Toyota avensis V reg (1999) 2litre. Brake problem on cold start

[ashtony]

Hi I've developed an odd problem....on starting first time in the morning my brake pedal goes 'hard' and the brakes are ineffective after the 2nd or 3rd brake pedal pump. This goes completely after I rev the engine just a bit. From then on the brakes are fine. No warning lights appear.

When I first noticed this I saw that the fluid was low- below the reservoir. It didn' take much topping up. The level has since stayed the same. The problem has not changed and persists.

Grateful for any tips on this thanks. 

[gazza1286]

You probably have a perished hose between the inlet manifold and the brake servo. 

You might be able to hear a faint hissing within the engine bay near the bulkhead on the offside which could indicate a vacuum hose leak. The hose can fail at either end and trimming it may be enough or maybe the clamp is failing. 

Worst case would be a fail servo unit. These should be available from a breaker to keep costs down.  

[Konrad C]

There is a vacuum leak, servo issue, or the non return valve is not holding the vacuum with the engine switched off. What 2 litre engine is your car - 3S-FE, 1AZ-FSE VVTi or the 1CD diesel? 

Haynes manual covers the test procedure for the servo system as quoted in the following - To test the brake servo, press the pedal a few times to exhaust the vacuum (In your case, there seems to be no vacuum!), then start the engine whilst keeping the pedal firmly depressed. As the engine starts, there should be a noticeable 'give' in the brake pedal as the vacuum builds-up. Allow the engine to run for at least two minutes, then switch off. If the pedal is now depressed it should feel normal, but further applications of the brake pedal should result in the pedal getting firmer, with pedal each pedal stroke decreasing with each application. If the servo does not operate as described, first inspect the servo check valve(non return valve).

http://www.japan-parts.eu/toyota/eu/2000/avensis/azt220r-awmehw/3_273540_077_/powertrain-chassis/4703_brake-booster-vacuum-tube#44730

To check the servo check valve, remove the hose to the servo unit, then pull off the check valve. Blow through each end of the valve. You should be able to blow through one direction, but not the other, otherwise it it is faulty. Also check the grommet, hose and connections. If all okay then the servo is faulty!

If diesel (not covered in the Haynes manual), check the vacuum pump. http://www.japan-parts.eu/toyota/eu/2000/avensis/cdt220r-almeyw/3_273540_081_/tool-engine-fuel/1708_vacuum-piping#25770

gazza1286 replied whilst I was typing this, and good advice.