Wednesday, November 23, 2005 was our 2005 edition of the Club's winter technical session. The people at Volvo of North Vancouver graciously opened up their shop bay doors to host an informative and entertaining evening. Master technician Ian Peterkin took the enthusiastic audience through the timing belt replacement on a 1980 Volvo GT with a B21F engine.
This article covers the timing belt replacement of Volvo single-overhead cam (SOHC) engines. We will cover the procedures, tools and supplies needed, and some of the typical snags you might face in this task.
Ian's presentation began with the reasoning behind automobile manufacturers' decision in switching from timing chains to belts. Although there have been many arguments as to why manufacturer's switched from using timing chains to belts, including weight, noise, reliability, cost and so on, the decision came down basically to cost. Volvo's B21 overhead cam engine was their first instance of using a timing belt, hitting the market in 1975. It is interesting that some car manufacturers have recently been advertising the use of timing chains on their engines.
For the B21, the scheduled replacement interval is 80000 km. This figure was probably chosen as a tradeoff between belt reliability and the increased cost of frequent belt replacements. The number of kilometres that a belt will last before breaking varies greatly. The distribution shows the statistical liklihood of breakage at a given point. The majority of belts will last longer than the recommended change interval, however, the odd rogue belt may break prior to this limit. Following the manufacturer's recommended replacement interval will minimize the occurrence of belt failure.
The Volvo SOHC engines are non-interference engines meaning that pistons and valves will not collide with one another in the event of a timing belt failure. It essentially means that you have to replace the belt – once you have your car towed home. In contrast, the B234 double overhead cam (DOHC) engines are interference engines. A broken timing belt will result in the engine being badly damaged. Pistons and valves cannot occupy the same space at the same time.
Belt replacement is normally straightforward. However, some tricky situations may arise making progress difficult and so it is wise to plan the work in advance. For example, crankshaft damper nut, the damper itself, miscellaneous other hardware. This article will provide solutions to some of these predicaments, something that the automotive manuals normally do not include.
This process essentially covers all SOHC engines, 1975 to 1995, with minor differences when it comes to ancillary components such as guards, shrouds and belt-driven accessories.
The first step in safety is to disconnect the negative terminal of the battery so that the engine cannot accidentally be turned over while working, the outcome of which could lead to very serious personal injury.
First off, remove the nuts securing the fan to the water pump. It was at this point that we met our first hurdle. These nuts were in no hurry to move. Ian pointed out that the situation is often difficult and that it is particularly easy to damage the nuts. A common ring spanner cannot be used here because of the fairly narrow clearance between the ends of the studs and the fan clutch. I overheard Glenn Little saying that he has fashioned a low-profile box-end wrench by grinding it down to the right thickness to allow for easy access. Of course, the other part of this task is holding the pump shaft from turning while applying the torque on the nuts. This can be easily accomplished with the use of an over sized screwdriver holding the clutch.
After an extended period of tenacity on behalf of these nuts (many of the observers had broken off into their own small study groups) it was time to bring out the serious equipment. Ian disappeared into the back storage room and reappeared with an oxy-acetylene kit. Heat was the never-fail solution. Now not everyone has welding equipment at their immediate disposal, so one may have to make due with a butane, propane or MAP gas tiger torch. It is important to use some caution and not light the car on fire, melt or burn anything in the process. Ian used a large-gauged metal plate to protect the back side of the fan clutch assembly. After this judicious application of heat, the nuts finally yielded and came loose. As we will mention again later, always replace these nuts with new, shouldered nuts. Once apart, the fan and shroud were able to be removed and set aside. This really opens up the front part of the engine. I was saying to someone else there that the first thing I would have done was remove the shroud. But, of course, it won't come out in one piece with the fan still on, so the work on the fan nuts can be complicated by this fact.
Remove accessory drive belts and put them aside.
On the topic of planning ahead, this would be a good time to consider how you will remove the nuts holding the timing wheels in place. If you do not have access to either counterholds or impact wrench, you may consider cracking loose the bolts on both camshaft and intermediate shafts.
You need to have a means of getting the crankshaft damper nut off and then back on. The factory sells the recommended crankshaft counterhold, which does a great job. If your car is equipped with a manual gearbox, simply select top gear and make certain that the hand brake is securely set. Holding the engine is more difficult if you have an automatic transmission. There is apparently an inspection cover that can be removed on the housing. A pry bar can be used to stop rotation. Others suggested removing a spark plug and inserting a length of nylon rope into the cylinder and then turning the engine until that piston impinges the rope.
If you have an impact wrench, the job can be made substantially simpler. However, there is always concern about using an impact wrench on the crankshaft for fear of damage. The jury is still out on this, but no one was able to present any evidence of damage. On tightening, it is not possible to follow the factory specification on torque using an impact wrench. We were, however, warned against using an impact wrench on the 850.
Getting the nut off does not necessarily mean that you are home-free. It is possible that the damper may be rusted firmly onto the crankshaft making it extremely difficult to pull off. I faced this on our B230FT the first time that I replaced the belt. In the end, it was necessary to call in someone who actually knew what they he was doing. The trick is to use a set of pry bars, placing the tip behind the inner part of the damper and, using a rocking motion, try to ease the damper off. Do not pry on the outer part of the damper as you are most certain to ruin the rubber insert of the damper. One of the pry bars can be wedged against the end of the intermediate shaft which is, of course, still inside the plastic cover. Once the damper is off you will want to completely clean the interface and apply grease before reassembly, thus making subsequent removals much simpler.
On the B230, you should be aware that the damper is put together with rubber sandwiched between the inner and outer metal parts. There have been cases where the outer spins relative to the inner. This will be evident when trying to time the engine. You may notice the timing marks on the outer being far from correct. These dampers are quite costly at about $300.
This particular engine had shims on the crank pulley. These should be put aside in a safe place so that they are not lost, damaged or forgotten about.
This is an excellent time to evaluate the state of the water pump. If the pump is pushing 200,000 km, it should be an easy decision. Just replace it. If it is a fair bit newer you will want to have a good inspection to see if there are any signs of coolant seepage. This can best be done with a suitable light and mirror to have a good look in the drain hole on the under side of the casting. See photo. There have been cases where coolant has leaked out of the thermostat housing and run down to the block interface and then followed that around to the water pump, making the leak appear there. Given the easy access available with everything else off, it would be an opportune time for water pump replacement. Mitigating the effects of corrosion can be as easy as replacing your antifreeze every two years. Ian strongly recommends not going cheap with the antifreeze. It's just not worth it.
The next step in the procedure is to remove the plastic timing cover. It is important to note that the bolts holding this on are not overly large, something like M-6 and M-8. As it is only a light plastic cover, the bolts do not need to be extremely tight when replacing the cover. Over-tightening the M-6 bolts in the head will almost certainly result in damaged threads in the aluminium head.
You should strongly consider replacing all the shaft seals while everything is apart. Significant accumulation of oil in the timing belt area is suggestive of oil seal leakage. You should also check the condition of the crankcase ventilation system as a plugged ventilation system will cause a build-up of pressure and force oil out through the seals. More information can be found in a previous technical article.
Next, line up all of the timing marks. Pop the distributor cap, allowing for inspection of the rotor angle. Now would be a good time to have a look at the photos of the timing mark on each of the three shafts, mainly to become familiar with them. Once the cap is off, care should be taken when rotating the intermediate shaft. The rotor may catch the rotor cap clips and bend or break them. It may be helpful to use a paint marker to highlight the marks. Once the camshaft timing marks are aligned, the other two follow by default. The belt is removed by first loosening the nuts securing the tensioner and then pushing the tensioner against its spring using a suitable pry bar. This method is preferred to pulling on the long span of belt between the cam and intermediate shafts as this will cause the shafts to depart from their marks. In reality, there will be many great opportunities to have the shafts spin, so don't worry too much about this. Once the tensioner has been compressed, it can be held in place by inserting a 3 mm diameter wire or drill into the hole. This will hold the spring compressed and allow for the removal of both belt and tensioner.
It would be wise to have a good look at the belt tensioner and replace it if necessary. I recall a case of a VW Rabbit engine (using a very similar system) whose tensioner seized. The result, of course, was the rapid destruction of the timing belt. The tensioner is essentially a fancy flat roller wheel supported on bearings. You will want to watch for excessive noise (this one was pretty good), adverse slop or abnormally high drag. By this age, the tensioner will spin freely with little drag. A new one, on the other hand, feels like a new one. Quiet, smooth, no wobble, but slightly stiff to spin. The cost will run well over $100, so they are not exactly cheap.
With the belt off, the next phase is to undo the timing wheels on the three shafts. The shop manuals may suggest using counterholds for this job. I have a counterhold for a B230, but B21- B23 engines have a different damper assembly and will not accept this counterhold. One method that I have used with success is feeding the old belt through the bracket on the PulseAir bracket, if so equipped, and around the camshaft wheel. Pull the belt tight.
Once the timing wheels are off, you should clean the front end of the engine to make certain that it is scrupulously clean. This will lessen the risk of introducing dirt into the engine. Ian used a type of brake cleaning solvent. There are a number of cleaners that one could use, but Ian warned us against getting anything on the water pump seals. I mentioned that I have had good luck with a product called PreSolve, manufactured by LPS Labs. You can also find a variety of cleaners and degreasers at your local automotive parts suppliers.
Now that the front of the engine is clean and dry the shaft seals can be taken out if you have chosen to replace them. They are fairly inexpensive and so it is wise to change them at this time. The seals can be prised out with a small lever, taking extra care not to nick or damage the shaft seal surface. Clean and polish the shaft seal surface with 600 abrasive cloth or paper using a rotary motion. Clean the shaft thoroughly. If there is a noticeable groove where the old seal has been running, then you should strive to install the new seal to a different depth so that is runs on a fresh, clean surface.
The new seals can be pressed into place using a variety of different tools. It is necessary to first lubricate the seal surface prior to pressing it into place so that it will not be damaged either during install or when the engine is first started. Historically, people have used grease for this purpose, however we were warned against this as the belief now is that the grease will stay on the seal and eventually ruin it. Instead, Ian recommends using either petroleum jelly (Vaseline®) or simply engine oil as they will not harm.
Next, replace the timing wheels and snug up the retainer bolts. You may wish to defer torquing these until the belt has been installed.
You will notice a series of white lines on the new timing belt. These are proving marks that act as a double-check to ensure that the timing is correct on all shafts. It is completely evident by their spacing which line goes on which wheel. Install the belt and tensioner and then using the belt to compress the tensioner, remove the 3 mm tool to release the tensioner spring. Tighten the tensioner nut. You should double check that all marks line up both with the belt lines and the engine marks. The crankshaft mark will only come in contact with the belt line once the engine has been turned over part of a turn. Give the belt a tug close to the tensioner then loosen the tensioner and re-tighten to factory specification. Torque the timing wheels to the correct value. Rotating the engine should prove that the marks on the belt line up with the marks on the crankshaft. You will want to give the engine a couple of rotations by hand.
Finally, replace the plastic timing cover, crankshaft damper, accessory drive belts, fan and shroud using new shoulder nuts. Replace the distributor cap if it was off. Go over the work one more time to ensure that all everything is good and that there are no tools left inside the patient. Reconnect the battery and fire up the engine.
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