[BuickCrazy]

We purchased a 1949 Roadmaster Sedanette about a month ago. We have had it out for drives a number of times with no problems. However, about two weeks ago we drove to a friends house about 10 miles away and on the way home, about a mile from our house at about 45 mph it started to make a popping noise, similar to popcorn popping. I slowed down and it went away. I thought it might have been a stuck thermostat causing the engine to over heat so I changed the thermostat. took it out and same thing. The car starts with no problem, idles without hesitation, runs well at speeds under 30 mph, but get up over 30 and the noise starts. The popping is erratic and doesn't seem to be in sync with rpms or anything like that. The only thing I have done to the car is fill it up with premuim and added some lead substitute. Any ideas what might be happening?

Randy

[Pete Phillips]

Wheel bearing? Universal joint? Rocker arm? Where is the noise coming from? Under the passenger compartment? Under the hood? Is the pavement rough when it does this? Does it do it when car sits still but engine speed is raised to what it would be at 45 mph? I would do that, and take the valve cover off to see if anything is loose under there.
Pete Phillips
1949 Super Estate Wagon
1948 Roadmaster 4-dr.
1950 Roadmaster 2-dr. ht.
1959 Electra 2-dr. ht.
1962 Electra 225 4-dr. ht.
1963 Wildcat conv. 4-spd.

[BuickCrazy]

Pete

Thanks for your reply. I don't know exactly where the noise is coming from since it only happens when I am going over 30 or 40 mph. I think it sounds like it is coming from the engine compartment. Each time it has occurred it has been on a smooth asphalt surface. The last time it did it, I got it home, put it in park, raised to rpm's to what I think they were when it started making the noise and held it there for a couple of minutes. No noise. The lifters do sound a little clicky to me when I am under the hood. I beleive this car has hydraulics and should not be noisy. This weekend I am going to put some GM EOS to see if that will make the lifter noise go away and maybe also the popping noise I hear at cruising speed.

Randy

[JohnD1956]

If this "popping" happened while you were putting a load on the car ( maybe driving up a small hill in 3rd gear), it may be backfiring into the aircleaner. I am going through this right now with my 78 and it seems to be a lean condition caused by any of several issues:

1- choke not fully opening
2- dirt/sediment in the bowl of the carb
3- incomplete manifold warming due to faulty heat riser
and/or 4 - maybe vacuum leaks

I noticed the backfiring seems related to how deep I press the accelerator, and if I keep the accelerator at that position but shift to second gear, the backfiring stops immediately.

If your symptoms are similar this may be what's happening.

[kaycee]

Sometimes an engine will miss under load and still idle and run at low speeds fine. I've found on my older Buicks and other cars that all they needed were points and plugs or plug wires if they 'popped' or missed at higher speeds, assuming that the air filter, gas filter, and the usual tune up parts were o.k.
You might want to put a quart of Rislone in the oil too, in the event you have some sticking valves or lifters .
kaycee

[RM41]

I had a simular problem with my 48', an older gentleman (84) who is very knowledgeable with older cars said it was my plug wires, I replaced them with very good ones and Problem Solved.
Kevin

[JohnD1956]

I agree, and suggest this is the first place to look, if Randy determines his popping is actually backfiring. I already replaced all that stuff, and more on my 78.