4.236 & T4.236 DIESEL ENGINES Section M: Cooling System Caterpillar

Section M: Cooling System
1.1. To Adjust the Driving Belt
2.1. To Remove and Refit Water Pump-High Position Type
3.1. To Remove and Refit Water Pump-Low Position Type
4.1. To Dismantle the Water Pump-Both Types
5.1. Inspection
6.1. To Re-Assemble the Water Pump-Both Types
7.1. Water Pump Seals
8.1. To Remove the Thermostat
9.1. Testing the Thermostat
10.1. Piston Cooling Jets
11.1. To Remove Piston Cooling Jets (Fig. M8)
12.1. To Refit Piston Cooling Jet
13.1. Nozzle Protrusion


The engine is cooled by water circulation through passages in the cylinder block and head. Circulation is by thermo-syphon action assisted by an impeller type water pump driven by a "V" belt from the crankshaft pulley.

A high or low position water pump may be fitted on the front face of the cylinder block.

The water pump bearings are pre-packed with a special grease during assembly and do not require attention in service.

A thermostat is fitted in the water outlet connection.

To Adjust the Driving Belt


Fan and dynamo or alternator belt tension should be adjusted so that it is possible to depress the belt, approximately 3/8 in (10 mm). This should be checked between crankshaft and water pump pulleys (high position water pump) or between crankshaft and dynamo or alternator pulleys (low position water pump) see Fig. M.2.

Correct tension of the fan and dynamo or alternator belt should be maintained by periodical checking and adjustment as given in Section C.

Belt adjustment is obtained by altering the position of the dynamo or alternator with an adjustable link.

NOTE: When a new belt is fitted it is advisable to recheck the adjustment after a short running period.

For those engines which have twin fan belts fitted, they should not be renewed individually but in pairs.

To Remove and Refit Water Pump-High Position Type

1. Remove fan belt.

2. Remove fan.

3. Disconnect connections to water pump.

4. Remove pump.

5. Refit pump in reverse sequence. Reset fan belt tension.

To Remove and Refit Water Pump-Low Position Type

1. Remove fan belt.

2. Remove fan.

3. Disconnect connections to water pump.

4. Remove dynamo or alternator and bracket.


5. Unscrew and remove nut and washer from stud at top of water pump. Unscrew four setscrews securing pump to cylinder block. Withdraw pump from engine (Fig. M.3).


6. To remove pump rear body from cylinder block, take out remaining setscrew, which passes through rear body only. Withdraw body from its location (Fig. M.4).

7. Refit pump rear body and water pump in reverse sequence.

8. Tension fan belt.

NOTE: With later pumps which are secured directly to the cylinder block, the lower fixing setscrew and corresponding drilled boss on the water pump body has been deleted and the joint and cylinder block modified accordingly.

The later type water pump is interchangeable with its predecessor providing the later joint is used and the lower setscrew discarded.

To Dismantle the Water Pump-Both Types


1. Remove the nut and spring washer (earlier engines may have self locking nut and plain washer) securing the water pump pulley and withdraw the pulley from the shaft (Fig. M.5), also the driving key.

2. Press water pump shaft, complete with impeller, out of the body from the front.

3. Press impeller from the shaft.

4. Remove water seal from the shaft.

5. Remove bearing retaining circlip from front of body.

6. Press out the two bearings and distance piece.

7. Remove front grease seal, seal retainer and flange.

NOTE: With some water pumps, the seal, retainer and flange has been deleted and the length of the distance piece increased accordingly.


1. Examine body for cracks, damage or corrosion.

2. Examine drive shaft for wear ensuring inner diameter of the bearings are a perfect fit on the shaft. The shaft should be renewed if the inner races rotate on it.

3. Remove rust and scale from impeller and inspect for cracks or damage. Examine impeller hub sealing face for excessive wear or scoring.

4. Examine water seal for damage.

5. Inspect bearings for pitting, corrosion or wear.

To Re-Assemble the Water Pump-Both Types

1. Press rear bearing onto the shaft, fit distance piece and press on front bearing. When fitting bearings to the shaft, ensure the shielded face of each bearing faces outwards towards the front and rear ends of shaft.

2. Fit grease seal retaining plate in position against back face of the rear bearing. This retaining plate is "dished" and when in position, the centre of the plate must not be in contact with the bearing.

3. Fit felt seal and seal retainer housing so that these bear on the retaining plate.

4. Half fill space between the two bearings with high melting point grease and press complete bearing and shaft assembly into pump housing from the front end. Position the retaining circlip in the recess of pump housing immediately forward of front bearing.

5. Fit water seal with carbon face towards rear.

6. At this stage, the shaft should be turned by hand to check for undue resistance.

7. Fit driving pulley key and press on pulley making sure there is no rearward movement of the shaft.

8. Where ceramic counter face seals are fitted, fit seal to shaft with counter face towards water seal and rubber bonded holder towards impeller face.


9. Press impeller onto shaft so that a clearance of 0.012/0.032 in (0,30/0,81 mm) is maintained between impeller vanes and pump body (Fig. M.6).

10. Refit spring washer and nut, tightening to a torque of 60 lbf ft (8,3 kgf m) -81 Nm.

Water Pump Seals

Where ceramic counter face water pump seals are fitted, if the engine is run without coolant, even for a few seconds, the heat build-up between the carbon seal and ceramic counter face is very rapid, resulting in the cracking of the ceramic. This often creates the misunderstanding that the cause of leakage is due to the incorrect assembly of the sealing arrangement of the water pump.

To Remove the Thermostat

1. Drain off the coolant and remove the hose between radiator header tank and water outlet connection adaptor, or water pump.

2. Remove water outlet adaptor and joint.


3. Remove thermostat (Fig. M.7).

Testing the Thermostat

If it is suspected that the thermostat is not operating correctly it should be tested as follows.

Immerse thermostat in water and gradually heat. Check water temperature at frequent intervals with accurate thermometer. The valve should commence to open at temperature stamped on top face of thermostat adjacent to valve seat.

Thermostats are not repairable.

Piston Cooling Jets

Piston cooling jets are fitted to all current turbocharged engines (see Fig. M8). Cooled lubricating oil is directed by means of spray jets fitted into the main pressure rail at the base of each cylinder liner onto the underside of each piston crown where it circulates, dispersing heat from the combustion area. The oil then drains back into the sump. The lubricating oil feed to the jet nozzle is controlled by a pressure relief valve fitted into the main body of the piston cooling jet assembly and comes into operation at a pressure of approximately 30 psi.

To Remove Piston Cooling Jets (Fig. M8)


Drain the lubricating oil and remove sump.

Remove the banjo bolt securing the jet body to the cylinder block.

The piston jet assembly can now be removed.

To Refit Piston Cooling Jet

The body should be fitted to the cylinder block making sure that the dowel locates correctly.

Insert the banjo bolt and tighten to a torque of 20 lbf ft (2,77 kgf m) 27 Nm.

Refit sump and fill with lubricating oil of an approved grade.

Nozzle Protrusion

If the nozzle of the piston cooling jet has been moved out of position, it is important that the condition is corrected as follows:-


With a piston removed, insert a suitable diameter tube over the jet nozzle so that it shows above the top of the cylinder bore (see Fig. M.9).

Fig. M.9 also shows the dimensions taken on the top face of the cylinder block from the extreme edges of the liner bore (X).

The tube must emerge through the top of the liner bore at a point 0.76 in (19,3 mm) from the fuel injection side of the bore and 1.25 in (31,8 mm) from the engine front side of the bore.