Undercar: Diagnosing And Repairing Wheel Bearing Noise
Adapted from Bob Dowie’s article in ImportCar
Dissecting the Popular Honda B-Series
Over the last decade, the engines that have been used in the Honda and Acura line of cars and SUVs not only deliver many miles of service, but their performance level sets a standard that few car makers in their class have been able to match. Additional proof of both the reliability and potential of these engines is the popularity they enjoy in the sport compact market. I think its safe to say that the popular B-Series twin-cam Honda engine is the current-day small- block Chevy, enjoying great popularity among both tuners and vehicle owners in general.
Presenting a Diagnosis
Thats not to say theres never been a problem with these engines, but theyve certainly been few and far between. One such problem is head gasket failure on early 90s Civics. Honda was quick to react to the problem and developed a gasket and hardware to remedy it. A TSB lists the updated gasket and head bolts that will prevent a recurring problem. (See sidebar)
We wont cover the nuts and bolts of head gasket replacement in this article, since your technical information system will walk you through those procedures. Instead, well talk about head gasket failure symptoms and diagnostic strategies. As you become a master technician, you will find that its the slightest head gasket leaks that will present the biggest diagnostic challenges. In such cases, the customer usually will notice a symptom that results from lost coolant. It may be an overheating issue but, many times, its a problem the customer doesnt relate to low coolant. It might be a no heat or the heat is coming and going complaint, or the idle fluctuates as a result of the low coolant level not allowing good flow to the warm-up device. When you ask your customer if he/she has noticed a coolant leak, the answer will be no.
The more severe cases of head gasket failure will be easier for the customer to notice. Its hard to miss the telltale white steam coming from the tailpipe in the morning and the accompanying odor of coolant burning. If they ignore it for just a couple of days, the overheating will bring them to your shop soon enough but, hopefully, not on a flatbed. There is always the threat of the engine hydrolocking as a result of the cylinder being filled with coolant, preventing it from cranking over. When faced with this situation, dont continue trying to start the car. Pull the plugs, cover the holes with a shop towel and crank the engine. Theres no missing the coolant escaping the cylinder.
With less obvious coolant loss (even though the customer noticed no leaks), our first step is to check for external leaks. Put the pressure tester on the car and check the usual suspects, like the radiator. Look at the bottom of the timing cover for evidence of a water pump leak, take a good look at the thermostat housing area and move the hoses around. Be patient; sometimes there will be only a slight leak, so give it time to surface.
While external head gasket leaks arent common on Hondas, they can occur and should be no problem to diagnose. Most will leave evidence and can be confirmed with the pressure test. But make sure that the leak isnt originating elsewhere. You dont want to replace a good head gasket if the leak is actually the thermostat housing disguising itself, with the coolant traveling down the head-to-the-block seam. Also be aware of the oil-to-coolant oil coolers used on some models. This sandwich-plate device mounted between the filter and the block has coolant running through it to maintain a stable oil temperature based on coolant temperature. As these vehicles get older, weve seen the effects of road salt and rust end up as pin holes in these units, easily mistaken for a coolant leak at the head gasket.
If no external leak turns up, check for an internal one. There are a couple of ways to proceed two tests that are each performed with the engine running. One is a dye test where the air thats at the top of radiator tank is drawn into a turkey baster-type device fitted with a check valve, and then passes through a dye that changes color if exhaust gases are present. This is a reliable test as long as the chemicals are fresh (the dye has a relatively short shelf life). A variation to this test is to use your exhaust analyzer to sniff the same air that the dye is analyzing.
When performing these tests, take caution to avoid coolant contamination. If contamination mistakenly happens with the dye, it will cost you some chemicals. But, needless to say, the consequences are much greater if you suck coolant into the exhaust analyzer.
The most accurate and our preferred test method is a cylinder leak-down test. This test involves bringing the cylinder to be tested to TDC and introducing compressed air into the cylinder, while observing the coolant level in the radiator. A leak-down tester lets you see how much the cylinder is leaking in percentage points. We use a dual gauge tester where you set the regulator for 100 psi going into the cylinder, while the second gauge will show what the cylinder will hold. This is very useful information to determine how well the valves and rings can control the cylinder pressure. Always make note of the readings as they give you great insight into the engine (more on this later).
Now, lets go back to the head gasket test. If, after a couple of minutes, there is no reaction in the radiator, remove the pressure, turn the engine counterclockwise until the next cylinder in the firing order is at TDC and do it again. Follow the firing order and test all of the cylinders.
The final gasket failure to consider is compression leakage between cylinders. This failure, and the resulting poor-run condition, is hard for a customer to miss. And, if its overlooked for any length of time, it will result in a very expensive repair. The aluminum cylinder head has little tolerance for those hot gases and extreme pressures passing over the mating surface, and it doesnt take long for the casting to be damaged, resulting in the need for a rebuilt head to be installed.
In severe cases, the block will also be damaged. This failure will be evident with a compression test and will certainly be evident during a leak-down test. Be sure to remove all of the spark plugs before the compression test. This type of failure is rare on Hondas, and is often the result of the extreme cylinder pressures caused by detonation. Dont return the car without determining the cause. While its a good practice on all cylinder head service, be certain that the EGR ports are clear and the system functions as designed. Check exhaust backpressure, making sure a restriction there isnt increasing cylinder temperature.
Testing Without the Heads
Damaged valves are another problem that will require you to remove the cylinder head. Whether the valves are burnt or bent, these problems will result in a misfire condition that wont take long to confirm. Both can be quickly identified with a compression test. Checking the valve lash will further confirm the condition.
As a rule of thumb, a burnt valve will have tight lash while the bent valve will be wide. Keep in mind that bent valves are the result of timing belt failure. If you find an engine that has bent valve symptoms, and no recent belt failure is reported or evident, consider carbon buildup on the valves and stems as a cause for the wide lash and lack of compression.
There have been cases reported where the combination of low compression and the absorbent nature of the carbon will cause a no start condition that disguises itself as a bad timing belt. If youre checking the valve lash, you already know the belt didnt break. In some cases, you can get the valve to seat by pushing the valve open and letting it snap shut.
Another strategy is to put top-end cleaner into the manifold and let the car sit overnight so the chemical can soften the carbon. Be sure to crank the engine in the morning without the spark plugs installed to prevent hydrolocking the engine and the resulting damage. Whatever method you use, when you get the car running, a good top-end cleaning is certainly in order.
Once a problem is confirmed and the head comes off, there are a couple of other tests to perform and decisions to be made before the head is reinstalled.
Whenever a head is removed, spend a few minutes with a flashlight looking closely at the head and ports. Carbon buildup should be easy to detect. Inspect the valves for any signs of overheating at the edges of the valve face. Look at the valves and seats that are being held open by the cam. Badly pitted, poorly seating valves should be serviced. If you did a leak-down test, pay particular attention to any cylinders that showed high leakage. Check the head for flatness using a straightedge. More than 0.003-in. of warpage should trigger a head resurface, while heads that have experienced extreme heat and the damage that comes with it may require replacement with a rebuilt unit to ensure a quality repair.
Reattaching the Heads
Your service information will provide the nuts and bolts of reassembly procedures, but there are a couple things to keep in mind. When cleaning the gasket surfaces, its tempting to grab the offset die grinder and use surface refinishing discs. I suggest resisting the temptation. While sanding off the gasket may save some time, the resulting dust and material removal could compromise an otherwise first-class job.
Theres no reason this open engine doesnt deserve the same treatment that you would give an engine you were rebuilding on a stand. The discs can also remove enough material from the edges of the gasket surfaces that sealing could be compromised. That doesnt mean that traditional gasket removal doesnt require care to avoid damaging parts or keeping debris out of the engine. Its just less likely to be a problem.
When the surfaces are clean, be sure to check that the oil passage that brings oil to the camshaft and valvetrain is free of debris and clear on both the block and head. I would say the only time youll get away with a simple gasket replacement is when youre dealing with a lower-mileage car that hasnt had the updated gasket installed. If the gasket failure is the result of an overheating situation, youll find the head is warped as a result of the heat. If it got really hot, its a safe bet that the valve seals felt it and should be replaced. At that point, a valve job seems like the way to go. Of course, its most important that the cause of the overheating is identified and repaired. Hopefully you included a timing belt, water pump and thermostat in your estimate that will cover you there, but be sure to check the radiator and hose condition before you finish the estimate. Check the condition of the radiator cooling fins. On some models, you can get an idea of the internal condition by simply removing the cap, while others wont afford that option.
Consumption and Smoking
This brings us to the great ring debate. Hondas seem to have a problem with excessive oil consumption and the smoking that comes with it after a valve job has been performed. There are a couple of theories to support why this happens, but there is no disagreement that it does take place. Its our policy to replace the piston rings whenever a valve job is performed. The good news is on the four-cylinder cars, this doesnt make the job so expensive that it becomes out of the question for even an older car thats in good shape. Certain models have had problems with oil consumption without the heads being removed.
The most common is the early- to mid-90s Prelude. While some techs have blamed and replaced valve seals to solve this problem, its usually piston ring replacement that will fix the car. I mentioned earlier that a leak-down test is a good way to check the integrity of the compression rings and valves, but thats not the case for the oil rings. As far as I know, there is no test for the oil rings. I suspect the rings over the valve seals if the smoking persists longer than it would take to clear out the cylinders after start up. Id still do a leak-down test on the engine before disassembly to check the sealing capabilities.
When replacing rings with the engine in the car, honing is not required or recommended. It comes down to the same issue as with gasket removal the threat presented by the grinding dust outweighs any benefit that honing offers. If the cylinders are damaged, the engine will need to be replaced or a full rebuild with a bore job and oversized pistons is in order.
Other than the problems already mentioned, most engine problems youll see on Hondas will be the result of poor maintenance practices. Whether its a bent valve, burnt valve or a blown head gasket, its a safe bet that it could have been avoided with proper maintenance.
I still believe that valve adjustment should be part of a 60,000-mile service. Honda has changed the valve adjustment interval on its cars to include the wording audible inspection only; adjust only if noisy. The problem is that we are more concerned about a tight, rather than loose, valve. This is critical on the popular CR-V model where the specs are a tight 0.003-0.006-in. for the intake and 0.006-0.007-in. on the exhaust side. There is little room to compensate for wear before the valve is being held off the seat, resulting in a misfire or, if ignored, a burnt valve.
If youre faced with a poor run when cold condition or a mysterious misfire code, suspect a tight valve. You may be wondering why it would present itself as a cold-run problem. Its the result of the aluminum head expanding at a greater rate than the steel valve. As the engine heats up, the head will grow, moving the rocker away from the valve stem. This will result in valve lash and sealing of the cylinder. Its further proof of why its important to adjust the valves with the engine temperature as specified by the manufacturer. Thankfully, Honda uses a cold setting, which makes the job much easier.
In addition to allowing the cylinder to seal, valve lash is important to allow the valve to transfer heat to the cylinder head. Without the opportunity to spend some time on the seat, it doesnt take long for the 1,400 F exhaust gases passing by to burn the valve and damage the seat, resulting in an expensive valve job. While regular valve adjustment is critical on the CR-V, its a good practice on all of the four-cylinder Hondas. While the larger specs are more forgiving than the CR-V, they will tend to tighten up. This is most important on cars that are driven hard, and a good practice on all models.
Were well aware that regular cooling system maintenance will prevent overheating problems and the radiator blockage that leads to head gasket failure. Its important that in the future you educate customers on the value of cooling system maintenance. We all should be recommending water pump and drive belt replacement with a timing belt job, but consider adding a thermostat to the list. Its a good time to replace it while the system is empty, it doesnt add much to the price and, when youre done, you and the customer can be confident that the cooling system is in good shape.
I hope you feel more confident that youre ready to diagnose and tackle top-end sealing services on four-cylinder Honda and Acura engines, and will be able to educate your customers on the benefits of preventive maintenance that will safeguard their vehicle from needing these repairs in the first place.
Remember: An ounce of prevention equals a pound of cure.
When testing for head gasket leakage, were concerned with the reaction of the coolant in the radiator to the pressure. When the offending cylinder is pressurized, its hard to miss the reaction of the coolant. Ill give what looks like good cylinders a couple of minutes just to be sure. If you find high leakage, it takes only a couple of minutes to determine whats leaking. Using a stethoscope, listen for escaping air in the spark plug holes and dipstick tube, checking how well the valves and compression rings are sealing. While you can check the valves by listening in the intake manifold and exhaust pipe, Ive found that its easier to hear the air that escapes from the tested cylinder into the manifolds and finds its way into the cylinder that has the valves open.
|Q: Have you heard of any solutions for coolant loss and an oil leak on a 1.6L Honda Civic?
A: The AERA Technical Committee offers the following information regarding a cylinder head gasket leak on 1988-’95 1.6L Honda Civic engines. (Note: This information does not apply to the VTEC engines.) You may have received complaints that oil is leaking externally or there is coolant loss.
This information also supersedes Honda service bulletin 97-047, dated September 29, 1997. The current corrective action prescribed by Honda involves installing a new style (MLS) cylinder head gasket and the new head bolts, p/n 90005-PM3-004 (10 required). It is important to note that the following torque procedure should only be used for the new revised style head gasket, p/n 12251-P01-004.
Use the procedure listed below to install the revised MLS gasket for 1988-’95 1.6L non-VTEC engines.
Carefully remove all gasket material from the head and the block with gasket solvent and an adequate scraper. The head and block mating surfaces must be clean, flat and smooth for the new head gasket to seal properly. Note: Do not use power tools or abrasives to remove the gasket material, as they will damage the head and block surfaces causing the new head gasket to leak.
Before the gasket solvent dries, rinse any pieces of the gasket from the coolant passages in the head and block with water. You must remove all of the gasket material to prevent engine overheating.
Position a new head gasket on the block and install the cylinder head. Do not use any gasket sealers (Honda gasket) on the gasket or mating surfaces.
Apply engine oil to the threads and washers of the new cylinder bolts. Install the bolts, and torque them in the sequence and steps shown (see Figure 1). Do not use the head bolt tightening steps in the service manuals.
Follow the next four steps.