Volvo Broms valve

Hi from Downunder,
I am having problems with the Broms valve on my F7.
It occasionally clicks in like it should, but mostly has to be pushed in quite hard & held for a while before the maxis are released.
I’ve replaced the non return valves on the tanks, fitted a new four way valve (when it stopped filling the rear tanks) & replaced the broms valve (when I couldn’t pull the old one apart) but the problem persists.
Frustrating thing is that sometimes it works okay when all the tanks are empty & I startup & yet other times it does not.
Any clues?
Cheers
Ron

I could be wrong here, but Iirc the button would only go in when you had enough air built up, so no air meant the button would not stay in, start up and build the air up and in she would go, so I would be checking the pressures when the governor cuts in.
The governor is adjustable.

What are you doing with an F7 anyway? I havent seen one for years now.

Trickydick:
I could be wrong here, but Iirc the button would only go in when you had enough air built up, so no air meant the button would not stay in, start up and build the air up and in she would go, so I would be checking the pressures when the governor cuts in.
The governor is adjustable.

What are you doing with an F7 anyway? I havent seen one for years now.

Must be still using these in Australia going by the clues in the op.

I agree, it sounds like the air is building up too slowly or the compressor is cutting out too early. Have you put air gauges on the air tanks to check the pressure in the tanks when the button won’t go in? What do the air gauges on the dash say? I seem to remember you need in excess of 6 bar pressure before the button will push in.

Gauges indicate pressures are okay. Both systems build up to pressure & the low pressure buzzer cuts out. Once the broms is in & the truck running brakes work fine.
The curious thing is that occasionally it will work as it should, but there doesn’t seem to be a consistent set of circumstances when that happens.

We use the truck to cart around heritage machinery & have just last year put it on heritage rego. Down here this allows us to run the truck at Club events for a much cheaper rego.

Iirc theres 4 air tanks but only 2 gauges? if so might be worth checking the actual pressure in each tank on their own, dont forget just because a componenet is new means it actually works correctly!
Im sure the governor was a quite a comon issue but Im probably remembering the later models.

Ps the truck looks good, must be 30 yrs since I last worked on an F7, then we got posh and went to the FL range :grimacing:

Theres a couple of diesel mechanincs facebook pages that might be worth commenting on as Ive seen a few replies suggesting to me theres quite a few pople out there who still know how to fix the older Volvos.

Hi Trickydick,
Thanks for your interest & comments.

I have not measured the tank pressures separately, not sure where I can do that. The gauges on the Fr & R tanks seem okay as I did replace them with another set a while ago. All the tanks seem to have plenty of pressure when I drain them after a run.

There does seem to be air on both sides of the valve, but I will try to get a pressure ready there.

I’m not into facebook, but do you have a link to the diesel mechanic forums you mentioned? I may be able to convince my better half to check it out!

Here is a shot when we fitted the crane & new tool boxes in 2013.

Cheers

Here is the page, I think they ask you some silly mechanical question to make sure you are not a robot, if no go send me your details and I think I can introduce you and you get in straight away, Im no expert but ask your good lady and she might know how it works, becasue I just make it up as I go along!

facebook.com/groups/834543596616966/

We’ll start at the beginning.
Broms is Swedish for Brakes.
The valve which people refer to as “the broms brake” is a really valuable aid to safety which should be fitted to all trucks.
As the OP, and other, older drivers will know, the button in the truck would pop out whenever the air pressure dropped below a predetermined level. Usually this happens when the truck is parked for a while and the pressure drops gradually.
This will happen whether or not the handbrake is applied, and in the case of handbrake not applied, the spring brakes will be applied. Whether or not the handbrake was on, and regardless of the position of the handbrake control lever, the handbrake cannot be released until sufficient air pressure has been raised by the compressor to allow the the button to be pushed home. This means that for the handbrake to be released, the driver is required to be in the cab to push it.
How many times has it happened that we go to a standing truck, find that there is insufficient air pressure to release the handbrake, so go away, leaving the engine ticking over and the H brake in the off position, only to then see the vehicle roll off down the yard? I’ve done it. A chap I knew wasn’t so lucky and was crushed to death by his own truck. Had it been a Volvo it couldnt have happened.

As to what’s wrong with yours, I’m sorry I don’t know. I never heard of these blocker valves giving trouble so it may be an air pressure issue.

(I think the F10/12/7etc were the first Volvos to be fitted with that device. I had an F86 which didn’t have it, but it did have a very exciting feature which was that it pressurised the handbrake tank before any other, making it possible to set off in the morning g with no footbrake at all for the first few hundred yards.)

Old John,
Thanks for the input.
I agree the valve is a good safety feature and should be on all trucks.
My truck is not running at the moment as I am working on the power steering, so I pumped the air up from the workshop compressor. What I have found is that the park brake reservoir is taking a long time to fill. Once it is full the valve works as it should.
I need to check this out when the truck is running again.
I have been trying to release it when the gauges indicate the tanks are full, but the park tank is obviously not up to pressure.
Cheers

Yes, I think the park brake tank being last to fill will be the cause of your symptoms.
Maybe, having made the F86 park brake tank pump up first with the effect I have already described, Volvo, wisely, altered the bias on the F7!!
Anyway, treat her like a mature woman, just massage the button gently for a while and everything will slide into place. :smiley: