Have a 2011 Toyota Sienna with about 50k. Ive been having this problem for over a year but was not very noticeable. But in the last several months, the shudder has increased and the car shakes a good deal when I brake downhill.
The problem does not happen on a flat surface or downhill.
I did some online search and some seem to point to warped brake rotors. Is that likely? Also more importantly, how dangerous is it to drive more in this condition? From where we live we need to negotiate steep downhill every day.
Yes, it is very possible that you have warped brake rotors. This situation is actually not that unusual nowadays, given the thinner material that some brake rotors are made from.
However, it is also possible that you are feeling the ABS kicking in.
Not that ABS should kick-in simply by braking on a downgrade, but it is possible if it is malfunctioning. From your description, it is not possible to tell whether this could be warped rotors or malfunctioning ABS.
I suggest that you have the car examined by a qualified mechanic (preferably NOT a chain operation like Midas, Meineke, Monro, Sear, Pep Boys, or AAMCO) because brakes are certainly something that you should not take for granted. Either way, you should get this properly diagnosed and fixed.
To answer your question, I do not see the abs light on when this occurs FWIW. Otherwise, what would be a sign that abs might be an issue?
The shudder happens most of the time when I go downhill and apply the brakes. I don’t have to press it hard to have this happen. The frequency is about 2-3 times a second maybe when I am going at around 40 mph.
I need to drive for another couple of hundreds miles or so before I can have it looked at. Hope it’s not that dire…
How do you feel the shudder - brake pedal, steering wheel? Probably 1 or 2 warped front brake rotors.
I think I feel it through both (the pedal and the steering wheel). It’s noticeable by other passengers too. The shudder is pretty strong (the whole van shakes pretty strongly). And the firmer I press the pedal, the stronger the shudder it seems.
Not all downhill brakes induce this though. But if the downhill is steep enough, it is pretty reliably reproduced.