm wondering if this leak is only really presenting itself when the engine is really warmed up and under load. Again, I didn't have any milkshake for at least an hour of total engine time until I actually drove it to the gas station. I've been running it off and on over the course of seven days. If I have a cracked water jacket, a leak down test could still pass, depending on where the crack is, correct? Link to comment Share on other sites More sharing options...
raydurr Posted September 24, 2022 Share Posted September 24, 2022 To locate the coolant leak I would do the following. Remove oil pan. Remove spark plugs. Fill the block with coolant.Pressurize the coolant portion of the block to 5-10 lbs. After a few minutes rotate the engine by hand.If coolant exits a particular cylinder, then you know where to start. If coolant exits rod, main or camshaft journals then is probably the cooler. Pay close attention to the freeze plugs behind the tappet covers. The leak should reveal itself. Link to comment Share on other sites More sharing options...
drovak Posted September 24, 2022 Author Share Posted September 24, 2022 Good idea. I'll give that a go and report back. Link to comment Share on other sites More sharing options...
drovak Posted October 11, 2022 Author Share Posted October 11, 2022 I installed the oil heat exchanger (upside-down, for ease of installation and to catch any coolant that might leak into the oil side). I proceeded to fill the block with water mixed with some fluorescein sodium salt. I pressurized the system to 10 PSI and saw no signs of leaks, even after rotating the crank. I increased the pressure incrementally up to 35 PSI where I let it sit for the night. When I came back in the morning, I noticed a very tiny amount of fluorescein showing next to one of the head bolts. The blue liquid is WD40, which I had originally sprayed to move the emulsified oil to the oil pan. More in the next post. Link to comment Share on other sites More sharing options...
drovak Posted October 11, 2022 Author Share Posted October 11, 2022 This bolt and hole correspond to one of three that had cracks running to the water jacket. The cylinder head shop noticed this and sleeved the bolt holes with brass. It is perhaps possible that the threads are leaking, but I did use a good amount of PTFE-based thread sealant for each bolt. Maybe this slow leak (with 35 PSI behind it!) turns into a faster leak when the engine is hot. I don't see any signs of leakage from the block, thankfully. Any thoughts as to where to go from here? I assume finding a new head will potentially present itself with the same three cracks, so repair seems like the best option to me. If so, who should I take this to, and how best should it be repaired? Link to comment Share on other sites More sharing options...
EmTee Posted October 11, 2022 Share Posted October 11, 2022 This is a non-pressurized cooling system, correct? The size of the leak at 35 psi would seem to indicate that under normal operational conditions the engine should be OK. Link to comment Share on other sites More sharing options...
drovak Posted October 11, 2022 Author Share Posted October 11, 2022 It is indeed non-pressurized. I would love to think that this is a non-issue, but given I've gotten significant amounts of coolant in my oil on two separate occasions, I clearly have a problem. The head bolts are indicating a problem, however small. Unfortunately, it is hard to say for sure if this is *the* problem. Link to comment Share on other sites More sharing options...
EmTee Posted October 12, 2022 Share Posted October 12, 2022 15 hours ago, drovak said: It is perhaps possible that the threads are leaking, but I did use a good amount of PTFE-based thread sealant for each bolt. I presume that included this bolt: I would consider draining coolant and removing that bolt and inspecting the threads. Maybe the bolt or the block threads are worn (or pitted) and allowing some coolant to weep despite the sealant. Try to dry the hole with compressed air then reseal the threads, reinstall, re-torque and repeat the pressure test at lower pressure (maybe 15~20 psi max.) for a longer duration (e.g., 24 hours) to see whether the leak reappears. Link to comment Share on other sites More sharing options...
Matt Harwood Posted October 12, 2022 Share Posted October 12, 2022 I would look closely at the oil cooler. For you to have that much coolant in the oil is far more than seepage past threads on a head bolt. Ancient oil coolers are notorious for leaking and failure, which is why so many of them are bypassed. My Lincoln has a similar cooler in its cooling system and I was warned by several experts to get rid of it and bypass it. A small leak there can create all kinds of mischief. I have this bypass for my Lincoln now: On the other hand, with the oil pressurized and the coolant not pressurized, I'm surprised coolant ended up in the oil instead of the other way around. Are you sure that wasn't due to the 35 PSI test? Are there perhaps ports on the block/head that are being blocked by the head gasket? Is your water pump working correctly and not being too aggressive? Does your radiator flow properly? Unpressurized coolant shouldn't be able to push into pressurized oil passages, certainly not in any volume. That's what makes me come back to the oil cooler. 4 Link to comment Share on other sites More sharing options...
drovak Posted October 12, 2022 Author Share Posted October 12, 2022 I found that the oil cooler did indeed have coolant in the oil side after the pressure test. I thought I had adequately repaired it before when I found a pinhole leak, but apparently not. I will bypass it once and for all, and will assume the head is fine until proven otherwise. I'm thinking the oil cooler had a slow enough leak such that water was accumulating at the bottom of the oil pan the entire time. It was only when the car was driven that caused the water to slosh around and find its way into the oil pickup. 1 Link to comment Share on other sites More sharing options...
raydurr Posted October 12, 2022 Share Posted October 12, 2022 I would definitely permanently bypass the oil cooler. A completely filled and pressurized cooling system should reveal a substantial leak soon . I have even left pressurized overnight. Link to comment Share on other sites More sharing options...
drovak Posted October 12, 2022 Author Share Posted October 12, 2022 For folks that have permanently bypassed the oil cooler, what parts did you buy? The brass and copper connections made between the block and the oil cooler were not original on my car, so I'm fine putting something else in its place. The 3/8" FIP threads on the block look good, but show a lot of corrosion immediately below them. What's the best way to address this? Link to comment Share on other sites More sharing options...
Str8-8-Dave Posted October 12, 2022 Share Posted October 12, 2022 So under normal running circumstances a leaking oil cooler would leak oil into the water jacket which would cause a sludge to appear in the radiator, not anti-freeze coolant into the oil. The oil pump supplies 20-35 psi to the oil side of the cooler and coolant pressure in the surrounding housing is 0 psi, the cooling system is non-pressurized, it's open to atmosphere at the overflow tube in the radiator neck. Artificially pressurizing the cooling system to 35psi may actually create a leak. 1 1 Link to comment Share on other sites More sharing options...
EmTee Posted October 13, 2022 Share Posted October 13, 2022 1 hour ago, Str8-8-Dave said: So under normal running circumstances a leaking oil cooler would leak oil into the water jacket which would cause a sludge to appear in the radiator, not anti-freeze coolant into the oil. What happens when the car is cold and sits? Coolant is heavier than oil, so is it possible for the water/glycol to migrate into the oil passage when the engine is not running? I suppose this may depend upon the physical configuration of the cooler and the location of the leak... Link to comment Share on other sites More sharing options...
drovak Posted October 13, 2022 Author Share Posted October 13, 2022 Now I'm really confused. I submerged the oil cooler in water, and pressurized the oil side to 30 PSI. No bubbles visible. Given the amount of coolant (maybe 20 mL; wish I had measured...) that poured out after my coolant pressure test, I am really back to wondering if this is the main culprit. And why can't I get it to bubble if there really is a leak? I still plan to find the parts to bypass it (if someone has some suggestions for fittings that work with the holes in the oil cooler housing, that would be appreciated), but am still scratching my head why I'm accumulating as much water as I am in the oil, with no substantial trace of oil in the water. Link to comment Share on other sites More sharing options...
drovak Posted October 13, 2022 Author Share Posted October 13, 2022 Given the oil cooler has a bypass valve, is it possible to simply plug the two oil connections on the block, or is this not advisable? Link to comment Share on other sites More sharing options...
drovak Posted October 13, 2022 Author Share Posted October 13, 2022 I sealed off the oil inlet and outlet holes in the oil heat exchanger with some washers, gaskets, and #2 sealant for good measure. Someday, I'll get creative and bypass the oil cooler internally instead of externally, but this will do for now. I plan to simply cap off the oil inlet and outlet holes in the block unless someone suggests otherwise. Given there is a good path inside the oil pump for oil to flow, this doesn't seem like it would limit the flow rate substantially. I removed the oil pump to examine the state of the bypass and relief valves. The relief valve is free moving and is presumably in working order, given I have good oil pressure. The bypass valve was completely and utterly stuck in the not bypassed position. The spring is broken in two pieces, and after finally extracting the piston, it was corroded, but not too badly. It could be serviceable after finding a replacement spring, but for now, I'm leaving it out with the thought that it will not contribute anything to the functionality given I'm permanently bypassing the oil heat exchanger. Link to comment Share on other sites More sharing options...
drovak Posted October 13, 2022 Author Share Posted October 13, 2022 Here's the piston cleaned up some. While I was removing the oil pump, I noticed the brass tubing going towards the front of the engine was somewhat crimped. I also noticed a cracked solder joint. Is this severe enough to warrant removing and repairing it? Link to comment Share on other sites More sharing options...
EmTee Posted October 13, 2022 Share Posted October 13, 2022 3 hours ago, drovak said: Is this severe enough to warrant removing and repairing it? I certainly would! It sure looks like that line was abused by some ham-fisted 'mechanic' at some point in the car's history. That cooler bypass piston sure looks like it has seen better days. Maybe @dibarlaw has suggestions for sourcing a replacement spring... Link to comment Share on other sites More sharing options...
Dave39MD Posted October 13, 2022 Share Posted October 13, 2022 This is what the by pass on my 31 oil warmer looks like. It was done by the previous owner. Dave Link to comment Share on other sites More sharing options...
EmTee Posted October 14, 2022 Share Posted October 14, 2022 Hmmm, where is the green drip in the photo above coming from? Link to comment Share on other sites More sharing options...
Dave39MD Posted October 15, 2022 Share Posted October 15, 2022 A previous owner whittled a couple of wooden plugs for the oil line in and outs which let the coolant seep out. That repair is odd since they did a good job on the by pass line. Dave Link to comment Share on other sites More sharing options...
drovak Posted October 16, 2022 Author Share Posted October 16, 2022 Gotta love McMaster's lightning fast delivery when living near a distribution center. Ordered parts Friday, and UPS dropped it off Saturday. I bought two 3/8 nominal (1/2" ID) 90 degree elbows and 3/8 nominal (1/2" OD) copper pipe, type L (as they didn't have M in stock). I cut two sections of 1.25" pipe for the vertical pieces, and one piece 1.96" long for the horizontal. I sweat fit the elbows to the vertical pieces first. Then, I installed them in place with two 3/8" MIP to 3/8 nominal (1/2" OD) compression fittings, and installed the horizontal piece with some flux. I snugged the fittings up until the vertical pieces just barely wouldn't move, and found that the horizontal piece was fairly secure in place. I wasn't brave enough to sweat this in place, though with some fiberglass (or asbestos, of course), perhaps you could adequately protect the engine paint. Instead, I carefully removed the assembly and sweat fit it on the workbench. After cleaning the flux off and reinstalling it, I found that it fit perfectly. McMaster part numbers are 5520K78 for the elbows and 5175K122 for the pipe. The compression fittings were purchased at Home Depot. Home Depot doesn't seem to carry anything smaller than 1/2 nominal (5/8" copper) water pipe, though you can find copper tubing in smaller sizes. 4 Link to comment Share on other sites More sharing options...
DonMicheletti Posted October 16, 2022 Share Posted October 16, 2022 I find Mc Masters great, and, like you, find their delivery quick. Also, having it dropped on your doorstep beats running around trying to find things that are difficult to find. While they are not cheap, you can get stuff you can't find (easily) anywhere else. 3 Link to comment Share on other sites More sharing options...
Matt Harwood Posted October 16, 2022 Share Posted October 16, 2022 I have a McMaster distribution center within a 10 minute drive of my shop. It's insane how often I'm there... 1 Link to comment Share on other sites More sharing options...
Mark Shaw Posted October 17, 2022 Share Posted October 17, 2022 I suggest you first check your freeze plugs for leaks. Link to comment Share on other sites More sharing options...
drovak Posted October 17, 2022 Author Share Posted October 17, 2022 Mark, where are these freeze plugs you refer to? Bob mentioned that there aren't any plugs on the early straight-8s as there is a side water jacket cover to remove the casting sand, and hence, no need for smaller plugs. Other than the head, I'm not seeing any other plugs on my engine. Link to comment Share on other sites More sharing options...
Pete K. Posted October 17, 2022 Share Posted October 17, 2022 Dear Drovak, check your block very closely by removing the front valve cover plate, where the water jacket curves under towards the cylinder walls, old Buick's seem to have a very thin casting area that is prone to a longitudinal crack at that spot. Happened to me years ago on a '30 6 cyl. block. Not so sure on the '31, but I'd surely check it out anyway. Link to comment Share on other sites More sharing options...
drovak Posted October 17, 2022 Author Share Posted October 17, 2022 2 hours ago, Pete K. said: front valve cover plate Are you talking about the front plate covering the push rods and tappets? I'm not seeing any sign of cracks or corrosion anywhere near there. When I had the push rods and tappets out before, I didn't detect any cracks either. Link to comment Share on other sites More sharing options...
drovak Posted October 18, 2022 Author Share Posted October 18, 2022 I pulled the water manifold and rocker arms tonight to give the head a tightening. The head bolts are at 70 lb-ft now. Quite annoying, having to take off the manifold and rockers to retorque the head. Upon taking off the water manifold, I discovered the gaskets are good for only one use. Would these have been copper originally? Guess I'll be ordering some more shortly. Link to comment Share on other sites More sharing options...
EmTee Posted October 18, 2022 Share Posted October 18, 2022 That looks like an exhaust gasket to me, since it has that steel core. If that's a coolant flange you should be able to make one from a sheet of fiber gasket material. I still have most of a sheet that I bought at NAPA and used to make gaskets for my '38 when I removed the water pump and thermostat housing last winter. Link to comment Share on other sites More sharing options...
drovak Posted October 18, 2022 Author Share Posted October 18, 2022 3 hours ago, EmTee said: That looks like an exhaust gasket to me, since it has that steel core. Olson's (where all of my gaskets came from) appear to use the same material for the oil feed gaskets, water manifold, and probably others that I'm currently forgetting. I will cut six new fiber washers and use those instead. 1 Link to comment Share on other sites More sharing options...
DonMicheletti Posted October 18, 2022 Share Posted October 18, 2022 The water passage gasket was probably cork originally. Any gasket material easily compliant 1 Link to comment Share on other sites More sharing options...
Pete K. Posted October 20, 2022 Share Posted October 20, 2022 Yes, you nailed the spot in your great photo. I was told to check for cracks there, by older mechanics that worked on the old Buicks when still being used everyday. Again, This was a 1930, 6 cyl. block I had.. Very possible Buick thickened up that area for the '31's. Link to comment Share on other sites More sharing options...
drovak Posted October 22, 2022 Author Share Posted October 22, 2022 I am happy to report that after retorquing the head and completely bypassing the heat exchanger, I no longer have oil and coolant mixing. She was running just in the nick of time to take to the car show this morning. Now I have to figure out why the gas pedal sticks down a bit, get a better rear view mirror, find some new flowers for the bud vase, and other high priority items. Many thanks to all who have helped with excellent suggestions and wisdom along the way. I'm very grateful for this community! 5 Link to comment Share on other sites More sharing options...
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