CriticalVery commonCooling

Mazda Bongo: WL-T overheating leading to head gasket failure and a cracked head

WL-T overheating leading to head gasket failure and a cracked head is a very common cooling fault on the Mazda Bongo on the 1995–2005 cars, and we rate it critical. Putting it right costs $2,500 to $6,500 at New Zealand independent workshop rates. Below is what goes wrong, the symptoms to notice on a test drive, where to look, and what to ask the seller before you hand over any money. It is one of 6 documented faults on the Mazda Bongo.

Vehicle: Mazda Bongo
Years: 1995–2005
Fuel: diesel
System: Cooling

This page covers the Mazda Bongo as a model. Some faults only affect particular engines or build years — enter a plate below to narrow the list to one car.

All Mazda Bongo faults6 documented faults on this model

What you are looking at

Also worth seeing

What goes wrong

Overheating is the single most-cited failure on the diesel Bongo, and the usual cause is not the engine at all — it is the long coolant hose that runs under the driver's seat to the rear heater. With age it balloons and splits, the van quietly loses coolant, and by the time the gauge moves the head gasket has already gone. The WL-T does not tolerate overheating: once the gasket fails, the head very often cracks as well, and the repair costs more than a cheap van is worth. Many owners fit an aftermarket coolant alarm for exactly this reason, and seeing one already fitted is a good sign about the previous owner.

What you would notice

Coolant level dropping with no puddle under the van
Damp carpet or a coolant smell around the driver's seat base
Temperature gauge rising on hills or after a long run
Creamy sludge under the oil filler cap, or bubbles in the header tank
Heater blowing cold because the system is low on coolant

How to check it

Where to look. Coolant hose running under the driver's seat to the rear heater; header tank and radiator at the front; cylinder head

Before anything else, kneel at the driver's door and feel under and behind the seat base along the coolant hose that runs rearwards — you are feeling for damp, crustiness or a soft, swollen section, and smelling for coolant. Peel back the carpet edge there if you can. With the engine cold, check the header tank level and look at the fluid for an oily film. Take the oil filler cap off and check for creamy sludge. Then drive it properly, including a long climb if possible, and watch the temperature gauge for the entire drive rather than glancing once. Look for an aftermarket coolant alarm fitted, and ask about it. If a workshop inspection is possible: ask for a cooling system pressure test and a combustion-gas test of the coolant.

Parts involved: Cylinder head, Head gasket.

What it costs to put right

$2,500 to $6,500 at New Zealand independent workshop rates. That is for this job on its own, not for the car.

An estimate, in NZD, for the repair as normally carried out. What a specific car costs depends on which part has failed and what it damaged on the way — treat this as the floor for a negotiation, not a quote.

Ask the seller

“Has it ever overheated, and has the head or head gasket ever been done?”
“Have the under-seat coolant hoses been replaced?”
“Is a coolant alarm fitted, and has it ever gone off?”

Now check the Mazda Bongo you are actually looking at

Everything above is true of the model, and it is free. What it does not tell you is whether THIS car has been looked after: its odometer history and whether the reading has ever gone backwards, whether there is still money owing on it, whether it has been reported stolen, how many owners it has had and what it is really worth today. That comes from the official records for that plate. Enter the plate for the free details, or get the full history and a market valuation from $13.49.

Not sure what you would be paying for? See what a full KickTyres check includes.

Where this comes from

The failure described above is documented in the sources below. The inspection instructions and the cost estimate are KickTyres’ own interpretation of them.

Practical Motorhome — 'Mazda Bongo Camper Buyer's Guide'
Mazda Bongo Auto Centre — 'Overheating No More: A Mazda Bongo Engine Repair Success Story'
JDMBUYSELL Mazda Bongo buyer's guide

Mazda Bongo buyer questions

Is wl-t overheating leading to head gasket failure and a cracked head serious on a Mazda Bongo?

We rate it critical and very common on the Mazda Bongo. Overheating is the single most-cited failure on the diesel Bongo, and the usual cause is not the engine at all — it is the long coolant hose that runs under the driver's seat to the rear heater. With age it balloons and splits, the van quietly loses coolant, and by the time the gauge moves the head gasket has already gone. The WL-T does not tolerate overheating: once the gasket fails, the head very often cracks as well, and the repair costs more than a cheap van is worth. Many owners fit an aftermarket coolant alarm for exactly this reason, and seeing one already fitted is a good sign about the previous owner.

How much does it cost to fix on a Mazda Bongo?

$2,500 to $6,500 at New Zealand independent workshop rates. That figure is for this job on its own. A car showing the symptoms on this page is usually worth either walking away from or negotiating down by at least the repair figure.

Which Mazda Bongo years are affected?

Our research records this fault on the 1995–2005 Mazda Bongo. Build dates move around, especially on imported cars, so treat the range as the years to look hardest at rather than a guarantee either way. The official records tell you the exact build and first registration date for the car in front of you.