Losing coolant with no visible leak and bubbles in the tank
- Make and model
- Toyota Avensis (T25)
- Year
- 2008
- Engine
- 2.2 D-4D (2AD-FTV)
- Fuel
- Diesel
- Mileage
- 205,000 km
Customer complaint
The coolant level drops by about half a litre a week with no visible leak. Bubbles in the expansion tank after a drive and the temperature gauge rises on long climbs. The owner also adds a litre of oil every 1,500 km.
Fault codes
No fault codes stored.
Measurements and live data
| Parameter / measurement | Measured | Expected |
|---|---|---|
| Combustion leak test (CO2 in coolant) | Positive | negative |
| Compression, cyl. 1 / 2 / 3 / 4 | 26 / 25 / 21 / 25 bar | even between cylinders |
| Oil consumption over 1,000 km | 0.7 litre | a small fraction of that |
Tests performed
- Cooling system pressure testPressure rises with the engine running, no external leak
- Borescope through the glow plug holesHeavy carbon on the pistons; cyl. 3 crown noticeably cleaner (coolant steam)
- Head and block deck checked for flatnessBlock deck out of flat
Solution
Root cause
Head gasket failure at cylinder 3, caused by oil consumption and carbon build-up; the aluminium block deck was no longer flat.
Repair
A head gasket alone would not have lasted with the deck out of flat. Fitted a short engine with revised pistons, a skimmed and pressure-tested head, new head gasket and bolts, coolant, oil and filter. Oil consumption rechecked after 1,000 km.
Parts
Short engine, head gasket set, head bolts, coolant, oil and filter
Labour time
16 h
Lesson learned
On these engines check deck flatness before quoting a head gasket: the cheap repair often comes back.
Training case: the usual fix for this fault, not a confirmed repair on a specific car.
Did this case save you time? ipacen is free and run by one mechanic. A coffee helps keep it online.
Support ipacen
No comments yet. Seen this fault before? Add what you found.