Replacing P38 Brake Pads &Rotors

Reassembled brakes

Introduction
Tools needed
Brake Pad Removal
Rotor Removal & Replacement
Caliper Guide Pin Check/Recondition/Replacement
Installing the New Pads
Links to Related Information


Introduction

Range Rovers are notorious for wearing through the brake pads rapidly, and new ones are expensive (last time I checked, in October 2004, the dealer wanted over $180 just for a set of front pads!!). If you get the job done at the dealer, I find they almost invariably tell you the rotors are worn down below spec, and need to be changed also. These are another couple of hundred dollars per axle set for the parts. Add to that a couple of hours of labor per axle and you are in for a good sized bill. However doing the brakes yourself is not difficult, and if you get the parts at aftermarket sources you can end up saving a lot of $$. For example, I replaced the front pads and rotors, and the rear pads only, for a total of $179 worth of parts from Atlantic British. The same job would have cost me about $700 at the dealer including genuine parts and labor.  If you do the job yourself, as often happens there are a few tips that are not mentioned in the shop manual. Especially, as often happens, there are some operations where the manual is a bit cryptic.  This page is an attempt to make the job easier and save time for the do-it-yourselfer. I would like to thank  David Sparkes, Scott Kirn, Adam Moore for help with this page. Additional information and photos from Kevin Kelly, whose approach to these things is far more meticulous than mine,  were particularly helpful in supplementing my own experience. Photo at top: Right front brake with new disc (rotor) and pads installed.

Tools Needed:
Basics:
12 point socket set with a long handle/breaker bar
C clamp
Jack (and preferably axle stands for safety)
Hammer (if changing rotors)
Impact driver (if changing rotors) with PoziDrive bit (Phillips bit is close but may damage screw head)
Anti-Seize compound
Liquid Wrench Spray (if rotor is rusted to the hub)

Optional Tools & Items for Meticulous Mechanics and to Prepare for All Contingencies:
6-point 1/2" metric socket set
Click-type Torque Wrench
Combination Wrenches 10mm to 15mm (if brake line blocks socket on caliper bolt)
LockTite
Brake Cleaner
Small Wire Brush
Syringe or Turkey Baster (to extract excess brake fluid from master cylinder)
Brake Hose Clamp/Line Lock/Hose Clamp Pliers
Brake Fluid Hose
Bleeder Screw Wrench 
Dremel Tool or Screw Extraction Kit in case Rotor Screw head is destroyed
 
Parts Needed:
Front and/or rear sets of pads and rotors (see P38 Parts Sources page for best deals on these).

Rotor Set Screws (two per axle).
Land Rover part number SF108201. Scott Kirn did the job based on the info on this page and reports: "I would spend the couple extra dollars and buy new rotor set screws. If yours aren't already in horrible condition, they will be by the time you get them out with the impact driver. Best to be safe and have new ones ready to go. You can leave the screws out and then just put them in later, but you would need to take the wheels off again, and I don't know what problems (if any) you would have driving without the set screws." Kevin Kelly paid $3.08 each for the screws at the Land Rover dealer in October 2005.

A caliper guide pin kit is also a wise precaution in case you find (like I did) that some of yours are frozen.
Atlantic British has them for $28.95 (front axle set) and $26.95 (rear axle set) including new pins, rubber boots and special lubricant. At least, get some caliper guide pin grease (brake grease) to lube the old ones.

Preparation
Adam Moore reports "I heated up the brakes driving the car around to gather the required pieces for the job. I got home and immediately washed the car including the wheels and tires. This made the job a lot cleaner and I think also served to loosen up some of the components as the hot - cold cycle can do that". Kevin Kelly just uses spray-on brake cleaner to clean each rotor and caliper after removing the wheels.

Brake Pad Removal
After removing the wheel, you are presented with the view shown in the photo below left. To get at the pads, you have to move the caliper out of the way. It is held on by two 12 mm (front) or 11 mm (rear) bolts which engage with the caliper guide pins. The bolts are unfortunately on the inner side of the assembly, but are not hard to get at (their positions are indicated by the arrows in the picture below at right). Kevin Kelly observes that many brake pad manufacturers supply new caliper pin bolts with each set of pads, so the bolt heads may not always be the same size. They will probably be 11mm, 12mm or 13mm.  Also, Some mechanics use Lock Tite on the caliper bolts, so you may need a lot of force to remove them -- I had no problem with mine but Kevin needed a breaker bar for leverage on his, and used a 6-point rather than 12-point socket to avoid rounding the heads.

brakes exposed

Removing piston assembly

Right front brake shown after removing wheel on author's 4.0SE. Note badly scored rotors.

Arrows indicate positions of bolts holding the caliper piston assembly to its guide pins.


If you are only changing the pads, you can just remove one of these bolts, and as long as the other guide pin is not frozen up you can swing the caliper back out of the way. (Photos below).

Hinging the caliper back

Hinging the rear caliper

Hinging the caliper out of the way to expose the pads on the left front brake. Manual recommends removing bottom guide pin bolt and hinging from top; hinging from bottom is easier but take care not to strain brake hose.

Hinging the caliper up to expose pads on left rear brake.  Brake hose is too short to allow hinging from bottom. Note rear calipers have only one piston each.


If (like me) you are also replacing the rotors, it is easier to remove both bolts completely and get the caliper out of the way, resting it on a convenient part of the steering linkage. In either case, the pads are now exposed, and can be lifted out (photos below).

pistons aside

pads removed

Caliper piston assembly  lifted off and moved aside to expose pads. Be careful to support the caliper so it won't fall and strain the brake line. Note springs on pads which are compressed by the caliper casting to hold them firmly in place.

Pads lifted out. Note the carrier for the pads and calipers straddles the disc rotor and still has to be removed if you are changing the rotors as well (see below).


If you are not replacing the rotors as well, you can now skip ahead to "Installing the new pads" below.

P38 Brake Rotor Removal & Replacement
Removal of the old rotors is not quite as easy as the shop manual would have us believe. After removing the brake pads, the caliper mounting frame still straddles the rotor and has to be removed. To do this, remove the two bolts that hold the mounting frame in place on the hub. These bolts are in an awkward position behind the hub (see photo below left); doubtlessly they are easy to access if you are a Land Rover dealer with the vehicle up on a lift. The shop manual describes removal with the caliper piston assembly still attached to one of the guide pins, but access is much easier if you have removed the caliper piston assembly completely first  as described above and pictured here. (There is only one more guide pin bolt to remove). For the mounting bolts, you need a 12 point socket and a fairly long handle to get enough leverage with the awkward angle when accessing them from the outside. It may be a metric bolt but a 3/4 inch AF socket works fine for the front (so does 19 mm), and a 1/2 inch AF for the rear.

View from inside wheel well

Location of screw seccuring rotor

View from inside wheel well looking out, with caliper removed. Arrows point to bolts holding carrier for caliper and pads. These have to be removed to get the rotor out.

View of exposed rotor after removing caliper carrier. Arrow shows location of Phillips screw holding rotor in place. An Impact driver is usually needed to get this screw out.


Each rotor is held in with a very large PoziDrive screw, that looks a lot like a Phillips screw (see photo above, center). In the shop manual it merely says: "Remove screw securing disc, remove disc". However in real life it is not quite that easy, and a standard screwdriver is no match for this one. The brake rotors go through tremendous heat cycles and the screw gets stuck very tightly. The best way to remove it is with an impact driver (picture below), which you just hit with a hammer. If you buy an impact driver from any reputable tool supplier, it will come with a selection of screwdriver bits, one of which will be sure to fit. Some will also accept 1/2"" drive sockets. I purchased an inexpensive but sturdy one at the local Ace hardware store for $11.95. Another example is the Sears Craftsman item #00947641000. Kevin found a standard Makita driver drill got his front screws out fine, but the heads on the rear ones were stripped so he cut slots in them with a Dremel tool and used a wrench on the end of a big standard screwdriver. A Craftsman Screw-Out Damaged Screw Remover Set (Sears item #00952154000) is another method for removing damaged screws.

Once the screw is out, the brake rotor can be pulled off. Neither I nor David Sparkes had trouble getting ours off, but some owners have and David reports that this can happen if there is a build up of rust inside the 'bell'. This won't allow the hub flange to slide through it. Having been faced with this problem before, David has three approaches.  The first is to hit the inner face of the disc, then rotate the disc / hub 90 degrees, then hit it again. Repeat again and again. As you can normally only get a decent hammer swing at one point, moving the disc has the effect of applying force all the way round the disc. The disc surface is damaged by the hammer marks, but you will not be re-using it. Kevin had some rust inside the front rotor that would not budge even after a lot of banging, so he used spray Kroil from Kano Labs http://www.kanolabs.com/ (a liquid wrench type penetrating oil popular with Series Land Rover Owners) which loosened them up.

The second method is to grind or hacksaw a slot through the disc towards the bell. With an angle grinder the heat and vibration probably help, but the main effect is the release of stress in the disc. The slot gets wider, and before you reach the bell the disc becomes loose. A third approach is to apply heat to the bell, which will loosen the rust scale on the inside. Alternately heat and hammer the bell hot spot, which should shock the scale off. Then hammer the disc as in the first method above.  The grease in the hub, and the seals, is the 'danger spot' when applying heat to the disc. Providing you don't heat the whole thing up to cherry red (or anywhere near) you should be OK.

Pizi Drive Screw

tools

new rotor

Close-up of PoziDrive screw that holds the disc rotor on the hub, and Kevin's PoziDrive bits that differ slightly from Phillips in having a flatter end.

Impact driver I used to remove rotor securing screw, and a tube of anti-seize compound to use on threads to make screw easier to remove next time.

New rotor installed, ready for caliper carrier to be put back on.


Putting the new rotor on is extremely easy -- just slide it over the hub and secure it with the screw (see photo above right). However, make sure the inside is clean and you don't get any dirt behind the rotor so it can't bed down properly, otherwise the wheel could end up being out of kilter when you put it back on over the brake rotor.. Putting anti-seize on the screw threads and the hub spigot before reassembly will help prevent a recurrence of any difficulty you might have had getting the parts off.  If your hub was rusted up like Kevin's, clean it up with a wire brush before applying anti-seize and putting on the rotor.

Put the caliper/pad carrier back on and torque up the mounting bolts to the hub (165 N-m/122 lb-ft front, 100 N-m/74 lb-ft rear). Because the bolts are facing into the wheel well, the display on my torque wrench is invisible without a mirror so I just tightened the bolts as best I could. Kevin use a click torque wrench so he didn't have the same problem. These are one set of bolts you don't want to work loose and fall out! Kevin recommends using a Lock Tite type thread locking liquid on them.
 

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Caliper Guide Pins (Checking/Reconditioning/Replacement)
Since the fixed end of the caliper needs to move sideways (inwards) as the pads wear down, the guide pins to which it is mounted (photo below left) are designed to move with it. These also need to be pushed back in (towards the outside of the vehicle) so the calipers will fit back on over the new pads. The pins are supposed to move freely but I found a couple of mine were a  bit stiff and had to be forced back in with a C clamp. What I should have done is replaced them or at least removed, cleaned and greased them and their guides. This should be done even if they are moving freely -- you can get brake grease (or caliper pin grease) at any auto parts store.

I made up for my sins another day, when I replaced the caliper pins using a caliper guide pin reconditioning kit (see photos  below). I shopped around and found complete kits were available at Atlantic British for $28.95 for the front axle (STC1920) and $26.95 for the rear (STC1910). Search for key word "caliper" on their site under Range Rovers, the kits will come up.

Caliper Guide Pins

Old Guide Pins

Guide Pin Kit

Inboard view with caliper removed; arrows show guide pins with rubber boots connected to guides in the caliper carrier to avoid dirt ingress.

Old guide pins with rubber boots still attached. Note threads inside ends for guide pin bolts. Note also flat edges on two sides of head; you need to line these up properly when replacing them. 

Guide Pin Kit STC1920 for front brakes (photo courtesy of Atlantic British).
For $28.95, this kit includes everything required for both front brakes, including brake grease to lubricate the new pins.


The pins should be easy to pull straight out, disconnecting the rubber boot from the back of the caliper. If they are stiff, that means they really need replacing! One of mine was quite hard to remove and had to be persuaded with a hammer.

(Note:
If you are doing the guide pins as a separate operation like I did, you don't have to remove the pads. You can just undo one guide pin bolt (12 mm) at a time, and hinge the caliper out on the other guide pin as above, but only far enough -- maybe 10 degrees -- to allow access to the guide pin and the hole (guide) it goes into in the caliper. This leaves the pads in place and makes for easy reassembly).

After removing each pin, I tried to clean all the gunk out of its guide with a screwdriver and a small piece of rag. Then I attached the new rubber boot to the guide (it stretches easily over the lip provided), greased the new pin with the special Lucas brake grease provided in the kit, and slid it in. If you push the pin in fairly hard the rubber boot will seat itself back on the new pin automatically due to the lubricating grease; otherwise pry it over the lip on the pin with a small screwdriver.

One of the photos below (see the left photo at this link) in the section on replacing the pads shows another view of one of the guide pins after it has been pushed back in so it will line up with the caliper when you put it back on. You can see in this photo that the guide pin must be oriented so its flat side is against the caliper casting. This stops it rotating when you tighten up the caliper guide bolt.

Installing the New Pads
Pushing the Caliper Pistons Back In
Before the new pads can be installed, the caliper pistons have to be pushed as far back into their cylinders as they will go, to make room for the thickness of the new (unworn) pads. Land Rover has a special tool for this -- "Piston Clamp LRT-70-500" -- but I find an ordinary C-clamp (G-clamp) works fine -- see picture below left. However, be careful not to damage the rubber dust boots while doing this. In fact, it is best to avoid direct contact between the caliper piston and a C Clamp (you can use the photo I attached).  Using a clamp on the edge of a piston often causes it to turn slightly and bind up (putting stress on the square cut seal inside the caliper). Make sure there is enough empty space in your brake reservoir so it doesn't overflow when you push the pistons back in. (I usually loosen the lid on mine to let the air escape). If you have topped up your brake fluid recently you may need to get rid of some with a syringe or turkey baster.

Compressing the caliper pistons

Protecting caliper piston

Guide Pins

Whether the caliper is removed and resting on the axle, or just swung aside while still attached to one guide pin, you can compress the pistons with a C clamp.

Ideally before applying the C clamp you should cover the piston to avoid damaging the seals, and to get a straight push on it with the clamp.

Kevin Kelly kindly supplied this photo (you can tell it's not my RR as it is too clean!!)

Repeat view of caliper mountings from inboard; arrows point to caliper guide pins reminding us they will need to be pushed back so the caliper will line up with the new thicker pads.


Kevin Kelly suggests a more careful method than my somewhat cavalier approach. To avoid damage to the caliper pistons and rubber dust boots, you can put the old worn brake pad over the piston(s) and use the clamp on top of the old pad (see photo above, center). If you keep the pad on top of the two front caliper pistons you will avoid having one piston pop out.

Adam Moore has an alternative method for this operation: "At the advice of Bill at Motorcars LTD I used the bleed screw rather than force the fluid back into the reservoir when backing up the pistons. This is slightly messy but very easy, and less trouble with one piston coming out while the other is being pushed in. I used a large C clamp for this operation and used the spent brake pads as a pad to push on the piston, worked well."  Using the bleeder screw risks letting air into the system (a line lock or clamp reduces this risk), while not using it risks getting contaminants in to your brake system (however the risk is low if you have your brake fluid replaced on a regular basis as recommended in the service schedule).


Pad Installation
Kevin recommends cleaning the pad mounting area with a wire brush before putting the new pads in. I have not tried this, but it can't hurt. Note that the genuine pads are chamfered on the leading edge (towards rear of vehicle) to help stop squealing. Scott Kirn reports that his new Ferodo pads also came with the leading edge already beveled. "It seems to work, 'cause my brakes are squeal-free."  Everyone has a different theory about how to stop disc brake squeal, but I was using aftermarket (Lockheed) pads that were not chamfered, so I decided to put some anti-squeal compound on the back of the pads before putting them on (the gooey red stuff you can see in the photo below right and at the top of this page). Kevin Kelly also used Lockheed pads and easily chamfered the leading edge of his pads with a quick rub on the concrete sidewalk outside his garage.

Lining up the caliper

lining up the mounting holes

During reassembly, the caliper might not quite meet up with the mounting bolt holes due to the force of the springs on the new pads.

Application of force such as another C clamp may be needed to press the caliper into position so the mounting holes line up.


The caliper can now be put back on its guide pin mountings. If you only removed one guide pin bolt, just swing the caliper back into position. If you took both off as I did, just put one bolt back in and  swing the caliper back into position. On one of my front brakes I found I could not exert enough force by hand against the springs on the new brake pads, which are pushing against the caliper casting, to get the second guide pin lined up. Here I resorted again to a C clamp to pull the caliper into position (photo above right). You can then tighten up both guide pin mounting bolts (recommended torque is 26 N-m/19 lb-ft for the front brakes, 35 N-m/26 lb-ft for the rear).

Done! The situation should now look like the picture at the top of this page. You are now ready to put the road wheel back on. I usually put anti-seize on the hub spigot as recommended in the owner's handbook so the wheel slides on and off easily. I also put a dab on the lug threads, but Kevin alerts us that his is not wise as the nuts might easily work loose, especially if they are only torqued up to the spec. He does feel it is a good idea to put some on the flat area of the wheel that touches the rotor since with all hub centric wheels you want to make sure that they slide in to dead center. If you replaced the rotors, be careful to use the star pattern and slowly torque the wheel nuts down since you will also be seating the rotor on the hub. You are now ready to put the road wheel back on.

Reassembled brakes

New disc and pads in place, ready to put road wheel back on.


Bedding in the New Pads

That's the end of the job for me, but serious drivers of fast cars always "bed in" the pads and rotors when they are renewed. This deposits an even layer of brake pad material on the rotors. Here we are fortunate in having the advice of long-time BMW enthusiast Kevin Kelly, who recommends slowly warming up the brakes and then doing a half dozen or so 50 to10 mph fast stops (you should feel the ABS kick in each time) to get the brakes real hot (you should smell the brakes) then let them cool slowly (drive for at least 10-15 minutes without stopping or using the brakes). You want to heat up the brakes without "overheating" them so if you feel the brakes starting to fade after the fifth 50 to10 mph stop you are done. It is important to find a place to do this that is safe and where you will not get stuck in traffic or have to stop at a red light before you let the brakes cool off. 

For more than you ever wanted to know about bedding in new brake pads go to the links below (and remember that the "stock" vehicles they are talking about in the articles are things like the BMW M5 and 911 Turbo so don't try and do ten 60 to 10 mph stops in a row with a stock Range Rover):
http://www.stoptech.com/tech_info/wp_bedintheory.shtml  and http://www.stoptech.com/tech_info/wp_bedinstock.shtml
The brakes should be ready to go after a single pad bed-in session, but you will probably benefit from doing this two days in a row. Just make sure you have enough time to fully cool the brake system before parking.


Related Information
For aftermarket brake parts sources see the P38 Brake Parts section of the Parts Sources page
For other brake repairs, see P38 Braking system section of the Repair Operation Details Page

 

 

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Page revised February 9, 2012