I have a 1967 Lesabre 400 Custom convertible with the 340-4 and the 400 ST. The engine shows a couple of symptoms and I try to figure out if there are several causes for them or just a single big one. Coolant disappears black fluid coming out of muffler high fuel consumption, stumble in accelaration, high idle I drained and refilled the coolant last year completely and topped it off twice since (I only drove like 100 mls since, if ever). I know there is some seepage, probably from the water pump gasket but also from the intake gasket at the pass. side back of the engine, as I see traces of running fluid in those areas. I have what I believe is a full set of gaskets minus the head gaskets and plan to change them soon. However, I am suspicious I might have a blown head gasket or worse, a cracked block or head, making the coolant level drop. How can I eliminate the doubt? Whenever I start the vehicle I get a big black wet spot in my driveway or on the garage floor. Fluid is dripping out of the end tip of my muffler. I seriously doubt (if not to say rule out) the possibility of condensate accumulating in the muffler as this would rather be clear or rusty brown. It does not smell or taste like gasoline but rather like exhaust gases and/or incomplete combustion. I suspect this might be coolant, either from a busted intake seal, head gasket or, worse, crack in block or head. How can I proof what this fluid is and trace the source? The throttle shaft in my AFB was seized and I overhauled and sonic cleaned the carb over the winter. I changed out a lot of stuff that came with the kit, mainly all gaskets and the accelarator pump. I kept the jets in place and I didn´t mess with the metering rods. I also left the two adjusting screws inthe front untouched (yet). The engine started ok after I installed the carb and first fired it up and still starts every time now with some pumping. It idles high, even after warming up (missadjusted choke?). I have a stumble in acceleration from idle and I belive the engine would die or at least seriously stall if I hit the gas hard after a stop. The engine also dies sometimes after a cold start when I simply let it idle. In terms of fuel consumption I used about half a tank of gas for about 40 or 50 mls. I may have to check and adjust the float levels again. Is there reason to believe the black fluid from the muffler could be unburned fuel and if so, how can I check this? I believe I could change the intake gaskets myself but I am prepared to take the vehicle to a shop when the head gaskets needs to be changed. However, it does not make sense to tinker around if greater work needs to be executed by the shop anyways. I hope to get some educated opinion and/or assistence in identifing the problem (s) and the decide what to do best.
You need to simplify the troubleshooting process. If you try to assign all the variables to a specific cause, you will be chasing your tail until you are dizzy. (and most frustrated). Test the coolant for combustion gases first and either rule out or confirm that combustion gasses/byproducts are entering the cooling system. This will confirm/elimintate head gasket, cracked head.block or other breach. Second would be proper compression testing, both cold and hot, as well as leak-down testing. The above mentioned tests will require you to purchase testing tools and/or products to complete the testing. (the "combustion/coolant" testing is only about $30 and kits can be purchased online or often locally from auto part stores) Compression/leak-down will cost more to purchase tools and whatnot to perform the tests, and may be easier done by a reputable auto repair shop. The above will go a long way to eliminate or focus "confirmation" on the main issues causing the problem you have. Having folks guess based on what you observe will end up with several paths, and likely frustrate you in the end. (almost always better that a knowledgeable person look at the problem first hand).
Coolant/combustion test would be a testing fluid, changing color if CO2 is in the coolant? Concerning compression test, if results were bad, couldn´t this be caused by bad valves or worn piston rings, too?
Yes, the detector checks for the presence of combustion gasses in the coolant. https://www.truckid.com/lisle/combu...jj8Tl2RLSIAnpnJvfb7cFqg6cLYwPqsgaAuAfEALw_wcB If you spend $25-$30 and either confirm or eliminate the issue of combustion gasses in the coolant. You will be halfway through the issue of cracked head, cylinder or gasket. The compression (and leak-down) tests will give you a pretty good overall indication of the health of the engine, and rule out other problems (that are of greater concern). If the rings are worn to the point of fouling plugs and pour running, or if the valves are not sealing, then worrying about where the coolant is going is not going to gain you much, and replacing gaskets would be moot. **The "black liquid" from the exhaust could be as simple as very rich running, excessive idling or low speed in frequent driving that results in a "wet and sooty" exhaust and not rusty or brown. Or it could be coolant entering the exhaust from several causes, cracked head/valve seat, head, or intake gasket.** Also check the oil to make sure you do not have coolant "disappearing" into the crankcase, then being heated and drawn through the carb and out the tailpipe. The best you will get from "online folks" is "educated guesses" (hence the ** above) and that is not going to truly help you. At this point, if you have a shop you trust to evaluate the car, it might be the best action of time and money and get a definitive diagnosis.
The blackish water is condensation combined with carbon, totally normal on cold start up, the black is from the choke operation.
Test set arrived today. Liquid changed color :-( Will repeat the test later today or tomorrow to confirm, but guess I need to face the possibily that the head gasket may be shot (better than a crack in block or head, fingers crossed). Does it have to be the head gasket or could it be the intake manifold gasket, too? I will talk to my shop and get an estimate to check, confirm and repair. On a side note: While I ran the engine I messed around with my laser thermometer and found the exhaust manifold´s temps way different. The two ports in the middle of each bank were a lot hotter than the outer ones. Is this normal or due to some misadjustment?
Will take vehicle to shop soon to get head gasket replaced (and a lot of other gaskets, too). Hope not to end up with a cracked head or block, fingers crossed!
This is a 340? So no siamesed exhausts like the 350 has. Shouldn't be a big difference in temp but less than 100F I wouldn't worry about. The intake manifold gaskets are likely to leak and will let coolant go directly into the oil. So check that first. Next is the front timing cover. Jim
Sounds like the metal plate is missing under the carb. It protects the carb from the exhaust crossover passage. You will thehave issues you have mentioned with out it.
