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Old 05-15-2018, 01:44 AM   #1
tintintin
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Default '93 940 Front Brakes on an '85 740?

Confused after reading the Brickboard FAQ on brakes. I have access to a '93 940 that's going to the JY soon.

Can I swap the bigger brakes from the '93 940 to my '85 740? Presuming I need the calipers, rotors, hubs(?), possibly struts? Anybody done this? The Bendix front brakes on mine have always been problematical for me. Now they are vibrating again, after a somewhat recent caliper rebuild.
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Old 05-15-2018, 09:50 AM   #2
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I suggest swapping in the complete strut assemblies from the 940. Then you’ll get the later, arguably better hubs and newer brake setup all in one go. Brickboard details how you only use one set of the front brake hard lines for the newer calipers. You have to block off the unneeded ports in the master cylinder, but otherwise it’s pretty straight-forward.
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Old 05-15-2018, 12:48 PM   #3
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Originally Posted by lverhagen View Post
I suggest swapping in the complete strut assemblies from the 940. Then youíll get the later, arguably better hubs and newer brake setup all in one go. Brickboard details how you only use one set of the front brake hard lines for the newer calipers. You have to block off the unneeded ports in the master cylinder, but otherwise itís pretty straight-forward.
Agreed. Entire strut assy, ignore the ABS sensors, pray the hoses work. Perfect time for top strut bearings and perhaps BJ & tie Rod ends.
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Old 05-16-2018, 03:15 AM   #4
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What about swapping the steering rack also?
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Old 05-17-2018, 04:14 PM   #5
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That will depend on what style rack is coming out and what style is going in. There were three styles and four brands (ZF, CAM, TRW, Kyoto) with power steering hose ends to match. If there isn’t anything wrong with your current rack, I would suggest leaving it.

If you’re set on swapping the racks too, just grab the power steering lines while you’re at it to ensure a straight-forward swap.
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Old 05-18-2018, 01:33 AM   #6
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If there isnít anything wrong with your current rack, I would suggest leaving it.
Agree, but it does leak at the input shaft, and it does something strange on curving freeway onramps, where minute corrections to the wheel feels like the assist cuts in and out. Actually, not cutting in and out, but going from normal assist to super extra assist. At first, I thought the front wheels were washing out, losing traction, that's what it feels like.

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If youíre set on swapping the racks too, just grab the power steering lines while youíre at it to ensure a straight-forward swap.
Good idea, thanks.
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Old 06-05-2018, 02:12 AM   #7
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Default Needed this done Yesterday!

Needed this done Yesterday! Damn Bendix brakes, again the shims had moved off the pads (after gluing them and making sure the locating tabs were tight to the pad backing!) and the one on the outboard pad had been carving a groove into the rotor (the part surrounding the bearings) until this afternoon, when braking for a downhill turn I felt something give and it just didn't feel right after that.


Took the wheel off to inspect and found the rotor sliced nicely in half, approx. 7mm outboard of the outboard rotor friction surface, as if it had been cut on a lathe!


Anybody can tell me what size plugs I will need to block off the unused ports on the MC? Really motivated to do this swap now and want to get the needed parts ASAP.

Last edited by tintintin; 06-05-2018 at 04:43 AM.. Reason: grammar, word choice, etc.
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Old 06-05-2018, 06:35 AM   #8
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Shoot a PM to Simon Babbs..... most expertise in the 7 series cars.

I'm not sure why you would need to block ANY lines; thought only the 2 series had dual hoses up front for the goofy calipers.

Also a good resource: 700/900 Volvo Club UK Maint. pages..... .google them and likely find your answers there.....
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Old 06-05-2018, 07:20 AM   #9
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Originally Posted by DET17 View Post
Shoot a PM to Simon Babbs..... most expertise in the 7 series cars.

I'm not sure why you would need to block ANY lines; thought only the 2 series had dual hoses up front for the goofy calipers.

Also a good resource: 700/900 Volvo Club UK Maint. pages..... .google them and likely find your answers there.....
1987 and earlier non-ABS 740s and 760s have dual lines to the front calipers, or at least my Ď87 740 sedan does, and my 1989 740 Turbo wagon with ABS does not.

As far as master cylinder port plugs, I donít know off hand for certain, but my first guess would be M10x1.0 thread since thatís what the hardline fittings are where they meet the caliper flex lines.
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Old 06-05-2018, 11:35 AM   #10
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If swapping racks, make sure to swap the tie-rod ends with the rack.
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Old 06-05-2018, 01:58 PM   #11
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What I did was cut one of the end plugs off of the brake line I didn't need or was removing and took that down to the Napa and they have brake line plug things. They look just like the line ends but are solid.

All the non ABS 740's have dual brake lines for the front calipers. I got this 91 740 NA with no ABS and it has dual front lines with Big Brake caliper and rotors. Jumbo's are the best stock ones of course. All the 940's have those and 740 starting in 91.

Yeah you'll need the struts from the 93 as the spindle is different bigger and better sealed bearing that you torque down real tight unlike the normal bearings that are finger tight. Seems to me the dual brake lines start at the junction box but maybe there are two from the master cylinder, but yeah unplug and put in plug. Everything just bolts in, all of the strut and the calipers and the rotors.

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Old 06-05-2018, 04:12 PM   #12
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Thanks, that helps me formulate my game plan. BTW, the lines for the LF caliper come from the junction box and the RF caliper lines come directly from the MC. Hope this mod does not affect the F/R brake balance.


Happy to hear that it's a relatively simple bolt-in swap with good benefits and the jumbo brakes are highly regarded.



Trying to include photos of the cut rotor for everybody's interest. Evidently photobucket is no longer a good solution?
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Old 06-06-2018, 04:41 PM   #13
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How important is it for the port plug to be a genuine "brake port plug?" None of my FLAPS, NAPA, Tacoma Screw, etc. have it. Can I use a suitable bolt?
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Old 06-06-2018, 06:11 PM   #14
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How important is it for the port plug to be a genuine "brake port plug?" None of my FLAPS, NAPA, Tacoma Screw, etc. have it. Can I use a suitable bolt?
I've used short/shortened M10x1 bolts with copper washer. Or you could just use a caliper nipple.
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Old 06-07-2018, 12:10 AM   #15
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Or you could just use a caliper nipple.
Do you mean a brake bleeder screw?
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Old 06-08-2018, 03:58 PM   #16
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In fact brake bleeder screws is what I used to plug the unused ports, because that's what I had on hand.


Regarding plugging the unused port (that fed the second line for the LF caliper) on the junction box: Is that what is lighting up the brake failure indicator lamp on the instrument panel every time I apply the brakes? Is is sensing an imbalance now?
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Old 06-08-2018, 04:07 PM   #17
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I've found that M10x1.0 thread is compatible with 1/8"-27 NPT pipe plug.
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Old 06-09-2018, 12:11 AM   #18
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I followed the procedure from the volvoclub.org.uk faq


https://www.volvoclub.org.uk/faq/Bra...9XXJumboBrakes


Bled the system, using almost 1 liter of DOT4, and now have braking only from the rear calipers, specifically the RR caliper. I measured the rotor temps after a downhill with my IR thermometer and the RR rotor was ~ 350degF, while the other 3 were ~130F.


Pedal feels hard, yet not powerful. IOW, it moves easily at first, then stops travel abruptly, as if there were a hard block under the pedal impeding further travel. The brake warning lamp comes on, and the RR tire skids.


Any ideas? I was hoping for a big improvement with those Jumbo brakes!


On the bright side, the alignment feels pretty close.
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Old 06-12-2018, 03:16 PM   #19
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Problem was self-imposed. During the switchover from 2-line front calipers to 1-line, I chose to plug the extra ports for the lines corresponding to the upper lines on each (former) front caliper. This ultimately created the imbalance of having 3 corners on one MC circuit (cylinder) and 1 on the other.


The FAQ I was following made no mention of choosing specific ports to plug, so I happily ignored it because trying to decipher that 8-port junction block buried down there below the fuel lines, vacuum lines, A/C lines and misc. wiring was making me dizzy. Should have been more careful to trace each line back to its source.


After moving the lines and plugs around and rebleeding, now I have braking at all 4 corners, and similar rotor temps. Not sure if I have entirely solved the RR wanting to lock up; more testing will tell.



I may end up swapping over the 93 940 MC as well (larger cylinders?), if I can figure out a way to get the hardlines to mate up with it.


Now that I have stronger front brakes I also get to deal with brake dive.


So far I haven't noticed any difference from the increased unsprung weight (larger brakes/hub/rotor).


Thanks to sbabbs who helped out with a generous PM correspondence.
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