I have completely flushed Popeye's block and radiator with vinegar. Lots of crud came out, was worth the effort. As measured by my infrared thermometer, the temperature drop from the top of the radiator is now about 75 degrees (185 at top, 110 degrees at bottom. So I believe the radiator is doing its job. I installed the new drain petcock and it seals nicely.
The car starts and idles well when cold. After the first few minutes I can advance the spark to about the 8-or-9-oclock position and achieve a smooth idle.
However, when the engine heats up to operating temp (185 degrees by my thermometer), it begins to run rough and I can see bubbles appearing in the radiator water (no bubbles when first starting). The car won't idle smoothly at that point, will die if I try to lower RPMs to 'normal' idle range. No change in rough running condition if I adjust the carburetor.
Compression measures a consistent 40 pounds per cylinder for all four cylinders - so I don't believe valves or cracked block are a problem. There is no water in the oil. No oil slick on the radiator water.
I theorized in another post that the head gasket could be the problem because I was seeing the bubbles in the radiator, but hesitated to touch that until all other possible problems are eliminated.
So before I lift the head, does it sound like head gasket to you experts? I have a new copper head gasket on hand and it doesn't seem like a difficult job except possibly the rear bolt - would like to avoid having to raise the body in order for bolt to clear, but will do it if necessary.
I'm beginning to be very discouraged with this car. Every time I think I will have it running well enough to drive with confidence, something else happens. I don't have any basis for comparison as I've never driven another Model T, and have not had the benefit of the expertise of another T owner. So I'm navigating in the dark.
I really do like this car, but much more of this and I may just dump it and go back to another Model A.
So please, what's your considered opinion? Head gasket? Or is there anything else you can think of?
(Message edited by cliff colee on May 17, 2017)
RE; The car starts and idles well when cold. After the first few minutes I can advance the spark to about the 8-or-9-oclock position and achieve a smooth idle.
You should be advancing the lever as soon as the engine starts.
RE; would like to avoid having to raise the body in order for bolt to clear, but will do it if necessary.
You just leave the bolt in the hole, not sure where you got the info that you would need to lift the body!
Besides it's the back two bolts and when you go to install the head, put those two bolts in the holes and hold up with something like cloth pins or a wire wrapped around them.
Cliff, I have experienced a similar problem. All is well until engine gets warm. I ended up removing the head and having it planed. It was warped to the point that I was getting blow-back into the cooling system. Good luck........
I think once started you pull the spark lever down to at least 25 to the hour.Are you adjusting the carb to lean? Bud.
Mark is correct in instructions to advance lever as soon as car is running.
John has probably diagnosed your problem. A simple fix. Search for some threads regarding chasing threads in block and cautions against overtightening...
I use copper cote on head gaskets with great success
This isn't really a big deal
Mark: thanks for that bit of info. Good to know I don't have to deal with lifting the firewall.
Bud: When the car is warmed up I can turn the carb down until the engine begins to stumble, then turn it the other way until it stumbles, then turn to the halfway point between the two 'stumble points'. Does not make a difference.
I do pull the spark advance down upon startup, to about the 9-10 o'clock position. Seems to run smoothest at 8-9 o'clock when warmed up.
John: If I have to pull the head I will certainly have it planed level. Good to know this is not a unique problem....
Do all the adjustments to the spark lever and carburetor leaner than it is. Try driving the car around a bit and see how it runs. It will run hotter if you let it idle than when you drive it because the air will blow through the radiator when you are driving it. You might not be seeing air bubbles but it might be boiling. The heat distribution is not completely the same all the way through the engine, so it might be boiling in one area but not be boiling at the area where you are taking the temperature.
If all other things fail you, then you can pull the head. But that would be the last thing I would do unless you find something like water coming out the exhaust when it is warmed up, or water in the oil. You wouldn't necessarily notice water in the oil until you change the oil. However it will usually foam up if very much water gets into it.
Are you getting enough air flow thru your radiator?
Cliff,What year are you talking about? Bud.
Cliff, What ever you do, don't get discouraged. I'm sure with all the T brain-power here, the problem will surely be diagnosed. I have a questions for you since it seems your not sure if its overheating or not, but just seeing bubbles. Does your radiator actually blow steam or fluid out of the overflow tube when you think its overheating?
How about a leakdown test on each cylinder to see if you are getting compression into the cooling system and where is it coming from if it is.
When and if you pull the head check the gasket for the proper amount of holes at the water jacket passages. It is not impossible to get a badly punched head gasket. Also a large piece of scale inside the engine can block circulation. Make sure the fan is turning properly, a severely stretched belt can move the fan but slip quietly causing a loss of air flow.
Puzzler. Was the comp test done hot or cold? The reason I ask is you're getting radiator bubbles/rough running when it heats up so there's a change happening at that point that might not show when a cold comp test is done. You seem to have done your diagnostics and if spark & fuel are OK I believe a head job is in your future.
If you think it's a timing problem start at the beginning and check your timing setting to be sure it's correct to start with and that you set it on the compression stroke. After you're sure the timing is correct check to see that the rod is in the proper position it may need tweeked. If the timing is correct the lever should be at the top of the quadrant.
What do you consider boiling? The Model T will gurgle and make noise when you shut off the engine. If you fill the radiator too full it will over flow until it finds the proper level which should be just above the fins, the tank should not be full of water, that area is used for water expansion.
When I run my cars my timing handle is pulled down to the seven o'clock position.
I'll attempt to post the manual throttle/ timing chart.
Sounds like a head gasket to me and that really isn't difficult to change. I use spray on copper coat and MAKE SURE you put the head gasket on the right way. If you do it wrong you will block some of the large passages.
If you're at 185, with a 75 degree temp drop, you're not over heating. It does sound like a bad head gasket. Your compression test sounds good, however, was it done immediately after the car began to run poorly, or was it when the car was cold? As others mentioned, I would have the head planed and put in a new gasket. I prefer the copper ones, especially if you have an aluminum head.
Keep the faith buddy, it gets better.