Technical 1993 Type 290 Brake Servo

[Stevetyphoon]

Hi,
My 1993 Hymer 2.5 TD Type 290 seems to run out of vacuum too easily. Recently passed MOT no problem but on a long downhill with a full stop at the bottom, I've had to resort to the handbrake. Only happened a couple of times but unnerving.
Anybody experienced the same and will replacing the brake servo solve it?
I've been trying to source a new servo with no luck. Any pointers?
Any advice much appreciated.

 

[bugsymike]

Hi,
My 1993 Hymer 2.5 TD Type 290 seems to run out of vacuum too easily. Recently passed MOT no problem but on a long downhill with a full stop at the bottom, I've had to resort to the handbrake. Only happened a couple of times but unnerving.
Anybody experienced the same and will replacing the brake servo solve it?
I've been trying to source a new servo with no luck. Any pointers?
Any advice much appreciated.

Switch engine off, pump brake pedal to empty servo, press foot on brake pedal and start the engine, you should notice the pedal drop away as servo assists noticeably.
Next start engine with foot off brake pedal, switch engine off wait a few minutes and press brake pedal repeatedly, you should get several presses with servo assistance before pedal goes hard.
Next after emptying servo by pressing pedal repeatedly, pull off if possible the vacuum pipe to servo, put finger over end and have someone start the engine, a good vacuum sucking on pipe should be felt. If not check for air leaks on pipe.
If no leaks then check the brake vacuum pump on unit below injector pump by oil filter housing etc.
Note if poor oil supply to brake vacuum pump it can reduce pumps effectiveness.
Finally if none of the above are you sure the brake hydraulic side is good, this is if when trying to stop and the brake pedal is spongy rather than hard but not stopping due to lack of vacuum.

 

[Stevetyphoon]

Hi Mike, big thanks for the quick reply.
I've previously done the checks with engine on/off pumping brake pedal etc and all seems to work.
To re-check, I've just followed your instructions and the vacuum seemingly works as it should on engine starting.
Been a bit nervous about getting the vacuum hose off - it is very tight.
Any top tips getting that off?!
No spongy brakes, the pedal goes solid.
(On a Hymer forum, opinion seemed to be split between getting hold of a new or refurbished servo as the design some say isn't great. One person paid £700 for a servo and the problem didn't go away.)
When I get the hose off (which actually looks quite new) I'll put my finger over it but how do you know if it is enough 'suck' or not?
Cheers
Steve

 

[bugsymike]

Hi Mike, big thanks for the quick reply.
I've previously done the checks with engine on/off pumping brake pedal etc and all seems to work.
To re-check, I've just followed your instructions and the vacuum seemingly works as it should on engine starting.
Been a bit nervous about getting the vacuum hose off - it is very tight.
Any top tips getting that off?!
No spongy brakes, the pedal goes solid.
(On a Hymer forum, opinion seemed to be split between getting hold of a new or refurbished servo as the design some say isn't great. One person paid £700 for a servo and the problem didn't go away.)
When I get the hose off (which actually looks quite new) I'll put my finger over it but how do you know if it is enough 'suck' or not?
Cheers
Steve

A bit of WD40 may help, is it the hose connection or a plastic fitting in a rubber grommet in the actual servo drum?
Also did you empty the servo first by pressing the pedal as the vacuum holds it on.
Vacuum is usually fairly strong so once finger sealing it you may be able to lift the pipe by moving your finger, a bit like testing a good vacuum cleaner with your hand on the pipe, but not quite that strong.
I assume you can not see or hear any leaks on pipe down to vacuum pump?

 

[bugsymike]

If when testing the servo after five minutes after engine off and you can get several good presses before the pedal goes hard then I would say not much wrong with servo it's self.
More likely a pipe or the vacuum pump.
Just one small point, I am assuming the servo has the brake master cylinder bolted to it and not an independent servo unit mounted elsewhere on the vehicle with it's own hydraulics?

 

[Stevetyphoon]

A bit of WD40 may help, is it the hose connection or a plastic fitting in a rubber grommet in the actual servo drum?
Also did you empty the servo first by pressing the pedal as the vacuum holds it on.
Vacuum is usually fairly strong so once finger sealing it you may be able to lift the pipe by moving your finger, a bit like testing a good vacuum cleaner with your hand on the pipe, but not quite that strong.
I assume you can not see or hear any leaks on pipe down to vacuum pump?

It's a grommet type thing. I didn't pump the pedal before trying to remove the hose.
I'll try tomorrow.
No hisses from the hose.

 

[Stevetyphoon]

If when testing the servo after five minutes after engine off and you can get several good presses before the pedal goes hard then I would say not much wrong with servo it's self.
More likely a pipe or the vacuum pump.
Just one small point, I am assuming the servo has the brake master cylinder bolted to it and not an independent servo unit mounted elsewhere on the vehicle with it's own hydraulics?

Probably only 4-5 good pumps on the pedal.
Master cylinder bolted to servo.

 

[bugsymike]

It's a grommet type thing. I didn't pump the pedal before trying to remove the hose.
I'll try tomorrow.
No hisses from the hose.

4-5 pumps is OK, check on one of your other vehicles to compare.
So I am guessing that the hose is fitted to a plastic one way valve pushed into the grommet, in that case empty the servo, spray a little WD40 around the plastic grommet then using a wide flat blade screwdriver to gently prise the plastic valve out of the grommet whilst gently twisting , I find works.

 

[Stevetyphoon]

So I am guessing that the hose is fitted to a plastic one way valve pushed into the grommet, in that case empty the servo, spray a little WD40 around the plastic grommet then using a wide flat blade screwdriver to gently prise the plastic valve out of the grommet whilst gently twisting , I find works.

Cheers Mike, I'll give that a go tomorrow.

 

[Communicator]

4-5 pumps is OK, check on one of your other vehicles to compare.
So I am guessing that the hose is fitted to a plastic one way valve pushed into the grommet, in that case empty the servo, spray a little WD40 around the plastic grommet then using a wide flat blade screwdriver to gently prise the plastic valve out of the grommet whilst gently twisting ,

Cheers Mike, I'll give that a go tomorrow.

May I suggest silicone based lubricant spray instead of WD40, which can damage some plastics. I had an expensive experience some years ago with a stretched nylon tyre on a sliding door roller. I could only blame the stretching on contact with WD40.

 

[bugsymike]

May I suggest silicone based lubricant spray instead of WD40, which can damage some plastics. I had an expensive experience some years ago with a stretched nylon tyre on a sliding door roller. I could only blame the stretching on contact with WD40.

I have had no issues with WD40 which is I believe silicon based, however it is always best to be careful if experience has proved otherwise.

 

[Stevetyphoon]

Hi,
Ok, so a bit nervous.
Just want to confirm though, that it is the white piece with the vacuum hose coming off at 90deg that comes out? Not the vacuum hose to pull out of the white bit?

 

[bugsymike]

Hi,
Ok, so a bit nervous.
Just want to confirm though, that it is the white piece with the vacuum hose coming off at 90deg that comes out? Not the vacuum hose to pull out of the white bit?

Yes the white 90 degree plastic bit is the one way valve and is pushed into the rubber grommet in the servo tank.
Do not try and pull the plastic pipe off the white plastic 90 degree bit as it will self destruct.

 

[Stevetyphoon]

Cheers Mike, I'm going in all guns blazing

 

[bugsymike]

Cheers Mike, I'm going in all guns blazing

No swearing.
Just WD40, gentle lever with a wide flat screwdriver and a bit of twisting after emptying the vacuum by pressing the brake pedal until hard..

 

[Stevetyphoon]

Ok Mike. Got the thing off. Actually quite surprised as to how much of a vacuum is created. Enough to leave a sucked out ring on my finger! If I've explained that ok.
What do you reckon?
Shame I can't send you a beer for your help! You're not in Devon by any chance!

 

[bugsymike]

Ok Mike. Got the thing off. Actually quite surprised as to how much of a vacuum is created. Enough to leave a sucked out ring on my finger! If I've explained that ok.
What do you reckon?
Shame I can't send you a beer for your help! You're not in Devon by any chance!

Regarding the earlier comment, I will leave you to explain what happened with the hoover.
Where do you think Torbay is? Here is a clue, though I don't have this car anymore, fixing the sunroof was enough for me.

 

[Stevetyphoon]

Ah, just been re-reading your wise words.
I didn't leave pumping the brakes for 5 minutes after switching the engine off. More like 1-2 minutes.
I'm going to give that a go next.

 

[Stevetyphoon]

We were in Torquay on Saturday visiting friends!

 

[bugsymike]

Ah, just been re-reading your wise words.
I didn't leave pumping the brakes for 5 minutes after switching the engine off. More like 1-2 minutes.
I'm going to give that a go next.

I have had cars with a good servo hold vacuum to the next day.

We were in Torquay on Saturday visiting friends!

Two of my daughters live in Torquay, I am in Paignton.