| Author |
Message |
Warren E. Smith (Magoo)
| | Posted on Sunday, July 29, 2001 - 12:33 am: | |
Charles, I don't know who told you that the check valve was under the fiberglass cover at the brake booster or what manual they were using, but you can see by these guys where there check valves are located. I would install it there in the vacuum line about 10" away from the intake. Thanks guys for your input, I just wanted to be sure I wasn't incorrect. BRGDS WARREN |
Herbert Edward Gault (Irfgt)
| | Posted on Friday, July 27, 2001 - 5:20 am: | |
My 82 308 valve is about 10 inches from the manifold. |
'75 308 GT4 (Peter)
| | Posted on Friday, July 27, 2001 - 3:17 am: | |
About 10" away from the fitting on the rear, driver's side intake manifold. Basically the same spot as Jeff and you Magoo. |
Jeff Fiedler (Muck)
| | Posted on Friday, July 27, 2001 - 2:37 am: | |
About 8 inches up the hose leaving the left rear carb intake, its small only about 3/4 long. 78 308 GTS |
Warren E. Smith (Magoo)
| | Posted on Friday, July 27, 2001 - 1:03 am: | |
C'mon Guys, Where is your check valve for your brake booster on your 79 308 GTS or GTB. Curious. |
Warren E. Smith (Magoo)
| | Posted on Wednesday, July 25, 2001 - 11:45 pm: | |
Charles, my car is a 79 308 and the valve is located in line in the engine bay. Regardless the valve still serves the same pupose as long as it is in the line. My car is a pretty orig. car with the orig vacuum hoses. I would like to hear comment where the check valve is located on other 79 308 GTS or GTB cars. Charles your power booster should function better with the check valve installed. Thanks. |
charles claussen (Atlantaman)
| | Posted on Wednesday, July 25, 2001 - 10:38 pm: | |
out of curiosity, I did some investigating and discovered that the check valve is actually supposed to be located in the front, near the brake booster and not in the engine bay of the car. The service books and several mechanics have confirmed this---never the less--my car still did not have one. There is one with the vacuum tank that I bought so that was likely the reason for the improved brake performance. |
charles claussen (Atlantaman)
| | Posted on Friday, July 13, 2001 - 8:27 pm: | |
i looked for the check valve and for some reason(great italian manufacturing) there was not one anywhere...
Also just to satisfy my curiosity,I removed the hose to the booster, plugged one end and hooked it to my air compressor. Then placed in a bucket of water--guess what--- full of leaks. Will replace it and install a check valve. |
Warren E. Smith (Magoo)
| | Posted on Tuesday, July 10, 2001 - 12:08 am: | |
OK Don , the valve is in the area of the oil filter. You can't miss it. Remember the arrow points to the carb. engine, on the valve when re-installing it. |
Don Norton (Litig8r)
| | Posted on Monday, July 09, 2001 - 11:45 pm: | |
Thanks for the excellent idea Warren. I'm going to do that tomorrow. |
Warren E. Smith (Magoo)
| | Posted on Monday, July 09, 2001 - 11:43 pm: | |
Also Don, about the statement of no power assist when you are at idle and coasting is just not true. If that engine is running and idleing the proper rpms and the vacuum system is working properly you should have power assist. |
Warren E. Smith (Magoo)
| | Posted on Monday, July 09, 2001 - 11:28 pm: | |
Don, the valve is looking at you when you raise the bonnet. It is on the left side of the engine. It is silver,looks like a PCV valve. It is in line on the large vacuum hose. When you clean the valve use brake clean aerosol let it sit and then use a blunt instrument, such as not to damage the valve, and push the valve plunger back until you feel the spring tension pushing the plunger closed. You should then be able to blow air thru one side and not be able to blow air thru the other side. |
Don Norton (Litig8r)
| | Posted on Monday, July 09, 2001 - 11:02 pm: | |
You know I did mean to do that but haven't yet. I tried to locate the applicable hose in a service manual, but didn't find it. And the book was in Italian. Could you give me a little more info on how to find the right one? |
Warren E. Smith (Magoo)
| | Posted on Monday, July 09, 2001 - 10:51 pm: | |
Also Don if this check valve was stuck partially shut you would'nt get full vacuum to the booster when it called for it. |
Warren E. Smith (Magoo)
| | Posted on Monday, July 09, 2001 - 10:48 pm: | |
Don, did you remove the check valve and clean it? Also as I previously mentioned about the dash pot which slowly closes the throttle, is it working properly? And finally is the idle set at 1000 rpms without the A/C on? These things, even though they seem simple could cause your problem. P.S. When you clean and re-install the valve , be sure the arrow on the valve points toward the carb. or engine. |
Don Norton (Litig8r)
| | Posted on Monday, July 09, 2001 - 8:27 pm: | |
Well, I appreciate everybody's input but I still don't know what to make of it. I'm going to keep a sharp eye on it for sure. I heard from the car's former owner today, who seems to be an honest sort. I noticed the fade on the test drive while we coasted up to a stop sign out of gear and we talked about it briefly.
He told me today that it has done that in the 2 years that he owned it, and he asked the local Ferrari Shaman about it back in the day, and the opinion was that brake power is tied to engine RPM. When you take it out of gear and coast, no RPMs means no power assist.
As nutty as this sounds to me, it does jive with what is in the owners' manual and other things that I've found on the net. And the only time it's happened to me is in that exact same scenario, like when I'm coasting up to my garage door when I return home and braking very lightly.
I don't know where I picked up the habit but I don't engine brake. I've now started leaving the clutch engaged until right before I come to a stop, and the brakes are just peachy.
So, right now, I'm learning and observing, and I appreciate everyone's input.
-DN |
BretM (Bretm)
| | Posted on Monday, July 09, 2001 - 6:08 pm: | |
My brake failure light is on most of the time. I know there is enough fluid and it's not leaking, I think there is a pressure imbalance between the right and left front brakes. Ahh, brakes, who needs 'em anyway. |
Warren E. Smith (Magoo)
| | Posted on Sunday, July 08, 2001 - 10:53 pm: | |
Don, What do you think, or better yet what have you found? Do any of these suggestions from the guys give any help? Curious. |
Steve (Steve)
| | Posted on Sunday, July 08, 2001 - 8:42 pm: | |
I agree with Warren. My 77GTB does not have this problem and if you think about it your vaccum is highest at idle or coasting in gear. Should be around 20-25 inches. This being the case you would have the most vaccum at the brake servo. It sounds like a vaccum leak somewhere or leaking brake fluid . Do a vaccum check and see what you get. Try the tests described in the ONLINE FERRARI MAINT. Manual on this site. Steve |
Jeff K (Jbk)
| | Posted on Sunday, July 08, 2001 - 3:34 pm: | |
Peter, I heel and toe like you do: rolling the ball of my foot half on the brake, and other half on the throttle. I found the throttle pedal a little to far back in relation to the brake to effectively do this when I'm at high rpm's, however, so I added a plate spaced about 3/8" off the gas pedal. Works great now and I can rev the engine as much as I need to match rpm's.
By the way, my friends 328 has the gas pedal more even with the brake pedal, rather than set back like on my 77 308. |
'75 308 GT4 (Peter)
| | Posted on Sunday, July 08, 2001 - 1:29 am: | |
Good point about the check valve Magoo, these little items get over-looked.
About compression braking: It involves good technique, ie: proper heel-and-toeing. Speaking of that, its probably just me, but both my 308 and my daily driver, I can't do the correct heel-and-toe (ball of foot on the brake and blip throttle with heel). What works for me is to have half the ball of my foot on the brake and rock over the other half to blip the throttle. Works every time. How do you (Rob, William, other racers and everybody else) do heel-and-toe? |
Warren E. Smith (Magoo)
| | Posted on Saturday, July 07, 2001 - 11:55 pm: | |
Another thought that comes to mind is the check valve located in the vacuum line at the engine. You might want to remove it and clean it out with some brake clean. It may be working sluggish. |
Warren E. Smith (Magoo)
| | Posted on Saturday, July 07, 2001 - 10:45 pm: | |
Not to critcize ones driving habits here but why would't you let the engine compression slow you down rather then riding the clutch to a stop? Is your dash pot working properly. This may cut the engine rpms way back too soon and almost stop the engine causing a loss of vacuum. Is your engine idle set at 1000 rpms at idle. I have a carb. 308 GTS and never had a problem. I don't think it's a design issue. Something else seems to be wrong. |
Don Norton (Litig8r)
| | Posted on Saturday, July 07, 2001 - 5:28 pm: | |
Charles -
That sounds like the same problem I have. I usually depress the cluth and very lightly brake when I know it's a long way off. Apparently not a good idea in a 308. Before I bought the car I had the mechanic do a vaccum test (about 3 weeks ago), so it sounds like a design issue rather than an acute problem. I presume a mechanic of reasonable skill (not me!) could put this in?
Thanks for the suggestion.
-DN |
charles claussen (Atlantaman)
| | Posted on Saturday, July 07, 2001 - 4:12 pm: | |
PS..getting the booster out of the car is NOT easy |
charles claussen (Atlantaman)
| | Posted on Saturday, July 07, 2001 - 4:11 pm: | |
I purchased a basic aluminum reservoir and installed it under the spare tire next to the horn--had to run additional hose to and from it but it seems to work well--
by the way--the way I decided to attack the vacuum was just a gut feeling. On leaving the interstate I usually brake slightly at the start of the ramp them coast up to the light before braking hard. the second time on the brakes was at great effort unless I revved up the moter between braking. logically i used up all my vacuum and needed a volume booster |
Don Norton (Litig8r)
| | Posted on Saturday, July 07, 2001 - 3:15 pm: | |
Charles - which Summit part did you buy and what's the installation like? Thanks.
-DN |
Adelina Vallese (Dina)
| | Posted on Saturday, July 07, 2001 - 2:16 pm: | |
Low, as 'Magoo' has said the boosters are rebuildable. Chuck, if there was a loss of vacuum,
did you find the cause before fitting tank? |
charles claussen (Atlantaman)
| | Posted on Saturday, July 07, 2001 - 10:28 am: | |
my 80 308 has always done this and it was indeed a problem with loss of vacuum. I ordered a vacuum "reservoir" tank from summit racing, installed it--no more problem.
chuck |
Warren E. Smith (Magoo)
| | Posted on Friday, July 06, 2001 - 4:41 pm: | |
Low, Whitepost restorations advertises they can overhaul that booster. So to answer your question, I guess they can be overhauled. |
Low Kai Chin (Speeddemon)
| | Posted on Friday, July 06, 2001 - 6:15 am: | |
Hi Adelina - U mentioned changing the diaphram. Is this possible or even advisable? Or are U refering to changing the entire brake booster? |
Adelina Vallese (Dina)
| | Posted on Thursday, July 05, 2001 - 9:14 pm: | |
Don't waste time! We're talking Ferrari and your life here.First flush and bleed out the whole system. Check all brake lines for leaks & flexible lines for expansion.When the flexible lines get old they can expand thus giving you a low or sinking pedal.This will happen especially if the discs are worn and overheating. The calipers rarely cause problems but if you are doing the Master, then it might be worth having the calipers done too. If all the lines and calipers are OK, then I would immediately pull the master cylinder and have it re-sleeved with stainless steel inserts(cheaper and better than buying a new one) and put a new seal kit in it.Any reputable brake place could do this. Also check the Master Vac unit for vacuum leaks. It may need a new diaphram as well. Do it now ! Brakes are something you do not put off. |
Warren E. Smith (Magoo)
| | Posted on Thursday, July 05, 2001 - 8:12 pm: | |
What Peter says is probably true however if you are sitting, stopped,with the engine running, with pressure on the pedal and it slowly goes to the floor, the master cylinder could be leaking down. Just check that to be sure. |
'75 308 GT4 (Peter)
| | Posted on Thursday, July 05, 2001 - 12:43 pm: | |
What is said in the manual refers to having the engine off and coasting to a stop. Since the engine wouldn't be running, you're not getting the vacuum assist to the power booster and therefore makes it harder to press the brake.
In your case though, you've got air in your system and it needs to be bled (happened once to me in my daily driver, scared the living s--- out of me). |
Rob Lay (Rob328gts)
| | Posted on Thursday, July 05, 2001 - 8:50 am: | |
I would be curious to hear if that's true, that's kind of my style also, but I haven't had any problems with the 328.
It may to air in the brake lines. |
Don Norton (Litig8r)
| | Posted on Thursday, July 05, 2001 - 8:31 am: | |
Hey everybody -
I was out yesterday in my '78 308 and noticed that every once in a great while my brake pedal would lose resistance and go almost to the floor before stopping. I remember reading in the owner's manual that you're not supposed to coast up to a stop before braking, or else the system would lose the power assist (I don't know what dumbass designed that!). Unfortunately, my driving habit is to do exactly that, and the problem only seemed to appear at that time.
Anybody else have this problem? I have difficulty thinking this is normal. I've now started leaving the car in gear and not putting the clutch in until I'm almost stopped, and the problem hasn't reappeared. Kind of scary though!
-DN |