Little vacuum / hard breaks

Hi all, I’ve had some braking issues, and from what I can see it’s quite a common fault. I originally suspected the booster as the issue but noticed the vacuum (when disconnecting the heater line) was very poor. So I then thought vacuum pump... Today the vacuum pump has been replaced and still very poor braking, I was not impressed, as it was the best part of a days labour, and quite an expensive part that obviously didn’t need changing. Has anyone else had any experience of this and can anyone offer any advice on the next step I should take!?

 

Have you checked the other usual suspects like brake fluid level and brake cylinder leakage?

 

No I haven’t actually, thank you. Well my fluid is filled to max, but I haven’t checked for cylinder leakage. I’ll have a look in the morning.

 

"Braking issues" and "poor braking" can mean different things. Inability to stop? Brake pedal goes to floor when brakes applied? Brake pads worn, glazed or contaminated? Rotors rusty, scored or irregular surface? Calipers frozen? Brake lines corroded or leaking? ETC ETC

 

Sorry, bad explanation. If I start the truck up with my foot on the brake pedal it goes down after around 15-20 seconds very slowly. When driving it does stop but the pedal is very firm and gets firmer if I have to brake a few times in a row, until the vacuum has built up again. Pads and callipers are all fine, and I’m pretty sure there’s no leaky lines.

 

How old is your brake fluid? The master brake cylinder could be failing.

 

Brake fluid is pretty new and looks very clean, and at a good level. Thanks for the advice i’ll Check the master cylinder over.

 

A good start to figuring out the vacuum issue would be to get a reading from a vacuum gauge.

 

I don’t have a vacuum gauge unfortunately, however I have disconnected the hose and put my finger over the end and I can tell you the vacuum is barely noticeable, in usual circumstances it should hold against my finger very firmly. I have ordered a new booster anyway as I’m fairly sure that’s the issue, if not then it’s back to the drawing board.

 

A bad brake booster with a leaky diaphragm, can stall out an engine when idling. If you suspect the booster, just disconnect it.

 

Okay that sounds interesting, can you expand on this at all? So do you mean if I disconnect it when idling it should stall if faulty? Sorry not 100 % sure what you meant. Thank you

 

Disconnect the vacuum line into the brake booster and plug the hose end as not to lose any vacuum. If there is a leaky booster, the vacuum should be restored. It will indicate so by using a vacuum gauge before and after. The brake pedal will be pretty stiff without the vacuum assist, but still usable.

 

Okay so, I have now replaced the booster and the vac pump and still have the same issue!! This is getting very frustrating now! What would any of you do for the next step? I don’t know what else there is to replace? I’ve spent more than I paid for the truck trying to get brakes!! Haha. Someone please help. Pedal still very firm, is it just something I have to live with? Can a thicker engine oil create a better vacuum in the vac pump? If I start it up and it idles for a few minutes the pedal feels nice and easy to press, but just that one time, then it’s firm and slow at stopping. Trying to give as much detail as possible. Is this a common fault?

 

The CRD versions have an independent vacuum pump, and do not affect the engine operation.

(the petrol versions get their vacuum directly from the intake manifold, so will cause them to run rough/stall)

 

You seem to have been given misleading information, here.

I'm having this same sort issue with my 2007 CRD.

How did you fix your problems?

If the wheel and master cylinders all function normally while the booster has vacuum, then the hydraulics should not be the problem.

With the main hose from my Vacuum pump connected directly to a gauge, it shows it pull the vacuum straight down below 25 in Hg, so the pump is OK.

With the main vacuum hose reconnected to the Power Booster Check Valve and the Gauge connected to the smaller port of the Check Valve it shows a slowed rate of drop in vacuum. If you wait, with engine idle lifted to about 1500 - 2000rpm, the vacuum will drop slowly, the if the engine is switched off, the vacuum remains, so the booster has no internal leaks.

I now suspect that the Check Valve has internal issues, that are restricting the ability of the pump to restore the vacuum in the power brake booster and the other vacuum operated systems for the dash vents and turbo boost.

Do these "Power Booster Check Valves" have a history of failing?
As the original part listing in Australia was deleted in 2019, does anyone know of an aftermarket valve?