Tech Stuff

Tips From Techs

We learn something new every day. The sharing of experiences and diagnostic knowledge among technicians improves the automotive service industry as a whole.
<p>We learn something new every day. The sharing of experiences and diagnostic knowledge among technicians improves the automotive service industry as a whole.</p>

Our 6th annual advice column written by technicians working on the front lines.

NO BRAKE LIGHTS?

A 1995 Chevy G20 van recently came into the shop with an issue of no brake lights. After checking the normal areas such as wiring, fuse, bulbs, etc., we suspected the brake light switch which is mounted to the power booster rod where it connects to the brake pedal arm. Still nothing.

We did notice that by manually operating the switch, we had brake lights.

To make a long story short, the owner had recently replaced the brake power booster, but the local parts store had sold him the incorrect unit (probably not their fault, but likely the fault of the reman shop that rebuilt and mis-packaged the booster).

Mystery solved: The perplexing no-brake-light issue was caused by the power brake booster’s rod, after a previous shop had replaced the booster.
<p>Mystery solved: The perplexing no-brake-light issue was caused by the power brake booster&rsquo;s rod, after a previous shop had replaced the booster.</p>

As it turns out, the 1994-1995 Chevy van requires a very specific rod in the booster with about a 1/4-inch longer chamfer cutout than the one the owner had purchased, necessary for proper activation of the switch.

Upon discovering this, we obtained the correct booster (we made sure that the rod was correct) and presto — the brake lights worked.

Had we not accidentally found out that the owner had replaced the booster, we probably never would have thought about examining that booster rod and would have wasted even more time tearing our hair out trying to diagnose the problem.

Rob Holland

Bobby Y Garage

MYSTERY BRAKE FLUID LEAK

Have a vehicle with a “mystery” brake fluid leak? It might be a very small leak that eventually runs the master cylinder reservoirs low.

If a brake fluid pressure switch is found on a distribution block/proportioning valve, disconnect the connector and inspect the top of the switch. Fluid might be leaking actually through the switch.

A small fluid leak that can be difficult to spot may be caused by fluid passing through a brake pressure switch, into the terminal contact pocket.
<p>A small fluid leak that can be difficult to spot may be caused by fluid passing through a brake pressure switch, into the terminal contact pocket.</p>

If so, the sliding valve inside the distribution block had worn or faulty seals, allowing brake fluid to enter the port at the switch. The distribution block must either be rebuilt or replaced. Simply replacing the switch won’t fix the issue.

Mike Laslow

Chippy’s Garage

HONDA INTERMITTENT STALL

Have a Honda that stalls out on a random basis? Rather than automatically assuming that the fuel pump might be bad, check the ignition switch.

With the engine idling, simply wiggle the ignition key (don’t turn it... just wiggle it). If the engine suddenly dies, the problem is the ignition switch.

We see quite a few of these.

Jeff Lance

Harper Brothers Service

SCREECHING POWERSTROKE STARTER

The owner of a 2002 Ford F-Super Duty equipped with the 7.3L turbo diesel engine complained about a buzzing/screeching starter noise during intermittent engine start attempts.

Assuming he needed a new starter, he brought the truck to our shop for a replacement. Since we were already aware of the propensity for these diesel starter’s mounting bolts to loosen over time, we first checked bolt tightness. Sure enough, both bolts (this was a two-bolt starter) were extremely loose, allowing the starter to jump around with intermittent engagement of the bendix.

Luckily we caught this in time, avoiding damage to the flexplate teeth. The original “factory” specification for the 10 mm x 1.5 bolts calls for 16-20 ft.-lbs. (Haynes manual lists 18 ft.-lbs.), but some replacement starter instructions call for as much as 40-57 ft.-lbs. We opted to tighten both bolts to 38 ft.-lbs. After tightening the problem was solved. The owner was delighted to avoid spending around $250 for a new starter and labor. Since he was a good and loyal customer, we didn’t charge for the bolt tightening.

Doing that favor for him didn’t hurt our bottom line and increased his loyalty to our shop, resulting in him sending numerous friends and relatives to our shop as “the place to go.” Whenever a Ford diesel truck is on the rack, take a moment to check starter bolt tightness. Even after being torqued to spec, they sometimes have a nasty habit of loosening over time.

Larry Ritz

Smitty’s Car Care

HARD HONDA SHIFT

If you encounter a 2006-2010 Honda Civic with hard or delayed shifts with an automatic transmission, a stuck-on 3rd clutch pressure switch could be the cause. You might see DTCs P0756 (shift solenoid valve B stuck off) and/or P0847 (short in transmission fluid pressure switch B circuit or fluid pressure switch B/3rd clutch stuck on).

Check the onboard snapshot and look at the 3rd pressure switch value in the data list. If it reads ON (closed) at idle or a stop, drain the ATF through a strainer and check for debris. If the fluid is clean, replace the switch. If the fluid has debris, it’s time to rebuild or replace the transmission.

Gary Swinton

Clay’s Service

DIESEL COOLANT CONCERN

Far too many owners of diesel-powered trucks tend to ignore the engine’s coolant condition. The extreme pressures during the combustion cycle can cause cavitation where air bubbles can enter the cooling system between the block and cylinder liners, creating pinholes in the liners. This can also reduce the level of nitrite, which is designed to protect the liners.

Engine coolant condition is vital in any engine, but in a high-compression diesel engine, it’s even more critical. Use of a refractomer allows you to quickly monitor coolant condition.
<p>Engine coolant condition is vital in any engine, but in a high-compression diesel engine, it&rsquo;s even more critical. Use of a refractomer allows you to quickly monitor coolant condition.</p>

Changing coolant on a regular basis, around every 30,000 miles or so, can protect the cooling system and maintain the nitrite level. Check your customers’ engines coolant condition using a refractometer or hydrometer whenever the vehicle is in the shop.

Rick Crom

Diesel Specialists

NO-BOOST CAUSED BY CAT CONVERTER

We recently had a 2004 Ford E-Series 6.0L diesel van ambulance that was very intermittently losing turbo boost even after turbo replacement. The vehicle set a P2262 code before turbo replacement.

We inspected and cleaned the turbo the first time, replacing the unison ring. We returned the vehicle to the customer after our normal test drive, as we thought the problem was repaired. The customer brought it back with the same issues. That time, P2262 was again set and we verified what appeared to be turbo vane sticking problems.

We decided to replace the turbo, road tested and it appeared to be OK. We returned it to the customer. The customer said that on the way home it acted up again.

The van came back and we road tested for 1 to 1.5 hours. At about 1 hour of driving, with light on throttle and slowing down, I looked at IDS pids and VGT operation number was 20%. When I accelerated, the percentage only went to around 40%, with only building 5 psi boost under hard acceleration.

After feathering the throttle I was able to get about 10+ more psi. After getting through that test run, the vehicle was parked for a few hours and then headed out for another test drive. Not long into that test drive, we had low power and low boost again, with codes P2262 and P2263 set.

I wondered why the vane closer percentage was so low without boost. I would think that I would see that type of problem if over-boost was occurring. My thought was that low of a percentage may have the VGT mechanical components at the far end of travel, causing binding and difficulty recovering once calling for power. But I wondered what would cause the PCM to request that.

We did have one van here recently that had the CAC hose hot side at the CAC end so spongy that it would suck shut, causing low boost. We checked that and this van doesn’t appear to have that problem. I did think about the throttle plate possibly sticking or interfering with air flow.

A friend, Nick Sharp at Diesel USA, suggested checking the catalytic converter, as he recently had two come apart, causing exhaust to be blocked, causing a no-boost condition. I have seen converter issues but generally they were consistent and not intermittent. Apparently the converter was loose internally, rocking from good flow to poor flow, causing the intermittent power and boost loss. After replacing the converter, we did another 3-hour round trip we returned the van to the customer and it’s been fine since. Another lesson learned.

Matthew Musser

Diesel Systems Sales and Service

LS BALANCER

Crankshaft balancers on GM LS engines feature only an interference fit to the crank snout, with no locating key. The fit is very tight, and the balancer bolt torque procedure involves several steps.

General Motors’ LS engine series features a non-keyed crank pulley that requires a fairly serious interference fit. Don’t be tempted to hone out the center hole to ease installation or with future removal in mind.
<p>General Motors&rsquo; LS engine series features a non-keyed crank pulley that requires a fairly serious interference fit. Don&rsquo;t be tempted to hone out the center hole to ease installation or with future removal in mind.</p>

First, install the balancer using an old (original) bolt in order to fully seat the balancer. Torque that bolt to 240 ft.-lbs. Then remove that bolt and install a new bolt (these are torque-to-yield bolts and cannot be re-used). Next, torque the new bolt to 37 ft.-lbs. Finally, rotate the bolt head an additional 140 degrees. It’s also advisable (but not mandatory) to replace the balancer with a new one in order to ensure a good interference fit.

NOTE: Because of sometimes difficult removal, someone may be tempted to hone the center bore of the balancer prior to installation to make installation and future removal easier. Don’t do it. If the balancer does not have enough of an interference fit, when it gets hot, the hole can expand, causing the balancer to start to spin on the crank snout, which can in turn cause the bolt to begin to loosen. This can result in the balancer starting to walk off, causing a front seal oil leak or worse.   ●

Bob Fall

Fall Automotive

Tags: Mike Mavrigian 
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