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Yacht Charter Guide

RV Pre-season pre-purchase technical engine analysis

An engine analysis is an advanced system of inspecting our RV’s drive train, oil and cooling system. We perform these tests to help catch pending mechanical issues before we leave our home area saving time and breakdowns down the road.

An engine/drive train analysis is the perfect series of tests to perform if we were considering purchasing a vehicle.

An analysis is much more comprehensive than a typical oil level check and “pre-departure peak” at the engine. We are going to visually inspect our engine, but also take a series of measurements that become our baseline for future tests. Our goal is to use this engine analysis as a system to help make easy informed decisions about our vehicles drive system and make future trouble shooting easier.

One advantage of an engine analysis is repairs can be made while still at home saving time and money.

To begin you should have on-hand as much of the following as possible:
• Camera
• Notepad
• Your collection of electrical meters
• A 0-3 bar pressure gauge (if your engine has a turbo)
• An infer red temperature gauge
• Any other special tools you might have
• A few rags, and spray cleaner

The steps to performing an engine analysis:
1. Visual inspection
2. Pre-start fluid inspection
3. Long hill climb and temperature checks

Visual inspection

This is a general once over of the engine looking for blatant flaws.

Open the engine hood, and look, feel and smell
Look for oil drips or other fluid under the engine. It may help to lay a piece of fresh cardboard under the engine for a few days before this inspection to find new but small leaks.

Inspect for obvious cracked hoses. Give a gentle bend where a hose attaches to the engine and look for cracks in the rubber cover and loose hose clamps. Check the fan belts for cracks. Grab the alternator pulley and be sure you can’t spin it free on the belt.

Feel the inside of the engine compartment for oil film. Touch the areas of the engine you can’t see feeling for rust or water trails. Use a small mirror to help your inspection.

Smell for any burned chemical type odor. Smells can be difficult to locate, but in general any burnt, oily, or diesel or gas smells should be searched out. A good nose can tell the difference between a hot belt and a hot wire.

Look over the complete engine, gearbox and differential for oil leaks. Pay particular attention to the front seal, and the area between the gearbox and engine. Leaks in the front or rear seal can mean a coming engine rebuild. Take a careful look at the head to block connection for oil or coolant trails.

Take photos from all angles as a base line for later use.

This is where many an engine inspection ends, but in an analysis we want better scrutiny to help our confidence in our drive system.

Our next series of checks focus on fluid inspections

Oil

Oil is the lifeblood of our engine. It lubricants, cools and quiets our engine. But how do we know if the oil is doing its job?

Begin by pulling the dipstick. Smell for signs of diesel or gas odor. Pinch a small dab of oil between your index finger and thumb and expand slowly to see how far you can spread the oil before the gap opens. Compare this gap to new oil and take down the difference for your notes. This is a crude method of checking viscosity.

Open the oil fill and look for water droplets, condensation or worse, a gray gooey substance indicating water penetration into the oil.

Put a small drop of oil on a paper towel and compare it to a new oil drop. Note the amount of black carbon and any shiny deposits.

A more careful inspection can include an inside look at the oil filter. Next time you change oil keep the old filter. Leave it to drain upside down then cut open the canister and look at the inside of element. It’s the inside that will contain any heavy deposits or possible metal shavings. Take photos for later comparison.

Coolant

Open the expansion tank cover or the heat exchanger cover where you check the coolant water. The reservoir should be filled almost to the “Full” line with coolant. A low level can mean a small air leak in a hose. Look inside the cap. It should be clean and not have any oily film or brown gunk attached. These are symptoms of a failing head gasket, un-maintained engine.

Diesel or Petrol Filter

Locate your diesel or petrol filters. Most RV’s have two filter sets, one on the engine supplied by the manufacturer and a pre-filter. On the bottom of most any fuel filter will be a drain valve. Drain off a small amount of fuel into a container checking for water, dirt and any long stringy algae. If you find more than a couple teaspoons of water or much dirt then it’s probably time to change the filters. If your filters have a vacuum gauge note the reading for future comparison.

Pull the gear oil dipstick. Check level and perform our viscosity check again. Look for water under the cap or on the dipstick and smell for any burned odor. Most vehicle gearboxes don’t have a filter so any bits of crud or metal keep getting re-circulated so it is imperative we keep an eye on the oil.

Special test with special tools

Were going to runs some test while our engine is working hard to pull us up a long hill. Some the tests are taken with the use of a handheld IR laser gauge. This tool provides a wealth of information and the prices have dropped dramatically over the last few years. They pay for themselves quickly on the first overheating or gearbox problem they solve.

Another set of measurements were going to take are with a gauge called a DC clamp meter. An “amp clamp” as they are often called is a meter with a set of “jaws” that we can place around any wire and measure how many amps are being passed inside the wire. This makes testing alternators and starters simple. We can often see a bad alternator long before they completely fail preventing on the road breakdowns.

Note-If I could only invest in one of these special tools I would purchase the laser temperature gauge for it’s many useful tests.

First start up

Start the engine; wait for oil pressure to build and rev up the engine. Note how the oil pressure built. We want to note the pressure at three different times for our log. Note the pressure at start up, during the hill climb, and lastly just when you release the throttle during our hill climb. Dips, or strange readings can mean a stuck oil pressure relief valve or an engine that is facing a rebuild.

Set your clamp amp to DC and place the jaws around the single positive/red cable at the back of the alternator. Check the output and note the DC reading. Change the meter to AC and again note the reading. The AC reading should be around three amps. If the AC reading is near half of the DC reading this indicates a faulty diode. Faulty alternator diodes cause batteries to fail and random circuit boards to stop working. We make this test early while the alternator is still at full output. We’ll come back at the end of testing and verify the voltage has stabilized around 14.2 volts.

Hill Test

The next series of test is to see how our engine is performing under full load. We want to climb a long hill that will keep our engine working hard for at least ten minutes.
I’m going to describe the next tests as if we are taking them while driving, but if you can’t reach your engine while driving you can still efficiently test. You’ll just have to find a safe place to park at the top of the hill where you can quickly take a series of measurements with our laser temperature gauge.

Preparing to climb

At the bottom of the hill we want the engine to be at operating temperature. We want to “shoot” the engine coolant loop to get a temperature at two specific places. First where the coolant leaves the engine or enters the radiator and second where the coolant leaves the radiator and enters the engine.

This is the in and the out of the engine cooling system. This series of numbers will provide a clear indication of how much heat our engine is producing, and how well the radiator is performing. Driving along on a flat plane at 80K we should see about three to four degrees temperature difference between the in and out. Climbing a hill with the engine working hard we should see no more than ten degrees temp change, and the radiator should be able to pass that amount of heat away from the cooling system. An engine that slowly heats up on this test may mean a clogged radiator, failing head gasket, or other heat related issue.

Take a few more readings around the engine head, and note the oil filter temperature.

Start climbing

Start up the hill and let the engine build some heat. You might see some signs of smoke wafting from the engine. Determine if the smoke is escaping from the engine or if we are simply “gassing” off an old oil/dirt film. Pay particular attention for smoke escaping from between the engine and exhaust manifold. This may be combustion gas that could contain carbon monoxide Carbon monoxide is a dangerous, colorless, odorless gas that can kill when released into confined spaces.

Look behind at the road and note the color and amount of exhaust. Take a photo so you can have a clear comparison for later tests. Black smoke should be expected. This is an engine working hard and not burning all the fuel. Typical for climbing a hill conditions. Blue smoke is oil and may mean the engine is getting a little tired inside. White smoke is from water such as a failing head gasket.

By now the complete engine should be stabilized at temperature and working hard. It’s time to do a few tests with our laser temp gauge.

Can you shoot the gearbox? Look for hot spots. Pay careful attention to the area of the case around the clutch packs, and the gearbox output bearing. If any part of the gearbox is going to build up heat it will be during this hill climb. The complete gearbox should be under 80C, and 60C is typical. If you can’t shoot the gearbox don’t worry, at the top of the hill we’ll get a good reading before it has a chance to fully cool. For automatic transmissions we also want the in and out of the cooler. Again expect about a ten degree temperature change at the cooler.

Continue checking with the laser gauge along the cylinder head. It should show about 75-85C everywhere. There should be no hot spots. A hot spot would be more than a five degree C change in the head from one end to the other.

Check the oil temperature by shooting the oil filter or oil pan. The oil temp should be about 7-10C above the head temperature and not above 95C even when pulling hard.

Check our top and bottom radiator temperatures again. With most engines the temperature difference should be less than 10C. A higher temperature difference can indicate an engine producing too much heat (IE failing head gasket) or too little water flow (IE clogged radiator).

You should be able to move the laser along the tubes of the radiator and show each tubes cooling effect. With careful inspection any blocked tubes can be identified. Check how far from the top of the radiator the temperature continues to drop. By this method you can see how much reserve cooling you have left in the radiator and make an informed decision when to make repairs.

The pre turbo exhaust temperature should be about 300-450C. After turbo it should be 50-100C lower. Check the exhaust gas temp between the cylinders and exhaust manifold for each cylinder. Normal for a loaded non-turbo engine should be 300C-350C. A cylinder temp lower than the rest shows a clogged injector, bad spark plug or maybe a dead cylinder. A high cylinder temp possibly shows a leaking exhaust valve, or poor injector spray pattern.

Locate the crankcase ventilation hose and feel the outlet for crankcase pressure. If your engine does not have an easily accessible vent line you can also check for crankcase pressure at the oil fill. Slowly open the oil fill and check for “blow by.”

Blow by is the amount of gas and oil mist that seeps by the piston rings and pressurizes the crankcase. Excessive blow by can mean worn out rings. You should not feel any pressure in the oil fill. Crankcase pressure should not be above a pound of pressure.

Note-Be careful opening the oil fill, this may release little hot oil droplets being thrown off the rocker arms.

If the engine has a turbo, find a port on the intake manifold and check the pressure. Compare this to the manual. Many turbo chargers boost up to 2 bars. The pressure should be stable. Any cycling of pressure, or “coughing” can indicate after burning, blow-by, or clogged air inlet.

Slow down and park

Take one last look for any signs of future problems and slow the engine down to an idle and park, but leave the engine running. Check with the laser temp to see if the engine cools quickly (less than 5 minutes).

Check the gearbox and differential temperature. Expect 60C from a working gearbox and more after a long hill climb. Use this number as your baseline to keep an active account of how your gearbox and differential are performing.

Take the temperature of very universal joint. Long before they begin to “clunk” they will show signs of heat. A hot universal joint should be inspected and or changed.

Verify the alternator is producing 14.2 volts. Less means the voltage regulator needs to be inspected, and more may mean we are cooking the batteries causing early failure.

Shut the engine down.

Load test the starter

Place the jaws of the clamp amp over the positive cable leading to the starter. Clip your voltmeter to the starter’s positive and negative. Hold the STOP button, or engine shutdown and turn the engine over for ten seconds. (The engine should not start.) Note the amp draw. On a typical engine the reading should be 225-275 amps. Look at the starter for a rated amperage or wattage. (Watts/volts=Predicted amps. They should match) anything more indicates poor cables, a bad armature in the starter, or failing batteries. The voltage during this test should remain above 9.5 volts. Less means inspect the cables or battery. The results of this test should be recorded for future reference.

Note-During the starter load test carefully listen to the way the engine turns over. Each cylinder should sound the same. A “miss” or different sounding cylinder “hit” may mean a cylinder with low compression.

Pull the air filter and inspect for cleanliness. Reach a finger down the air inlet. It could be lightly covered in dirty oil. A little oil film is normal, but any loose oil or splatter indicates a possible faulty inlet valve, or maybe a turbo failing.

If the engine has a turbo charger you might be able to reach inside and give the blades a spin. They should move easily with no restrictions, or any “bumps”.

Conclusion

For most drivers an in-depth inspection of the RV’s drive system can mean more confidence, safer travel and a much easier time of finding trouble spots in the future.

Remember to keep careful records of all the tests performed so in the future when something has changed we can repeat the tests making short work of the trouble shooting and quickly get back to enjoying the road.

Call now to book a charter with Captain Scott Fratcher