Burns oil, blue smoke, no leak to find

A motoring publication answering owner questions about the late trucks of this generation puts it plainly: these engines tend to burn oil as the distance climbs, and the usual reason is the valve stem seals rather than anything structural — the same answer says it is not regarded as a serious fault. An owners' club thread about a mid-1990s truck losing oil with no visible leak reaches the same list from the other end, with the club's members naming valve stem seals first and then the breather system and turbo shaft wear as the alternatives worth eliminating. The two together are the shape of this problem: it is an ageing-engine trait, not a defect, and its main cost is that it is easy to ignore until the level is low enough to matter. **On the petrol engines the tell that points at the seals is timing.** Oil that seeps past a stem seal collects while the engine sits, so the smoke comes on the first start of the day or after a long wait at lights, and then clears; oil getting past the rings burns all the time, so the smoke stays. **On the diesels that reading does not carry over**, and the club thread cited here is the reason it is spelled out: it is a diesel truck, and the members answering it reach for the crankcase breather and a worn turbo before they reach for the valve stem seals, because a cold diesel smokes for reasons a cold petrol engine does not. If your truck is a diesel, work the breather and the turbo first and treat the seals as the answer that survives eliminating them. Whichever engine you have: check the level often, decide what you are willing to spend, and remember that an engine that uses oil and is never topped up is an engine that stops being fixable.

Gen 2Gen 2.51991–1999Works worseCommunity consensus

Drive normallyManeje normalmente

Community consensus. This entry is not backed by factory documentation — treat its values and steps as a starting point, not as if they came from the factory manual.

Consenso de la comunidad. Esta entrada no se apoya en documentación de fábrica — tome los valores y los pasos como punto de partida, no como si vinieran del manual de fábrica.

Symptoms

A cloud of blue smoke on the first start of the day, which then clears
A puff of smoke when you pull away after idling in traffic
The oil level falls between services with nothing dripping under the truck
An oily film inside the intake pipe or the air filter housing
A burnt-oil smell behind the truck at a stop

Likely causes

Worn valve stem seals
Blocked crankcase breather drawing oil into the intake
Worn piston rings or bores
Leaking turbo shaft seals, on turbocharged engines

Diagnostic steps

Note exactly when the smoke shows: on the first start, on pulling away after idling, or continuously under loadPoints toWorn valve stem sealsRules outWorn piston rings or bores
Take off the breather hose and look inside it and inside the rocker cover port for sludge, and check the hose is clear end to endPoints toBlocked crankcase breather drawing oil into the intakeRules outWorn valve stem seals
Open the intake pipe between the air filter and the engine and feel inside for standing oil rather than a light filmPoints toLeaking turbo shaft seals, on turbocharged engines · Blocked crankcase breather drawing oil into the intakeRules outWorn valve stem seals
Have a compression and leak-down test done on all cylinders and note where the air escapes toPoints toWorn piston rings or boresRules outBlocked crankcase breather drawing oil into the intake
With the intake pipe off, hold the compressor wheel and check for shaft play in and out and side to side, and look for oil in the housingPoints toLeaking turbo shaft seals, on turbocharged enginesRules outWorn piston rings or bores

Fix paths

Replace the valve stem seals

$$–$$$Difficulty 4/5

The seals themselves are inexpensive; the labour is the cost, because getting to them means work at the top of the engine. Worth doing at the same time as anything else that opens the same area, and worth pairing with a look at the guides — new seals on worn guides is a repair that comes back.

Clean out the breather system

$Difficulty 2/5

The cheapest thing on the list and the first to try. A blocked breather pressurises the crankcase and pushes oil past seals that would otherwise have been fine, so this can be the whole fault rather than a contributing one.

Live with it and manage the oil level

$Difficulty 1/5

A legitimate answer on an old engine, and the one the cited publication effectively gives. Carry oil, check the level at every fuel stop rather than at every service, and write down how much it uses over a known distance so you can tell steady consumption from consumption that is getting worse.

Rebuild or replace the turbocharger

$$$Difficulty 4/5

Only where a turbo is fitted and the shaft has play or the housing is wet with oil. Find out why it failed — an oil feed that was starved or blocked will kill the replacement the same way.