Engine: Oil Cap pops off

[jhwestcott]

It's happened twice now, I thought the first time I just didn't put the cap down tight. It's on an early 62 289 with the bypass oil filter.

[warrlaw1]

They are supposed to breathe. Mine sits on there pretty loosely. Only time I've seen one blow off (and the dipstick blow out too) is when an engine fired in the crankcase. We were trying to start a 283 and poured gas down the carb, not knowing there was a hole in a piston. Kaboom. Dipstick parted my buddy's hair and the oil cap bounce off his forehead.

[Dick Steinkamp]

Crankcase pressure will do that if either the filter in the oil cap and the road tube and/or pcv valve are blocked or at least partially blocked.

If you have a road tube, it will be coming out of the valley cover (below the intake manifold, then down along side the engine to about the middle of the oil pan. There should be a cotter pin in the bottom of it holding some steel wool acting as a filter. Remove the cotter pin and steel wool and make sure the tube is clear by running a stiff wire up it. Replace with new steel wool and pin.

If a PCV valve, the valley cover will have a fitting where the earlier cars had a road tube. A hose on the fitting should lead to a PCV valve either in line to the base of the carb or directly fitted to the base of the carb. Insure the PCV valve is working and installed in the correct direction.

Regular maintenance (each oil change) should include washing out the oil fill cap in solvent and reinstalling it.

[BobWaitz]

We lost one off David Livesey's Avanti on its first run at Bonneville this year. We had to wire it on like we did with the Salt-2-Salt car.

[jg61hawk]

What kind of car with what engine? I just looked in the Shop Manual for my 1961 Hawk and reviewed the six vs the eight. I believe only the six cylinder models have the filter in the road tube. The eights apparently only use the oil filler cap as a filter.

I agree with Dick above it sure sounds as simple as a crankcase ventilation problem. Look in the Shop Manual for your engine and look under oiling. It will describe how to maintain what you have.

[skyway]

Per Warren's story, just for the heck of it, smell/check the dipstick to be sure a bad fuel pump is not sending explosive gasoline into the crankcase.

[lark55]

Would worn rings cause the crankcase to be over-pressurized and blow off the filler cap?

[StudeRich]

Would worn rings cause the crankcase to be over-pressurized and blow off the filler cap?

Yes, also stuck Rings and blow-by from worn Valve Guides and Valve Seals.

[JoeHall]

Short of an explosion in the crankcase, i.e. backfire with a hole in a piston as mentioned above, I cannot imagine the motor building that kind of pressure, under anything like normal circumstances. The caps normally breath in, but could breath out if the crankcase were to become pressurized. I'd think, if that kinda pressure is building in the crankcase, the motor would also be leaking like a sieve from places like oil pan gasket, valley cover, rocker covers, front & rear crank seals, etc.

You'd also be getting watery eyes from seriously excess blowby.

I'd guess its more likely that the cap fits too loose. All of mine require a pretty good tug to remove them.

[SN-60]

Crankcase pressure will do that if either the filter in the oil cap and the road tube and/or pcv valve are blocked or at least partially blocked.

If you have a road tube, it will be coming out of the valley cover (below the intake manifold, then down along side the engine to about the middle of the oil pan. There should be a cotter pin in the bottom of it holding some steel wool acting as a filter. Remove the cotter pin and steel wool and make sure the tube is clear by running a stiff wire up it. Replace with new steel wool and pin.

If a PCV valve, the valley cover will have a fitting where the earlier cars had a road tube. A hose on the fitting should lead to a PCV valve either in line to the base of the carb or directly fitted to the base of the carb. Insure the PCV valve is working and installed in the correct direction.

Regular maintenance (each oil change) should include washing out the oil fill cap in solvent and reinstalling it.

Or better yet, throw the steel wool or 'Rats Nest' away!

[jnormanh]

Barring some serious blowby into the crankcase it sounds Iike the cap is past due for it's 50 year cleaning.

[jg61hawk]

This has nothing to do with the "problem" but most of you live far away from me, so I doubt I'll ever meet you guys. I just wanted to say if you look at the responders to this post and add up the number of posts you guys are great! You guys come across as a very reasoned T-H-I-N-K-I-N-G types of guys that like so many on this forum make this club great. I've done some nice give aways but rarely have contributed any real substantial knowledge like Bob Palma, and so many others. This post shows the essence of what makes this club great. Some humor, (past due for it's 50 year cleaning) CREDIT:jnormanh, some good advice, some comments, and just general good old fashioned guys talking cars. I had no idea oil caps ever blew off....but if that is a problem for you....we're gonna stop that! Look at these guys stepping up to the plate for the new guy with one post......Great Club...Long Live Studebaker!

[Warren Webb]

My 61 Champ lost it's oil filler cap while on the freeway. I figured it was due to the engine being tired & needing an overhaul. When I got my 62 Champ the previous owner had rigged up a retainer that slipped over it's filler cap to hold it on. Compression is low in a couple of cylinders on this one and the heads are mismatched. I have an extra pair of the correct heads that I'm going to have done so it should be a one day swap. That is unless I go ahead & install the 2x2 manifold I just got or go with a Edelbrock AFB to replace the 2 bbl that's on there now.

[altair]

breather cap

It's happened twice now, I thought the first time I just didn't put the cap down tight. It's on an early 62 289 with the bypass oil filter.

I would like to suggest a comprehensive vacuum test, there are about 9-10 various tests to determine engine condition. This will give you a better understanding of your engine condition. It will determine where the most probable leaks are occuring. There was an earlier post about cross fireing it would be good to review that post. I would further suggest to run your engine at night and inspect it in the dark for unwanted ignition cross fireing, this may tell you something.

[jclary]

I'd guess its more likely that the cap fits too loose. All of mine require a pretty good tug to remove them.

I'm suspecting that, barring some additional specific input from the original poster, Joe has given the most likely answer. If this Hawk is the early version, it still has only one oil filler cap located on the filler standpipe in the center of the engine and not on the valve cover. That, on my GT was directly in the path of high velocity discharge air from the fan shroud. If the clips on the oil cap are not holding tight, that cap could work its way up and be blown off the filler tube.

This post is a good example of a "drive-by" posting...where the problem is stated and the poster leaves the room for a while. Hope he returns soon and fills us in.