Where the travel circuit ends and the vibration circuit begins on these machines is a question only the factory book settles, and this 56-page Bomag BMP 851, BW 85 T service manual PDF (OEM 008 099 37) is that book, covering the multi purpose compactor from diesel engine to central exciter. Electrical schematics take up the largest share of the pages, tracing power supply, starting, monitoring, brake and travel speed range selection circuits wire by wire. Hydraulic diagrams map the closed-loop travel pump to its motors and the vibration pump through the speed range selector valve out to the exciter. Set valve clearance to 0.1 mm on the diesel, then check your vibration solenoids Y22 and Y71 against their 2.6 A rating. Every hour spent probing connectors blind is an hour the trench sits uncompacted. Print the pages you need; they can take grease on the bench.
What's Inside This Bomag BMP 851, BW 85 T Manual
| System | Pages | Key Topics |
|---|---|---|
| Documentation | 4 | Index of Related Bomag Publications (Each Sold Separately) |
| General | 5-6 | Middle Traverse, Travel Motors, Hydraulic Oil Tank, Central Exciter, Reversing Protection System |
| List of Components | 7-8 | Engine, Travel Pump, Travel Motor, Vibration Pump, Vibration Motor, Control Valve Block |
| Maintenance | 9-12 | Maintenance Table |
| Diesel Engine | 13-18 | Valve Clearance, Checking and Adjusting the Gap Measurement |
| Travel System | 19-26 | Travel Pump, Travel Motor, Control Valve Block |
| Vibration | 27-32 | Vibration Pump, Speed Range Selector Valve, Vibration Control Valve, Vibration Motor, Central Exciter |
| Electrical Equipment | 33-42 | Power Supply, Speed Adjustment, Starting, Monitoring, Brake, Travel Speed Range Selection |
| Wiring Diagrams | 43-55 | Electrical Circuit Diagrams, Electrical Component List, Solenoid Valve (Y22, Y71) Ratings |
| Hydraulic Diagram | 56 | Hydraulic Circuit Diagram |
Quick Reference Specifications
| Specification | Value | Page |
|---|---|---|
| Inlet and outlet valves clearance | 0.1 mm | p. 7 |
| Solenoid valve, vibration (Y22, Y71) | 2.6A | p. 54 |
| Rated power DIN 6271 | 13.9 kW | p. 7 |
| Rated speed | 2800 min-1 | p. 7 |
| Valve clearance (inlet) | 0.1 mm | p. 7 |
| Valve clearance (outlet) | 0.1 mm | p. 7 |
| Gap measurement | 0.6 - 0.65 mm | p. 7 |
| Engine oil quantity | 1.3 l | p. 7 |
| Travel pump high pressure limitation | 250 bar | p. 7 |
| Vibration pump high pressure limitation | 200 bar | p. 8 |
| Engine oil filling capacity | 2.5 l | p. 8 |
| Hydraulic oil filling capacity | 38 l | p. 8 |
Bomag BMP 851, BW 85 T Common Problems This Manual Covers
Bomag BMP 851 diesel engine will not start, cranks slowly or dies after sitting overnight
Check fuel level first, then bleed air from the lines and swap a clogged fuel filter before condemning anything bigger. Test battery voltage and clean both terminals; the start lock relay blocks cranking if the travel lever is not in neutral. On the BMP 851, verify valve clearance against the 0.1 mm spec listed on page 7.
Manual Section: Starting systemMachine will not move, hydrostatic drive dead in both directions even at full throttle
Check hydraulic oil level and the charge circuit before pulling the travel pump. Tee a gauge into the high pressure side; on the BMP 851 the travel pump relief is set at 250 bar, listed on page 7. Trace the loop on the hydraulic schematic on page 20 and confirm the control valve block is actually shifting.
Manual Section: Travel System p. 19Vibration will not switch on in automatic mode, exciter stays silent at full engine speed
Test solenoid valves Y22 and Y71 before opening the exciter housing; each should draw 2.6 A, spec on page 54. Follow the wiring diagram on page 43 through the relays and switches feeding the vibration module. If the module itself is dead, bridge it and run manual vibration to finish the lift.
Manual Section: Vibration p. 27Engine overheats after an hour of work, temperature climbing on every pass
Clean the cooling fins and fan with compressed air; this diesel is air cooled and packed fins will cook it in one shift. Check the oil level and top up with SAE 15 W-40 to the 2.5 l engine oil capacity listed on page 8. Follow the cleaning intervals in the maintenance schedule on page 10 and inspect the V-belt while the guards are off.
Manual Section: Diesel Engine p. 13Hydraulic oil level dropping between shifts, wet hoses and sluggish travel when warm
Wipe every hose end and fitting dry, run the machine under load, and find the leak before topping up blind. Refill to the correct level; the BMP 851 system holds 38 l, so a wet frame rail means real volume is gone. Replace the hydraulic oil filter per the maintenance table on page 9 and recheck after the first hour back in the trench.
Manual Section: Maintenance p. 9Frequently Asked Questions
How do I adjust the valve clearance on a BOMAG BMP 851?
The valve clearance for both inlet and outlet valves must be 0.1 mm and should only be checked and adjusted when the engine is cold. The procedure involves turning the engine to the overlap position for the cylinder being adjusted and using a feeler gauge to set the gap between the rocker arm and valve shaft. p. 15
What are the replacement specifications for the engine oil filter?
The engine oil and oil filter should be changed at least once per year, and on the intervals set out in the maintenance table on pages 9-12. p. 10
What is the engine oil capacity for the BMP 851?
The engine oil capacity for the BMP 851 is 2.5 liters of SAE 15 W-40. p. 8
What is the high pressure limitation for the vibration pump?
The high pressure limitation for the vibration pump is set to 200 bar. p. 8
What is the specified gap measurement for the piston head clearance?
The specified gap measurement for the piston head clearance is 0.6 to 0.65 mm. This must be checked after changing a piston, cylinder, conrod, crankshaft, or crankcase. p. 18
What exactly do I receive with this Bomag BMP 851 Service Manual?
You get a 56-page searchable PDF that downloads instantly after checkout. Open it on your laptop, tablet, or phone, and bring it right to the shop floor.
Can I print a copy of this Bomag BMP 851 Service Manual for the shop?
Zero restrictions. The PDF is DRM-free. Print whatever sections you need to take out to the shop. Standard letter or A4 paper works.
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