Hi all,
Next week-end my son and I need to perform some maintenance items on his 940 wagon and I had a few questions.
1.The brake warning would come on every few weeks and we had to add fluid. I traced the leak to the brake line junction block under the master cylinder so this needs replaced. Any tips on replacement? It looks slightly corroded so it looks like it would be easy to break a line while removing. I see a lot of PB Blaster being used here.
2.My second question is that I noticed the alternator belt was loose. When I tried to take up the slight tension I broke the tensioning crew. I did this on my 240 last year. I just use a breaker bar and pad and tightening it was no biggie. The 940 is on the top of the engine rather the bottom like the old 240 and no matter what I do I cant seem to get the belt tight. Any trade secrets here lol.!
We need to get this sorted out so sonny gives me my 240 back!
Thank you!!!!
Joel

get another bolt off a junker.

If you do not know what item you are dealing with, have the brakes done by a Volvo tech.

They can adjust the belt also - What looks like a tensioning screw is sort of a stop - it is too weak to move the alternator. You loosen everything up, adjust the alternator (using a NEW belt) and tighten the tension screw last - it just helps hold the adjustment.

The car should last several years - spend the money for great brakes.

Your son is worth it!

My daughter was hit in the driver's door in our '89 744 by a drunk driver running a red light. The driver's floor was just wide enough for her feet, the steering wheel was touching the roof. The tow driver thought a truck hit her. Her car was thrown 30 feet sideways and the other car was 100 feet away in a parking lot.

The hospital was a trauma center and the EMTs were sure she was injured - the ER X-rayed her legs and hips because they thought she was paralyzed. She and the other 3 teens in her car were un injured. The other driver got jail time.

Your post sounds like you should not do brake work.

Your son is worth the money.

"What looks like a tensioning screw is sort of a stop - it is too weak to move the alternator."

Not even close. That screws sole purpose is to supply the (very little) tension that an alternator belt(s) need to do their job. The lockdown bolt on that tension arm is what should be holding the tension and the pivot bolt being tight makes the job that much easier. Many of us actually back off the long screw 1/2 turn after everything is tensioned in case we even have to tighten the bolt in order to loosen it in the future.

To the OP, I used a 2 x 4 in one hand and speed wrench in the other to tension the alternator on my 940 until I found a usable long screw at a PnP. Remember, the goal is tight enough to not slip...nothing more...and retension after about 500 miles for belt stretch. You accessory bushing will thank you for it. By the may, how do those bushing look?

Hi Griff951,


Answer1:
The "brake line junction block" below the MC is the brake proportioning valve. This valve is to prevent the rear-end "fishtailing" in the event of hard braking. So it is a safety item. Both brake lines from the MC go to it. From the valve it would then branch out to the ABS control unit or straight to front/rear brakes (for cars without ABS).


First tip:
Try tightening all the brake line nuts at the valve first. Use proper brake line wrench. If tightening doesn't work then you might have to replace it.


Replacement tip:
The proportioning valve is quite expensive. Take your time to shop around. If you have Volvo parts dealer near you, you might get it at a reduced price - new old stock - as this part rarely gets replaced. I got my OE part at almost half price at my dealer. Otherwise getting it online (eBay/FCPEuro) is almost paying premium price. Another source is from pick n pull but you'll have to try your luck there.

There are different valve "rating" for wagon and sedan cars. I think this is due to different rear-end weight for each type of car. The wagon uses type 2 (stamped on the valve body) and sedan type 3. Be sure to get the right part.

Replacing the valve is quite easy if not for the slippery brake fluid. Rubber-gloved hands won't do - no grip. Use some cloth to get some grip on the brake line nuts to start them threading into the valve's ports. You'll also face some difficulty threading in when the hard brake line is not in perfect alignment to the port. Take your time here.

Reduce fluid drain from the brake reservoir/MC by covering the reservoir's refill opening with soft plastic (the one used to wrap food) and screw on the reservoir cap. Some recommend using sticky tape to cover the refill cap's vent hole but I find this not working. Anyway if the brake reservoir empties you'll have to bleed the MC after valve replacement.

In my experience I had to bleed the entire system. Again after one week. And again some more.


Answer 2:
Find a smaller breaker bar/rod which could fit underneath the alternator to leverage it upwards. Even this is difficult as you have to dismantle the air intake plumbing. Otherwise replace the broken adjustment screw (good for the long term). Get it from hardware shop. Worn belt (already thin profile) and worn bushings won't help too.


Regards,
Amarin.

Hi Amarin,

I haven't any experience with 900 series cars, only 240's. I'm a little confused with the terminology you're using in answer #1, and curious.

In the pre ABS 83-90 240 the junction block contained what Bentley calls a Pressure Differential Regulating Valve. It activates a warning light in the cabin due to loss of pressure in one of the hydraulic circuits. The non ABS 91's are odd in that this valve was removed from the junction block because the warning now came from the MC. It looks like this

https://www.ebay.com/itm/NEW-Volvo-Brake-Proportioning-Valve-VM395-1273052-240-242-244-245/132289530707?hash=item1ecd120b53:g:iJsAAOSwid1aApHU&vxp=mtr

It appears from this that the Proportioning Valve and the Pressure Differential Valve are one and the same on the 240. However I'm fairly sure that neither of these affect the rear wheels. The reduction of pressure to prevent lock up of these wheels on non ABS 240's is controlled by two valves bolted above the differential called, not surprisingly, Pressure Regulating Valves.

These valves are absent in this location on ABS equipped 240's. Your description seems to suggest they were combined into a single valve and moved forward into the junction block on both ABS and non ABS 900's.

If that's the case I can understand why it would be pricey. FCP has single regulating valves at $350. for the 240. I'm surprized though, because I thought that ABS, with it's speed sensors and electronic regulating capacity would have put those mechanical regulators out of work.

Sorry to ramble on, it's just a lack of daylight.
Peter

Hi Maplebones,

I think Art has answered the real identity of the eBay item.


"Your description seems to suggest they were combined into a single valve and moved forward into the junction block on both ABS and non ABS 900's"

They are different valves for different types of braking system our Volvo uses. Description as below:



The 900 series car uses front-rear split circuit braking system. In this configuration there is ONE brake circuit consisting of two front brakes and ANOTHER circuit consisting of two rear brakes. In case of hard braking the rear-end might get locked up too soon causing fishtailing i.e loss of control. So the "brake proportioning valve" is put there between front and rear circuits to prevent that. In short its about front-to-back brake force balance.

The 200 series car uses diagonal split circuit braking system. In this configuration ONE SIDE of the front brake is coupled diagonally with a rear brake i.e. a rear brake on the OPPOSITE side, and vice versa. In this system a "pressure differential valve" (i.e pressure difference between RIGHT and LEFT braking circuit of the car) ensures both sides are EQUAL for proper braking. In case of brake force imbalance during hard braking the car might "change lane" or goes sideways. In short its about side-to-side brake force balance.

The addition of ABS serves as an additional safety/control measure in both 200/900 series cars. Lets not forget the ABS (itself quite a complicated system having its own ECU, monitoring and activating systems) might break down during that inconvenient time.

So multiple safety redundancies are built into our beloved Volvos.


Regards,
Amarin.

Edit: I'm also not well versed in the 200 series brake. Art's recent answer seems to suggest that some 200 series car might be using the front/rear split system (rather than diagonal) for its ABS equipped cars. For the 900 series I'm quite sure the configuration is MC->brake proportioning valve->ABS->front/rear brakes (delete the ABS for non-ABS car). I got this from volvopartswebstore.com for the 900 series car.

Though the thread topic is not 200 series cars, I get that the Brake Failure Warning Sensor used in them may be somewhat unique across automotive designs for that era they were used. It isn't a "pressure differential valve" and it has no function within itself to keep the dual-diagonal circuits equal in pressure.

Alternate names for this which don't pervert its function are "Pressure Differential Switch," "Brake Junction Box," and more informally, octopus.

The Warning Sensor only alerts the driver to an imbalance, which might be caused by a seal or line failure in one circuit. An earlier version of the same sensor, or switch, was used in the 140 Volvo, which required reset once triggered. The 240 version returns to center by spring, and the sensor does not "valve" anything -- that is it does not affect brake pressure, it only measures the differential between the two circuits, before the rear wheel pressure reduction is done.

In 1991, ABS was optional in the 240 series. Those purchased with ABS have the same system used in your 940. The "brake failure" lamp is operated by a liquid level float switch in the reservoir. Those without ABS also got the float switch, and the Brake Failure Warning Sensor was replaced by a simple manifold, after which the two remaining years of 240 production received the ABS plumbing.

Here's a Brake Failure Warning Switch opened up. There is no fluid path between the circuits normally. That is unless the O-ring seals fail.


--
Art Benstein near Baltimore

SUCCESS:
At age 4 success is . . . not peeing in your pants.
At age 12 success is . . . having friends.
At age 16 success is . . . having a drivers license.
At age 20 success is . . . going all the way.
At age 35 success is . . . having money.
At age 50 success is . . . having money.
At age 60 success is . . . going all the way.
At age 70 success is . . . having a drivers license.
At age 75 success is . . . having friends.
At age 80 success is . . . not peeing in your pants.

Hi Peter,

The Brake Failure Warning Sensor is the correct name for the part listed on e-bay.

It is common to hear and see it called a proportioning valve, but that's misleading, and frankly wrong.

ABS uses a dual circuit master, but it isn't diagonal, it is split front to rear, so only one valve is needed to do what the two proportioning valves at the rear axle of the 240 did. It is up front below the master.

Edit: Also, I have little 900 experience, but I do believe there were not any non-ABS 9xx series cars, at least not in US market. Do you know if the non-ABS 940 was marketed in Canada?
--
Art Benstein near Baltimore

Grandchildren are God's reward for not killing your own children.

Dear Art Benstein,

May this find Well, You - and All with You. The parts list and diagram in Volvo VADIS - a superseded dealer parts/service database - shed some light on your questions.

VADIS differentiates between US and Canadian models. Thus, there a headlight switch for US models (#1362699, [NLA]) and Canadian models (#3515978). I do not see separate part numbers for "Canadian" and "U.S." brake system parts. That suggests non-ABS models were not supplied to North American dealers for 1993 and later models.

As to the part in question, that for sedans (#3546634) is called a "reducing valve"; that for wagons (#3546635) is called a "reduction valve".

Despite having different names, both parts look alike. Both have four "ports" or fluid-pipe connecting points. To two side ports attach fluid pipes from the master cylinder. To the top and bottom ports attach fluid pipes that go to the ABS hydraulic unit, on the other side of the engine bay (non-turbo engine). From the ABS hydraulic unit, fluid pipes go to the front wheel brakes and to the rear brakes.

This plumbing suggests a pressure adjustment for front-rear weight difference (as between sedans and wagons) is made within the ABS hydraulic unit. It is possible that the diameter of fluid channels inside the valve are different as between sedans and wagons.

Hope this helps.

Yours faithfully,

Spook

Dear Amarin,

Hope you're well. This excellent write-up should be added to the FAQs!! Few have done this work, as best I recall from posts dealing with brake issues.

Having your detailed guide in the FAQs will surely save someone much time and aggravation. Pls. see the FAQ page for the pathway to get it included.

Yours faithfully,

Spook

Thanks Spook! Hope you're well too. I'll see where I could add this in the FAQ.

Regards,
Amarin.

Dear Amarin,

Hope you're well, and you're welcome!

On the FAQs "Intro" page, there's an e-mail address, to which submissions should be sent. The site's secretary maintains the FAQs, so he's the "send to" fellow.

Hope this helps.

Yours faithfully,

Spook

Amarin's response deserves the thumbs up. It is clear this is help from someone who's been there and done that, and done it well.

I have nothing to add to this excellent walk-through of replacement. My only excuse for posting here, is the chance the proportioning valve diagnosis is hasty. I say that from recent experience of my own, where the owner of the car was quite convinced the valve was the problem, but instead it just represented the last place on the car for the brake fluid to collect from a leaky master reservoir. The plastic reservoir was cracked at the outlet port -- a much easier fix indeed. This was a 240.

Again, it is rare to see such a clear guide to brake line work, especially the point about getting the nuts started in all that fluid. Kudos!
--
Art Benstein near Baltimore

You spend the first two years of their life teaching them to walk and talk. Then you spend the next sixteen telling them to sit down and shut up.

Thanks Art!

Now that you've mentioned it, I admit it is a bit hasty diagnosis. I do hope the fix could be something simpler for the OP ; )

Regards,
Amarin.