VOLVO Repair Manual - Table of Content [200] [700] [900]
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2.10 VOLVO Radiator, Water Pump, Fan, Thermostat

2.10.0 VOLVO Cooling Troubleshooting Guide, Finding a Leak, Draining the System

2.10.1 Water Pump

2.10.2 Radiator

2.10.3 Thermostat

2.10.4 Hoses

2.10.5 Electric Fan

2.10.6 Engine Fan

2.10.7 Temperature Sensor

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2.10.0 VOLVO Cooling Troubleshooting Guide

The troubleshooting procedure below applies to all volvo models and probably to all cars with a water cooled engine. The idea is to carefully observe the temperature gauge in the instrument panel to diagnose most cooling problems with your car. The table below covers all cases to determine if its the gauge itself, the radiator or any other part of the cooling system that needs to be fixed.

Figure 2.10.0a Engine Temperature Gauge is item # 5 for this car model.

The Procedure below will work for all VOLVO models

Temperature gauge is not moving, needle rests at left whatever the engine temperature
  • On a VOLVO 740/760 hit the dash above the instrument panel; the needle sometimes sticks (also applies to fuel level needle)
  • Check the connection of the water temperature sensor on the engine head, most probably the wire broke and is disconnected. See temperature gauge sensor for instructions.
Needle rises with ignition key in on position and a cold engine (before it is started) OR intermittently jumps high quickly
  • Check the connection to the water temperature sensor on the engine. The wire is most probably cut and touching the engine. It is rare for the sensor to fail.
After the engine warms up the needle is always steady but lower or higher than center
  • The thermostat is not the correct rating. Having this issue 'develop' points to a future thermostat failure, and it should be replaced.
    In warm climates some drivers prefer to run their cars a little cooler to avoid overheating. In colder climates some drivers prefer to run their cars a little warmer to heat up faster. However, consistently running a car cooler wears the engine faster.
When the engine warms up the needle continues to rise until into or near the red zone. Can reduce the engine temperature slightly by switching the cabin temperature to hot and running the fan on high.
  • Check coolant level and look for a leak. If you are aware of a leak (and there is no risk of freezing) refill with water until the leak is fixed.
  • If the coolant level is still high (so you are confident there is no leak), then the thermostat is not opening correctly, and it should be replaced.
  • If the coolant level is high and the cap is retaining pressure, then the radiator could have become blocked. A radiator usually leaks before a blockage is so severe that it impacts the cooling.
The temperature rises slowly when the car is idling in slow traffic, on a hot day with air conditionning ON. It doesn't overheat in normal operating conditions and returns to normal when the car moves.


Finding a coolant leak

You keep on adding coolant in your VOLVO and wonder if you have a leak ?

  • Add coolant again and close the cap.
  • Start and warm up the car.
  • Check if you have pressure in the system when the engine is warm, not too hot, slowly open the cap. If you hear air being released the system is holding some pressure. This is usually a sign that the leak is not too big. Some leaks can occur only when the engine gets warmer.
  • Check if coolant is dripping underneath the car, turn off the engine when you see drips. Check in the engine bay from above to see signs of a leak. Remove the plastic pan under the engine to see where it is coming from below. Work your way up until you find the leak.

The most common source of leaks are:

  • Radiator: damaged because of road debris or corrosion at the bottom edge or sides
  • Radiator hoses connections
  • Water pump seals or water pump shaft: they dry with time and coolant slowly starts to leak.
  • Thermostat seal ring: not common
  • Heater core internal corrosion: Inside the car, especially 740/760 and later models with an aluminium core, less common on 240 and earlier with copper core.
  • Engine head warped or blown head gasket
  • Heater hoses, smaller hoses at the back of the engine, going to and from the car through the firewall

If you know you have a leak but there is no coolant underneath the car, suspect the heater core. Signs of a heater core failure are the smell of coolant inside the cabin, a foggy windshield, a pool of water on the front floor mats, or a soaked carpet. You can slow the leak by keeping the cabin temperature selector to the MIN cold position, preventing coolant from circulating in the heater core.

Cooling System Capacity, Refill, Replacing Coolant (anti-freeze)

  • Fill up the radiator via the coolant expansion tank, filler bottle. When the engine is cold, remove the cap and add a mixture of 50% coolant (anti-freeze) and 50% pure H20 water as found at the drug store.
  • The original VOLVO Type C coolant is the green/blue color, good for 2 years. Whatever the VOLVO label says on the filler tank, you can add coolant of any brand, as long as it is the same color as the tank content. Antifreeze is ethylene glycol based. You can flush and refill the whole system with a 5 years, yellow color, replacement anti-freeze (read below).
  • If you live in cooler climates, mix 60% coolant and 40% water. Check the freezing point with a coolant density tester, called an hydrometer. The freezing temperature measured with the hydrometer should be lower then the minimum temperature you will get in your geographic area. The mix should not freeze below -20 F in any case.
  • The mixture should contains at least 50% and not more than 70% anti-freeze.
  • You should drain, flush and refill the cooling system (see below) every 2 or 5 years depending on the coolant type, green or yellow.
  • The total capacity on VOLVO 4 cylinder engines is around 10US qts. or 9.5 liters. You can buy up to 5 liters of coolant and mix with 5 liters of waters. In fact some coolant always stays in the system when it is flushed, unless you drain the engine block via the drain tap (read below). The actual re-filling capacity is always less than 9.5 liters. Coolant is sold in jugs of 4 liters, so to save a few dollars you can buy a 4 liters jug and re-use some of the old anti-freeze mixture to top up.
  • Check your owner's manual for the precise coolant capacity for your engine year and model. On 6 cylinder VOLVO engines the coolant capacity is higher. Depending if you have a water cooled Turbo, automatic transmission, or factors the capacity will change.
  • After refilling the system always check for leaks.

Draining the cooling system

  • Remove the expansion tank filler cap.
  • Jack the front of the car a little and remove the engine undertray
  • On the dash set the heater temperature to hot (to ensure that the valve to the heater core is open)
  • Official procedure (not easy but minimizes loss of coolant)
    • Open the drain tap(s) on the engine block. On 4 cylinder engines: 1 tap, on the right hand side of the engine, back and above the oil pan. It is not easy to reach because its blocked by the exhaust pipes below and all the exhaust manifold above. The car must be jacked up safely. Once the drain tap is loose connect a piece of garden hose to the tap and place the other end in your catch pan. On 6 cylinder engines: 2 taps, one on each side.
    • Disconnect the lower radiator hose using a 7mm socket or flat screwdriver, and allow the rest of the coolant to drain. Disconnect slowly and try to catch as much coolant as possible by moving the catch pan in the correct place.
  • Unofficial procedure (what everybody actually does)
    • Place a catch pan under the front of the engine
    • Undo the bolt retaining the radiator expansion tank.
    • Undo the top small hose on the expansion tank
    • Raise the expansion tank and tilt it such that coolant is leaking from the small hose connection into your catch bucket.
    • Raise the tank and undo the small hose under the expansion tank using a 7mm socket or flat screwdriver. Hold up the hose end and slowly lower it until coolant leaks out , into your catch bucket. If you need to replace the water pump, thermostat or heater core you can stop here. The coolant level is low enough.
    • Disconnect the lower radiator hose using a 7mm socket or flat screwdriver, and allow the rest of the coolant to drain. Disconnect slowly and try to catch as much coolant as possible by moving the catch pan in the correct place
  • Store and re-use the old coolant if not older than 2 or 5 years, depending on its type and color: green coolant is good for 2 years, the yellow coolant is good for 5 years.
  • Filter the old coolant with a strainer to remove solid debris
  • Write MIXED on the recycled coolant container to indicate that it is already mixed with water. Re-use it without adding water, otherwise the solution is too light, the freezing point to high.
  • Dispose of scrap coolant in an appropriate container and safely store until the next toxic waste recycling day in your area.
  • Refill the cooling system


2.10.1 Water Pump

The function of the water pump[1] is to circulate the coolant through the engine and radiator. The water pump is belt driven and located in front of the engine. It is important to fix water pump leaks, because of the close proximity to the timing belt and alternator on some models. Coolant leaking on to these items can make for some costly and inconvenient repairs.

If the water pump is leaking from where it joins to the engine, the pump has to be removed to change the gasket [2] and seals [3]. This is a rather common problem on older VOLVO's. Once the pump has been removed most prefer to install a new pump rather than taking the risk of re-installing the old pump. If the mating surface is in good condition and the pump shaft is tight, then the pump is good and can be re-installed with new gasket [2] and seals [3].

A water pump should be replaced if it is leaking from the shaft or making noise. This is rather rare on VOLVO's. It happens when someone overtight the pulley drive belt(s). With the engine shut down, grab the cooling fan with both hands and try to push in and out, also left and right, to see any side play in the water pump shaft.

Removal Instructions

  • Drain the cooling system
  • Remove the cooling fan
  • Remove the radiator shroud and radiator
  • Loosen drive belts with the adjusting bolts and tensioning devices. Remove the water pump pulley. Push the steering pump or alternator aside to have better access to the water pump.
  • Remove the front engine timing belt cover top section (on older models it is a one part cover, you must remove the whole thing, take off the bottom crankshaft pulley)
  • Disconnect the coolant hose, going to the radiator, from the water pump
  • Undo the water pump mounting bolts
  • Pull out the small return metal tube from the back of the pump. A small round rubber seal is holding it in place. Pull the pump towrd the front to relase it.
  • Scrap off any residu left on the engine surface, make sure the mating surfaces on the engine and the pump are flat and clean.
  • Install a new gasket and top rubber seal ring. Also install the small round seal for the back return pipe on the pump. Lubricate that seal with coolant to easy penetration of the tube when installing.
  • Reinstall the pump by pushing up to compress the top seal ring on the engine head. Use a pry bar to push up while you tighten the bolts.
  • Torque the water pump bolts to 16 Ft-lbs
  • Reinstall in the reverse order. Torque the water pump pulley bolts, holding the cooling fan, to 13 Ft-lbs
  • Tighten the drive belts
  • Refill the cooling system

Figure 2.10.1a Water pump and Gaskets

2.10.2 Radiator

Radiators are liquid to air heat exchangers. They consist of a tank at each edge and tubes with fins across the middle. Hot coolant flows in from the engine at the top of one side, cools as it flows through the middle section, and drains at the bottom of the opposite side. Some VOLVOs have plastic sided radiators, these can crack from pressure at the hose fitting. Automatic transmission fluid can also flows through the radiator so a radiator designed for a manual transmission car will not fit in an automatic. However, a radiator for an automatic can be used in a manual transmission car with the ATF unconnected.
If the plastic sides are cracked, the radiator must be replaced. Some shops will rebuild the middle section if this is leaking, but compare the price of replacement first.

With regular coolant changes a flush should not be necessary. Flushing can be performed in the driveway using water or flushing products, but the outflow must be disposed of carefully. Many communities have drop off centers for small quantities of automotive oil and coolant. Garages use a specific machine, ensuring that air does not enter the system.
Be careful when working with coolant and mop up any spills immediately.

Removing the fan shroud

  • The fan shroud is retained by 2 + head screws on the inner top edge of the radiator. Undo the screws then lift up the shroud a bit and push it back to make room. To take it out of the car you must either remove the radiator (see below) or remove the engine cooling fan.

Removing the radiator

  • Drain the cooling system
  • Disconnect the electric fan temperature sensor(if fitted)
  • Disconnect the expansion tank hoses, small top hose and mid level hose using a 7mm socket or flat screwdriver
  • Disconnect the top radiator hose using a 7mm socket or flat screwdriver
  • Undo the automatic transmission metal hoses (if fitted)- rigid hoses. Spray with WD40 and let it soak. Use 2 open end wrench: one on the hose fitting and the other on the radiator to counteract the rotation. Turn slowly at first and make sure the hose fitting is turning and your are not twisting the hose too much. Rusty old transmission lines can break lower down. If it happens you can patch with a section of rubber fuel line hose from a car parts store.
  • Undo the bottom radiator hose clamp using a 7mm socket or flat screwdriver
  • Catch ATF fluid spillage into a catch pan.
  • Undo the 2 radiator top mounting brackets with a 10mm socket
  • Lift the radiator out of the car
  • The fan shroud can be taken out if necessary
  • Reinstall the new radiator in the reverse order
  • Top up the ATF fluid if necessary,
  • Refill the cooling system

Figure 2.10.2a Typical VOLVO Radiator

Figure 2.10.2b VOLVO Cooling System

2.10.3 Thermostat

The thermostat is temperature controlled to regulate the flow along the pipe. See the troubleshooting guide above to make sure the thermostat is the problem. By experience I know that they do fail. The car temperature gauge just keeps on going up, not stopping near the center, almost reaching the red zone. When you turn the inside car heater fan it reduces the temperature and you can get home. Another failure case is when the engine never warms up enough and the needle stops below the center of the gauge. Usually this is because the thermostat was replaced with a cheap aftermarket one.

The thermostat housing (Figure 2.10.3b) can become corroded and may fail to seal correctly. The housing should be replaced if this is a problem.

  • Drain the cooling system until the level is below the thermostat.
  • Coolant will spill when removing the thermostat. On a VOLVO 240 take care not too spill too much on the ignition distributor below, cover it with a plastic bag or rag.
  • Unbolt the thermostat housing from the cylinder head (Figure 2.10.3b) using a 10mm socket. Spray with WD40 to avoid breaking the studs sticking out of the housing.
  • If the housing is stuck on the engine, spray with WD 40 around the base and around the studs. Let it soak. Use a rubber hammer or small hammer and tap the housing gently sideways and upward to release it.
  • Remove the thermostat and replace with a new one, and a new seal. There is no need to use a special sealant around the thermostat or housing base
  • Reinstall in the reverse order, dont forget to put back the engine lifting hook/hole.
  • Torque the 2 nuts holding the thermostats housing to 80 inch-lbs.
  • Refill the cooling system

Figure 2.10.3a Thermostat

Figure 2.10.3b Thermostat housing

2.10.4 Radiator Hoses

Hose failure is not too common on VOLVOs because the rubber is of very high quality, but it can happen nevertheless if the clamps were overtighten for example. The best way to find a defective hose is to fill up the coolant, start and warm up the car, check under the car for a coolant leak and work your way up until you find its origin. Hoses will usually leak where they connect, for example at the thermostat housing

Removal Procedure

Figure 2.10.4.a Cooling System and Hoses

2.10.5 Electric Cooling Fan

The electric fan is mounted in front of the radiator and takes abuse from the weather and debris sucked through the grill. The fan is connected to a coolant temperature sensor in the radiator and should operate if the coolant gets too warm. The blades should be able to turn freely by hand.

Testing the cooling and its circuit

  • To test the fan itself, disconnect it from the car and using jumper wires connect the fan directly to the battery.
  • If the fan spins when connected directly to the battery then the fan is good, otherwise it should be replaced.
  • You can test that the fan circuit is actually working and the fan comes on when required. Start the engine and let the car warm up. Turn ON the air conditionning and let the car idle. The fan should start turning when the engine temperature reaches 207 to 216 degrees F.
  • If the fan doesn't come ON when it should, the problem is with the temperature sensor, the relay or the fuse for the fan.
  • Check the fuse first to see if it is burned. If the fan got stuck and not turning easily the fuse is probably blown. Check 240/260 fuse box and relays or 740/760 fuse box and relays page.
  • Locate the temperature sensor on the radiator, connected with 2 wires on the top passenger side of the radiator. Use a jumper wire between the 2 connecors and the fan should start. If it doesnt start check that there is voltage across the wires with a test light or voltmeter. Check the wires and follow them upstream to see if there is any damage. If there is no voltage across the wires check the AC fan relay and fuse again.
  • If the fan starts when using a jumper wire at the sensor connection, the problem is with the sensor itself.

Replacing the electric fan won't fix an overheating problem

The electric fan is an auxliary fan wich comes into action only in extreme conditions. Your car may have a busted fan since many years and you never noticed it. If your car suddenly starts to overheat there is no reason your should replace the electric fan. The electric fan should be replaced only if the following conditions apply:

  • Your car doesn't overheat in normal driving condition
  • You live in the southern part of the country and use the air conditionning (AC) when stuck in slow moving trafic, on hot days
  • You notice that the temperature is slowly going up when stuck in slow moving traffic on hot days, with the AC operating.

If you have an overheating problem I strongly recommend you check the troubleshooting guide to find what is wrong before replacing the electric fan.

Replacing the electric fan

  • Open hood and remove the front grill
  • Disconnect the fan at the connector
  • Unbolt the fan mouning bars/frame from the top radiator mount. The idea is to take the whole thing out and undo the fan itself from the frame after it is off the car.
  • Unbolt the fan mounting frame from the lower cross member, under the car. Jack up the front of the car if necessary to get under the spoiler
  • Spray the motor mounting nuts with WD40 and let it soak to avoid breaking the nut/studs
  • Undo the fan motor retaining nuts from the mounting frame

Figure 2.10.5.a Typical VOLVO Electric Fans

2.10.6 Engine Cooling Fan

The VOLVO engine fan is mounted on the water pump and is made of 2 parts: the white blades and the center clutch assembly. Early models didn't have a clutch. The purpose of the clutch is to limit the speed of the fan to between 3000 and 4000 RPM. There is no need for the fan to spin faster at higher car speed since the motion of the car alone is enough to cool the radiator. By cutting the fan speed it saves fuel and reduces engine vibration and performance.

The fan clutch [1] can fail. The fan should be easy to spin slowly by hand, with some resistance, it should not spin freely with no resistance. If the fan keeps on turning after the engine is shut down, the clutch is probably bad. Also check the small round spring in the front center. It should be complete and unbroken. The spring is affected by temperature, the fan should be harder to spin by hand when the engine is hot.

If the blades [2] are damaged, or of unequal length, they cause engine vibration. To replace it is easier to remove the whole fan/clutch assembly from the car, as described below. You can then replace just the white blades by undoing the 4 nuts on the front of the center clutch, the nuts shown on the picture on the right. Use a 10mm socket. Pull the blades toward the front. I recommend replacing with a good used unit. If the cluch is good dont replace it. Torque the 4 nuts retaining the blades hub to the clutch to 15Ft-lbs.

Removing the engine cooling fan

  • do not remove the fan shroud
  • do not slacken the fan driving belts
  • use a 10 mm open or box-end wrench to undo the 4 nuts retaining the fan to the water pump pulley. The best tool is a ratchet style box-end wrench
  • if the fan slips while turning the nuts grab it firmly with the other hand, or use a strap wrench, or squeeze the drive belts to block it
  • be carefull not to drop the small nuts otherwise you will have to remove the bottom engine plastic pan to find them
  • undo the 4 nuts half way, at the same time, pull out the fan a bit then undo the rest.
  • if the stud is coming out with the nut, keep on unscrewing, you will be able to put the stud and nut back in the same hole when putting it back.
  • the fan can be taken out of the car without removing the shroud
  • when putting the replacement fan in place, just do the reverse procedure. The drivebelt will tighten itself as you screw the nuts. Torque the 4 water pump pulley nuts, holding the cooling fan, to 13 Ft-lbs.
  • Adjust the drive belt tension.

Figure 2.10.6.a Engine Fan

2.10.7 Temperature Sensor for the Instrument Panel Temperature Gauge

The temperature gauge has it's own temperature sensor, seperate from the sensor used in the fuel injection and ignition systems. Erratic gauge behavior is often caused by faulty wiring. The picture on the right shows the different sensor located on the driver side of the car, under the intake manifold. They are hard to reach. The sensor for the temperature gauge in the instrument panel is the one closest to the front of the engine, left most on the picture. It is connected with a single wire. The picture was taken by removing the intake manifold but you dont need to remove it to do the repair. Just remove whatever is in your way and is easy to undo, for example on a 240 unclip the distributor cap to gain access to the sensor.

If the temperature gauge is always at the minimum the wire is probably disconnected or broken. Splice a section of new wire.

If the temperature gauge is always at the top, the wire insulation is worn and the wire is touching a metal part of the engine. Use elctric black tape to cover the exposed area.

Testing the sensor
The sensor itself never goes bad, but if you dont believe me and want to make sure remove it after draining coolant from the system. Using a voltmeter, thermometer and a pan of warm oil on a stove. Check the sensor resistance with the table below.

  Temperature Resistance
  60 °C (140°F) 217 ±35 ohm
  90 °C (194°F) 87 ±15 ohm
  100 °C (212°F) 67 ±11 ohm

Figure 2.10.7a Engine Temperature Sensors and Knock Sensor

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