A hissing noise .......

[TR Tony]

....... comes from the front of my TR8 when I press the brake pedal. Its the kind of noise you get when you open a bottle of fizzy water!

The pedal also seems to "give" a bit, although the brakes are working well enough, & the pedal is firm after that initial "give"

I believe there is a seal between the servo & the bulkhead? Could this be leaking air when I apply the brakes? Any thoughts gratefully received!

Tony

<font size="1">1981 2L FHC Cavalry Blue
1980 3.5L V8 DHC Jaguar Regency Red - sadly sold!
TR8 FHC EFI Factory development car Inca Yellow</font id="size1">

[Beans]

Seal between servo and bulkhead is only there to keep moisture and nasty vapours out of the interior.
If the servo is blowing there are a few possibilities;
1. Seal between servo and brake cylinder gone;
2. Seal vacuum connection perished;
3. Servo itself not sealing properly or damaged diaphragm.

<center>
<font color="blue"><i>1981 TR7 FHC Sprint (better known as 't Kreng)
1980 TR7 DHC (my first car currently being restored)
In parts a 1980 TR7 PI DHC, 1981 TR7 DHC, 1981 TR7 FHC</font id="blue">
<font color="red">http://tr7beans.blogspot.com/</i></font id="red"></center>

[V8Wedgehead]

I also found that if you pump the brake pedal quickly it will raise the idle up and that is the sign of a bad brake booster. You need to get a rebuild kit (not fun to do), get one rebuilt or if it is a TR7 find another booster. The TR7 & 8 booster are different but can be interchanged. The TR7 one has more of a firm feel than the TR8.

Michael
1980 TR8 FHCs; Rally Conversion #0020 & Stock #0058

If it is broken then fix it....if it is not then make it faster!"

[bmcecosse]

There will always be a 'hiss' as the servo acts - but just momentary - not continuous.

[busheytrader]

Hi Tony,

My first thought would be the vacuum hose connections from inlet manifold to servo if it's heard more from the front as opposed to the interior.

My original factory fitted hose clips were just bent wire. As the hose shrunk with age the hose slopped about and I guess lost some of its seal at either end.

Might help.

Adam



TR7 V8 DHC Jaguar Solent Blue. 9.35cr Range Rover V8, Holley 390cfm, JWR Dual Port, 214 Cam, Lumention, Tubular Manifolds, S/S Single Pipe Exh, 3.08 Rear, 200lb Spax & PolyBushes all round, Anti- Dive, Top Roller Bearings, Capri Vented Discs & Calipers, Braided Hoses, 4 Speed Rear Cylinders, Uprated Master Cylinder & Servo, AT 5 Spokes and Cruise Lights. S/S Heater Pipes. No Door Stickers. Mine since July 1986, V8 from 1991

[TR Tony]

Thanks guys - I will check for lose or perished connections first! Hopefully a rebuild is not required[:(]

Tony

<font size="1">1981 2L FHC Cavalry Blue
1980 3.5L V8 DHC Jaguar Regency Red - sadly sold!
TR8 FHC EFI Factory development car Inca Yellow</font id="size1">