When a truck cab lifts slowly, will not lift, or slowly sinks back down, the cause is almost always one of four things: low oil or air in the system, a leaking hose or fitting, a worn pump, or a worn cylinder seal. This page lists what to check, in the order that saves the most time.
Safety first. Never work under a tilted cab unless it is held by the safety stay or prop. A cab that sinks back down can cause serious injury.
The cab lifts slowly or does not lift
Start with the simple things. Check the oil level in the pump reservoir and top it up with the oil grade the truck maker specifies. Then bleed the system, because air in the lines makes the pump feel soft and the cab rise slowly. Look at the hoses for kinks, crushed sections or oil at the fittings. If the lever moves freely but the cab does not rise, the pump may no longer build pressure and needs a repair kit or a replacement.
The cab lifts but sinks back down
This usually means oil is escaping under pressure. The leak can be inside the pump (a worn valve or seal), inside the cylinder (a worn piston seal), or outside at a hose end. If you see oil on the outside, follow it back to its source. If everything is dry on the outside, the leak is internal and the pump or the cylinder needs new seals or a replacement.
Where is the oil coming from?
Oil at the pump body points to the pump. Oil around the cylinder rod points to the cylinder rod seal. Oil at the end of a hose points to the hose or its fitting. Wipe everything clean, pump the cab up once, and look again. The new oil shows you exactly where it starts.
Repair or replace?
If the body of the part is in good condition, a repair kit often solves the problem. If the body is cracked, the rod is scored or the thread is damaged, replacing the part is the safer choice. We supply pumps, cylinders, hoses and repair kits, so you can choose either way.
What to send us
Send the OE number from the old part, the truck model and year, or a clear photo of the part. We will confirm the right replacement before you order. You can also look up OE numbers in our lists: cab tilt pumps, cab tilt cylinders, cab tilt hoses and repair kits.
OE numbers and truck brand names are for reference only. RHAP parts are aftermarket parts, not original parts from the truck manufacturers.
Wenzhou Ruiheng Auto Parts (RHAP) supplies aftermarket cab tilt pumps, cab tilt cylinders, hoses and repair kits for European heavy-duty trucks, including Volvo, Mercedes-Benz, Scania, MAN, Renault, Iveco and DAF. Send us the OE number, VIN or a photo and we will confirm the right part before you order.