vacuum pump diaphragm

[andydclements]

On e the way to work, approx 150m from my destination the brake pedal became very hard, brake warning light came on and I watched the temperature gauge expecting it to climb rather rapidly. It didn't! Having already decided it was either the belt lost tension or the belt wasn't there any longer (slipped off or snapped) I was prepared for a recovery truck return home this evening. Having worked quite late to catch up a bit, I decided I'd try and get as far as I could at low speed before the temperature got anywhere near too hot. I made it home, which surprised me.

This evening I started looking for the cause as the belt was fine, I could achieve and maintain vacuum using a hand pump attached to the T piece for the vacuum sensor near the brake servo. The pipes were obviously all attached, and the servo wasn't leaking lots of air. What could it be? It has to be the pump not working. I checked and the pulley was rotating, so I started to wonder about the rotational components in the pump having sheared, and proceeded to take the pump off (I hate that job, especially since the engine was still hot).

Having inspected the pump properly I discovered the outer steel bell cover was loose. I found the spring for the diaphragm was fine, but it still wouldn't pump air. Nothing for it, might as well remove the bell, which I did gently. I found the diaphragm had slipped and the lip that should be held securely by the bell was tucked up in the bell, thus no pumping. So now I have that wonderful job of trying to get the PITA back on the car.

Chance of that happening this evening seems remote at best. i think I need to clear the tools away and have a nice drink.

OH, as the S3 had sheared its oil cooler pipe and I hadn't had a chance to fix it I had to move it off the ramps, into the garage in order to get the TE onto the ramps. Do cars start getting jealous? Is that why both fail at the same time?

[andydclements]

Well, the temporary repair that was supposed to get done later in summer 09 lasted quite a while, Thursday the bolts holding the bracket for the pump to the water pump boss came loose and so the belt slipped off the vacuum pump pulley onto the body of the pump, usual loss of servo assistance and rapid temperature increase followed. I didn't know exactly what had happened, but with the symptoms it was going to be something like that, or the pump could have been ceased solid and stopping the belt.

Today I went and investigated, and decided I would deal with this once and for all, so most of the day involved fitting the Audi electric vacuum pump and altering the vacuum plumbing.

When it came to testing it, I wasn't impressed, the VAG pump could get 1 1/2 times the level of vacuum (60cm Hg) that the brand new mechanical pump could (40cm Hg), but couldn't deliver the volume of air movement needed to give a reasonable servo down time. Thus, new pump to be fitted, one problem, it didn't have the boss on the shaft and I was in no mood to pull the old boss off and try and press it on the new shaft, so I put the new pump bell onto the old casting, having checked the bearing was fine. I had to turn the inlet steel pipe through 90degrees to match the Lotus spec one, but for a

[neill1607]

I was going to post in the overheating thread I'd started, when I noticed this one.

Had to take the esprit out today as it was the only car left. As I was driving I noticed a subtle change in the feeling of the brake pedal, followed by a rise in temerature, followed by the brake warning light coming on. After reving the engine a few times the light went out & the temperature started to drop, brake pedal feel back to normal.

I was going to post to ask if there was a link between the cooling system & the vacuum system - obviously, from the comments in this thread - there is.

Do both the vacuum pump & the water pump run off the same belt?

[andydclements]

Belt loose, could be because the belt needs replacing or tensioning, or because a bracket has loosened from the water pump.

If the belt to the vacuum pump gets loose it means the water pump will not work effectively either as it is the same one.

[andydclements]

For those that want to eliminate the problem of the mechanical vacuum pump, here's the type of pump that should be suitable (it's from a big car which uses the pump for brake boost).

http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=110506238193&viewitem=&sspagename=STRK%3AMEWAX%3AIT

[Newts]

Hi Andy

I believe some diesel cars have a vac pump attached to the back of their alternator, do you think this would provide sufficient "suck" for an Esprit ?

[andydclements]

Yes, but....

Space is what stopped me going that route, there is not much room behind the alternator because of the plenum chamber location. Can be done, but may involve a lot of searching for a really short alternator with pump.