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I am running into a different problem with my BTV. It has been just rebuilt completely but the symptoms remain the same as before the rebuild Instead of failure, i get too much pressure, so that the slightest pressure on the pedal has the car coming to a screeching stop. At the same time there is a groaning sound from the unit. All of the hoses are tight and new. Wheel cylinders and drums and shoes are in very good condition and shoes adjusted properly.

any ideas.


john

IMHO, BTVs are a bit more sensitive than other or more modern systems if that is what you are comparing them to but can't say I remember anyone mentioning the problem you have. If there is no grease or fluid on the linings making them grab, then possibly one of the rubber poppets in the vacuum section has dried or needs attention and the power unit is only working all on or all off instead of proportional to pressure.

Other than cleaning the piston and can, I don't believe rebuilders typically mess with anything in the inner vacuum side because it usually needs relatively little attention and there are no new rebuild kit parts I know of. If it's the same unit you had rebuilt with same problem, Ross has mentioned checking for dried or hardened rubber seals on the vacuum side valves and a method for replacing if any is found. He might have a better idea if the symptom you mention could be caused by a dried rubber part. If you have had more than one rebuilt unit exchanged with the same symptom, then I would look for something external to BTV such as linings.

John Miller Quote:

I would be skeptical of this claim. BTVs were OE on Chebbies, but they mounted up on the firewall. A kit to replace a "BTV" for a Chebbie will not work on a Packard.

Fred Kanter Quote:

No doubt that is true. It is also true that OE units failed for other reasons since they have never been rebuilt by definition. The "15,000lb Elephant in the middle of the room" problem is that the BTV failure (for whatever reason) usually is immediate and total: all of a sudden NO BRAKES. The consequences are ugly.

It is one's own personal choice whether to risk one's life & limb in addition to one's BTV-equipped Packard or not. I chose "not". Everyone makes their own decision.

Craig

On the off-topic of flat tappet cams going flat:

Fred Kanter Quote:

Using the cam manufacturer's break-in lube does NOT solve this problem. As I understand the situation, the problem is the lack of zinc in today's oils. Zinc was removed because it was contaminating the catalytic converters. For a while, one could use Shell Rotella (for diesels which contained zinc) oil for break in. However, once catalytic converters started being fitted to diesels, Rotella was reformulated to remove the zinc, so now that doesn't work.

Now guys are using ZDPplus additive, not only during break in but continually. The flat tappet failure problems have been virtually eliminated for cars with no cat converter.

One of the major reasons for OEMs going to hydraulic roller tappet cams was this situation.

Craig

Just a wee bit of a correction, at least according to published information I've read. The zinc compound ZDDP was NOT removed from Shell's Rotella T, but the concentration of it was reduced. There was data on the amount of reduction in a recent article in Skinned Knuckles. I think I saved the chart, if I can find it I'll add it to this post or summarize the data from it.

EDIT: From the Skinned Knuckles articles. The data was provided by Castrol though they note it is NOT their data.

SAE15W-40 API grade CJ-4 (prior to the reduction): 1374 ppm Zinc, 1150 ppm Phosphorous

SAE15W-40 API grade CI-4 (the current formulation): 1014 ppm Zinc, 819 ppm Phosphorous.

Dave, thanks for the correction/updated information.

However, the gross effect is the same: without enough zinc in the oil, the chance of a new flat tappet failing is much greater. With ZDPplus (there are probably other zinc additive products) the problem seems to be eliminated. I get my information about the failure and solution from Pontiac high performance engine builders who sell thousands of hydraulic flat tappet cams & lifters.

Craig

Howard, thanks for the input. I understand the sensitivity of the units, drove them when new on 53, 55, and 56 Packards and they could be touchy after a brake adjustment. But this is an unusable situation. Rebuilder did a complete rebuild of unit with all Kanter's parts. Unit did what it did prior to rebuild. I also hear vacuum when depressing pedal as well as groan if you hit just the right place. If i depress pedal when turning engine off, it immediately goes to hard and you can hear the air escaping.

It looks like the master will have to come off again and get a going over


again thanks for the input

John

I'm hoping Ross sees this and provides his expertise. He has seen many many more than I. The vacuum should not go away with a single pedal press after turning off the engine. Unless the main check valve is leaking, it should last for 2 or 3 depressions at least. A leaking check valve wouldn't cause your problem--just the reverse with a harder pedal depending on how much vacuum was available at that moment. With the periodic groan, it sounds to me as if one of the poppet valves has hardened and could be leaking or possibly a spring or something else could be broken in the vacuum section.

Howard is correct, the vacuum should not go away with one depression, and the unit should not moan. I believe the reaction diaphragm is breached or its vent plugged. That or the poppets are failing. Send it me and we will see what is what. PM for address if you would like me to look at it.