Tech Stuff

Sponsored by
Tips From Techs: Our Annual Advice Column Written By Technicians On the Front Lines

Aftermarket electric vacuum pumps are readily available. This one is from Comp Cams.
<p>Aftermarket electric vacuum pumps are readily available. This one is from Comp Cams.</p>


If you have a Chrysler PT Cruiser that has a code for insufficient EGR flow (P0401), don’t automatically assume that you’ll need to replace the entire EGR assembly.

Connect a hand vacuum pump to the EGR. With engine idling, pump vacuum. If you see the EGR valve moving inside its housing and the idle roughens up, the EGR is flowing. The culprit is likely the EGR’s black plastic actuator that is plumbed to the EGR valve. In the majority of cases, replacing only the actuator will solve the issue.

Larry Ritz, Smitty’s Auto Service, Dolyestown, Ohio

The pump is plumbed directly to the booster.
<p>The pump is plumbed directly to the booster.</p>


If you encounter an older vehicle (restoration, etc.) and/or an engine with a radical camshaft and the engine is not producing enough vacuum to operate the brake power booster, a remedy is to consider installing an electric vacuum pump. This eliminates the vacuum hose connection from the engine to the booster. Instead, a vacuum hose connects directly from the electric pump to the booster.

We recently ran into a 1968 Mopar where the engine was only producing 13 inches, which wasn’t enough to operate the booster. The electric pump creates 18 to 21 inches and worked out great. The only downside is that the pump can be a bit noisy when the ignition is initially turned on, but once the engine is running, the noise really isn’t that noticeable. Rather than getting into the engine to change the cam, this is a relatively easy and less expensive fix.

Brian Carruth, Image Auto, Lodi, Ohio


When dealing with a Corvette in the 1980s realm, be aware that the frame is made of fairly thin high-tempered steel. If repairs are needed, or if the customer wants to add frame stiffener bars, avoid welding to the frame, as this can weaken the temper of the steel.

Chuck Gray, Chassis Unlimited


If you run into a VW Passat where your scan tool can’t communicate with the system, chances are one of two problems are present: installation of an aftermarket radio or a bad ABS module (evident when the check engine light and the ABS light are both on).

The factory radio ties in with the ECM. If the K ground wire isn’t connected, a scanner won’t be able to communicate. By the same token, if the ABS module is bad, your scanner won’t be able to communicate with the OBD-II system.

Before going further, try disconnecting the ABS module and see if your scanner will communicate. Or disconnect the battery and let the system drain off any residual power, then try.

If you determine that the ABS module is at fault, rather than replacing this pricey item, you can have it rebuilt by Module Masters (www.modulemasters.com) for about $150 to a couple hundred bucks, depending on the specific module version.

Rob Holland, Holland Car Care


When servicing a GM LS engine (LS or LQ series), be aware that the flywheel bolt holes on the crankshaft flange are open to crankcase oil. Before installing the flywheel bolts, apply a thread sealant to the bolt threads to eliminate oil seepage. This is easily overlooked and can be mistaken for a rear main seal leak.

Brian Carruth, Birchwood Automotive


If a vehicle is equipped with a “posi” or “limited slip” rear end, and the customer complains about an annoying clicking or ratcheting feeling when moving in reverse with the steering wheel turned, there’s a very good chance that someone has recently changed the differential fluid and has not added the required friction modifier.

Drain about a pint from the diff, add one bottle of friction modifier and top off. Drive the vehicle for a few days and see if that makes a difference. If the ratcheting goes away after a few days, problem solved. If the condition is ignored, the clutch plates in the differential can be ruined, with the customer facing a hefty repair bill.

Dan Paddy, Paddy’s Auto, Copley, Ohio


If the owner of a Ford F-Super Duty diesel truck complains about intermittent surging and engine shut-off after accelerating from a dead stop, a possible cause is the injector high pressure relay valve.

Even if the valve is good, if the valve mounting is not tightened properly, it can cause the magnet inside to move upon acceleration, signaling the engine to shut off. Make sure the valve is secured properly.

Frank Suffield, Grayling Diesel

The problematic transfer case vacuum actuator is commonly prone to sticking if it’s is not used frequently.
<p>The problematic transfer case vacuum actuator is commonly prone to sticking if it&rsquo;s is not used frequently.</p>


If the owner of a 2006 Toyota 4Runner complains that he or she can’t get it into 4WD, suspect the 4WD actuator. With the 4WD switch engaged, you may have no front-wheel drive and the 4WD indicator light flashes. In all likelihood, the problem is the result of not engaging 4WD on a frequent basis, causing the actuator to stick.

To narrow down the problem, raise the vehicle on a lift. With the engine running, confirm that no front drive occurs when the 4WD switch is engaged (the rear wheels turn but the front wheels don’t). Check front driveshaft movement. With 4WD engaged and the front shaft does not move, this indicates that the transfer case is likely OK.

The actuator is located on the front of the case, behind the front crossmember. Two steel undercovers must be removed to gain access.

If the vehicle has been driven in winter conditions in the past, it’s wise to pre-soak all undercover fasteners with penetrating oil before attempting to remove them.

Also make sure the differential fill and drain plugs will loosen. If stubborn, soak with penetrating oil overnight. These plugs are notorious for being stuck. You don’t want to remove the drain plug and then find out that the fill plug is seized. If the plug is stubborn, repeatedly apply clockwise and counterclockwise torque to help loosen. Each plug features a crush washer. Always plan to install new crush washers. If the plugs were difficult to remove, it’s not a bad idea to replace both plugs with new.

Drain the differential.

The differential must be slightly lowered in order to gain reasonable access, especially to the upper bolts.
<p>The differential must be slightly lowered in order to gain reasonable access, especially to the upper bolts.</p>

Soak the three engine cradle bolts with penetrant. Remove the rear female hex nut from the rear of the cradle and support the differential with a transmission jack. Remove the two front cradle bolts and nuts. Carefully lower the differential as far as possible, in order to provide access to the actuator. Remove the original vacuum actuator. Remove the original packing (sealant) from the case mating surface. Remove the left side bushing mount to allow a bit of further drop of the differential. Lightly coat the new drain plug threads with anti-seize and install the new drain plug and crush washer. Install the new actuator. Use Permatex The Right Stuff gasket maker to seal. Re-install the bushing mount, front and rear cradle fasteners.

Refill the differential with 75W90 synthetic GL-5 lube. This will take 1.5 to 2 quarts. Install a new fill plug and crush washer, with a light coat of anti-seize on the plug threads.

Place in 2WD and start the engine and place the transmission in gear. The warning light should stop flashing. Place it in 4WD and verify that all four wheels move and the light is not flashing.   ●


Wheel nuts require 21 mm socket

Engine undercover bolts require 12 mm socket

Differential drain and fill plugs require     10 mm male hex bit

Right rear differential vertical nut requires 12 mm hex bit

41400-35032 Transfer case vacuum actuator

90341-24014 Plug

90341-18032 Plug

12157-10010 Gasket

90430-24003 Gasket

Willy Baron, West Side Car Care

Post a comment

Comments (1)


Post a Comment

Subscribe Today

Subscribe to Auto Service Professional

Sign up for a FREE subscription to Auto Service Professional magazine