hidden_hunter Posted March 31 Share Posted March 31 Hi team, Bit of a strange one, I’m having a few issues with my vacuum tank on the 1926 standard. It had been running perfectly for a number of years From what I can tell it’s not making vacuum from the manifold (but my diagnoses could be wrong) what I’ve tried was 1) replacing all the gaskets 2) reseat everything 3) checked all parts moved in the lid 4) pushed gas through from the rear gas tank using air (so lines are clear) 5) blown out all the lines 6) manually filling the vac tank with gas it runs perfectly until it runs dry I can’t think of anything else to check but it all seems to point to lack of vacuum but not sure what would cause that any suggestions? Link to comment Share on other sites More sharing options...
Larry Schramm Posted April 1 Share Posted April 1 Have you taken the fuel pick up tube & filter out of the tank? Could be plugged. Link to comment Share on other sites More sharing options...
Old buicks 2 Posted April 1 Share Posted April 1 How much compression in each cylinder? Link to comment Share on other sites More sharing options...
Roger Barrett Posted April 1 Share Posted April 1 It’s possible, even likely, that the steel tube inside your Marvel heat riser jacket has rusted through. This causes a massive vacuum leak that is undetectable by normal procedures. Remove the intake manifold and look down the riser with a penlight and a pick looking for holes in the tube. If there aren’t any, there will be at some point in the future. The tubes used to be available but now I have to make them. I have done a bunch of these for Buick guys. It’s not a project for the average person. It takes equipment and a machinist. 1 Link to comment Share on other sites More sharing options...
hidden_hunter Posted April 1 Author Share Posted April 1 2 hours ago, Larry Schramm said: Have you taken the fuel pick up tube & filter out of the tank? Could be plugged. Yep cleaned it all out, totally clean 1 hour ago, Old buicks 2 said: How much compression in each cylinder? Haven’t done it for a while but was all within a couple of psi for all cylinders 58 minutes ago, Roger Barrett said: It’s possible, even likely, that the steel tube inside your Marvel heat riser jacket has rusted through Thanks Roger, I think that’s what my next step is Link to comment Share on other sites More sharing options...
Brian_Heil Posted April 1 Share Posted April 1 If it runs perfectly fine by manually filling the vacuum tank then you must have vacuum when it runs perfectly fine and no holes in the heat riser or it would not run perfectly fine then either. I think you have an issue with the SW tank. 2 Link to comment Share on other sites More sharing options...
hidden_hunter Posted April 1 Author Share Posted April 1 1 hour ago, Brian_Heil said: If it runs perfectly fine by manually filling the vacuum tank then you must have vacuum when it runs perfectly fine and no holes in the heat riser or it would not run perfectly fine then either. It just drains the vac tank, it’s not refilling it - is that still the expected behavior? I have a 1.6mm cork gasket on the lid and the banjo fitting has a fibre washer either side. Could either of those be the culprit? Link to comment Share on other sites More sharing options...
Morgan Wright Posted April 1 Share Posted April 1 Take the vacuum tank apart and move the float up and down 100 times and check the valves. It should work every time. I had one that worked 98 or 99 times out of 100 and all it takes is one time not working to mess up your day. I had to tighten (shorten) the springs to get it to work 100% of the time. 2 Link to comment Share on other sites More sharing options...
Morgan Wright Posted April 1 Share Posted April 1 26 minutes ago, hidden_hunter said: It just drains the vac tank, it’s not refilling it - is that still the expected behavior? What Brian was saying is cars don't run without vacuum. Link to comment Share on other sites More sharing options...
Brian_Heil Posted April 1 Share Posted April 1 (edited) SW float could have a leak or be stuck SW internal needle valves at top not seating or little spring broken or linkage broken Flapper valve leaking Crack in lid or bad vacuum sealing at lid or joints Edited April 1 by Brian_Heil (see edit history) 3 Link to comment Share on other sites More sharing options...
DavidMc Posted April 1 Share Posted April 1 Two possibilities, the new top gasket does not have hole for the vent that allows the fuel to flow to the carburetor, or the small brass valve seats cast into the pot metal top are loose and leaking vacuum. Link to comment Share on other sites More sharing options...
Brian_Heil Posted April 1 Share Posted April 1 Plugged vent line is another good one. Yep. 2 Link to comment Share on other sites More sharing options...
Brian_Heil Posted April 1 Share Posted April 1 Plugged vent in the fuel tank cap will also cause issues Link to comment Share on other sites More sharing options...
Grimy Posted April 1 Share Posted April 1 I have TWO lid gaskets on mine, one above and one below the flange of the inner tank, but have seen one-gasket tank models as well. Look for seats that have come unstaked on the suction and atmospheric valves, and has been mentioned, that they operate sharply and in sync--one must be closed when the other is open. Clean any whiskery corrosion from those needles and seats. Integrity (cracks or splits) of vacuum supply line and fittings from intake manifold? Link to comment Share on other sites More sharing options...
nat Posted April 1 Share Posted April 1 Dykes manual has a decent trouble shooting guide. Fill the vacuum tank and run it with the the vent tube plugged. If it floods, the vent valve is leaking. If the flapper leaks, air can get sucked in from the bottom. With a bowl full of fuel in the carburetor, or a gravity feed, run it with the fuel outlet shut off to see if the tank fills. If fuel is available and it still hasn't filled it must be leaky gaskets or tank. Sometimes a vacuum leak can be detected by squirting oil around a seam or gasket to see if gets sucked in. 2 Link to comment Share on other sites More sharing options...
Morgan Wright Posted April 1 Share Posted April 1 I tossed out my cork gaskets and cut rubber ones. I'll use cork when they start making basketball valves out of cork, tires valves from cork, thermos lids and mason jar sealers from cork, and inner tubes. I know they use cork for wine bottles, but they tell you to store the wine bottle on its side so the cork doesn't leak. I bet half the troubles people have with vacuum tanks is the cork gaskets. Rubber seals vacuum 100 times better than cork. Link to comment Share on other sites More sharing options...
hidden_hunter Posted April 1 Author Share Posted April 1 Some great suggestions, I’ll see if I get a chance to try them out this week and report back Link to comment Share on other sites More sharing options...
hidden_hunter Posted April 1 Author Share Posted April 1 10 hours ago, Morgan Wright said: Take the vacuum tank apart and move the float up and down 100 times and check the valves Just tried it by blowing through the fuel hole and moving the float up and down, seems to be sealing ok and moving freely It looks like I’ve got the hole in the right place on the gasket but I might try poking it through with some fencing wire to check it’s clear Link to comment Share on other sites More sharing options...
Hubert_25-25 Posted April 2 Share Posted April 2 The first 3 pages are the notes from when my vacuum tank quit working and left me stranded. Ran great for several months. Last 5 pages are the process I went thru when I rebuilt it. The best gasket to use on the Banjo vacuum bolt are the rubber style inside of the metal ring that Brian Heil found. Hugh 3 Link to comment Share on other sites More sharing options...
hidden_hunter Posted April 2 Author Share Posted April 2 Alright got a bit of time this arvo and took the tank apart verified that the float is in the centre hole and moving freely sprayed wd40 around all the connections to see if it’s sucking anything in (couldn’t see any) cleaned the tank mating surface and made sure it was flat Still no luck Link to comment Share on other sites More sharing options...
hidden_hunter Posted April 15 Author Share Posted April 15 Thought I'd provide an update, we managed to get it going The culprit appears to have been the cork gasket, we switched to a paper one and recut it and is filling correctly once more Thanks for all the advice everyone 3 Link to comment Share on other sites More sharing options...
Morgan Wright Posted April 16 Share Posted April 16 On 4/14/2024 at 9:29 PM, hidden_hunter said: The culprit appears to have been the cork gasket, we switched to a paper one and recut it and is filling correctly once more Why use paper? I use rubber in mine. Link to comment Share on other sites More sharing options...
hidden_hunter Posted April 17 Author Share Posted April 17 21 hours ago, Morgan Wright said: Why use paper? I use rubber in mine. It’s what I had on hand Link to comment Share on other sites More sharing options...
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