Subaru Diagnostics St Helens
Two things decide what a Subaru costs you. Whether the head gaskets have been dealt with, and whether all four tyres match. Get the second one wrong and you can damage the drivetrain of a perfectly healthy car. We check both properly.
Message us about your Subaru
Send the model, engine and mileage. You will get a straight answer.
or call 01744 808586
WHERE TO START
Subaru diagnostics: a flat engine and four driven wheels
Two design decisions that shape everything a Subaru asks of you.
A Subaru is built differently from almost everything else on the road, and the two things that matter most are direct consequences of that. The engine lies flat rather than upright, and all four wheels are driven all of the time. Both give the car its character and both create requirements no other make places on you.
The flat engine is why head gaskets have the reputation they do on the older units, and why anything involving the top of the engine takes longer than you would expect. There are two cylinder heads rather than one, and they sit against the inner wings where nothing is easy to reach.
The permanent four wheel drive is the one that catches people out, because it costs money without ever showing a warning light. All four tyres have to match closely in circumference. Fit one odd tyre and the drivetrain fights itself continuously. That is not a scare story, it is how the system works. See 4x4 tyres.
HOW WE WORK
What a proper Subaru diagnosis involves
Three things that decide what the car costs you to own.
All four tyres, always
Matched make, model and tread depth. Replacing one tyre on a permanent four wheel drive car can cost you a drivetrain.
Head gasket history first
On the older flat four engines, whether this has been done and when is the single most valuable thing to know about the car.
Belt or chain by engine
Some Subaru engines have a conventional cambelt with a real interval and others a chain. None uses a belt in oil.
subaru diagnostics
SYMPTOMS
Every Subaru symptom, and what it usually turns out to be
Eight complaints that cover most of what we see.
This is what Subarus actually arrive with. The middle column is worth reading carefully, because on this make some of the expensive outcomes give very little warning.
| What the car does | What it usually is | What it means |
|---|---|---|
| Coolant or oil weeping down the side of the engine | Head gasket on the older flat four engines | Frequently an external weep rather than a dramatic failure. Caught early it stays a gasket job. See repair costs |
| Coolant level dropping with no visible leak | Head gasket, or a hose or radiator | On the engines with the reputation, this is the one to have looked at rather than topped up and watched |
| Sweet smell after a run, no warning light | Coolant escaping and burning off | Trust your nose over the dashboard here. There may be no lamp at all until the level is genuinely low |
| Binding or wind-up on tight turns | Mismatched tyres, or a drivetrain already suffering for them | The most avoidable expensive fault on the make. Check all four tyres before anything else is considered. See 4x4 tyres |
| Judder or hesitation on a CVT model | Fluid condition, or the transmission itself | The fluid is a genuine service item on these and it is regularly skipped. Worth checking before anything is condemned |
| Rough running or misfire | Coils, plugs, or an intake leak | Plugs are a bigger job on a flat engine than on an upright one, which is worth knowing when you compare quotes |
| Engine light with reduced power on a turbo | A sensor, a boost leak, or the turbo itself | Wide range of costs. Needs reading under load rather than at idle. See car diagnostics |
| Rattle on cold start | Chain or tensioner on the chain driven engines | Worth investigating rather than dismissing. On the belt driven engines, check the interval instead |
WORTH KNOWING
Never replace just one tyre on a Subaru
This is the single most expensive mistake a Subaru owner can make, and it is entirely avoidable. Symmetrical all wheel drive expects all four wheels to turn at very nearly the same rate. A new tyre is measurably larger in circumference than three part-worn ones, and the difference is enough to matter.
The drivetrain then absorbs that difference continuously, every mile, with no warning light and no obvious symptom until something expensive gives up. Replace tyres in fours where you can, and in matched pairs across an axle at the very least, with the same make and model. If you have already fitted an odd one, ring 01744 808586. See 4x4 tyres.
THE PROCESS
How we work through a Subaru
Six steps, and two of them are specific to this make.
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Model, engine and mileage
Which engine decides almost everything — head gasket exposure, belt or chain, and what is realistic to expect at the mileage. Worth establishing before anything else.
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All four tyres measured
Not glanced at. Make, model and tread depth across all four, because a mismatch here damages a healthy car silently and is the commonest avoidable fault we find.
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Cooling system checked properly
Level, condition and pressure rather than a look in the expansion tank. On the older engines this is where the expensive answers hide.
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Full system scan
Every module rather than the engine alone, and the stored conditions read before any code is cleared.
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Live data under load
Essential on the turbocharged cars, where boost and fuelling faults are invisible at idle and obvious under load.
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An honest verdict on the money
Head gasket work on a flat engine is a real job and we will not pretend otherwise. You get the figure and the reasoning. Ring 01744 808586 or see repair costs.
HEAD GASKETS
Subaru head gaskets: what actually helps, and what does not
The reputation is real on some engines. Here is the honest version.
The reputation attaches to the older flat four engines rather than to every Subaru ever built, and the failure is usually less dramatic than people expect. It typically presents as an external weep of oil or coolant down the side of the engine, or a coolant level that falls with nothing on the driveway, rather than a sudden catastrophe.
What genuinely helps is unglamorous. Keep the coolant fresh and at the right concentration, because degraded coolant loses its corrosion inhibitors and that attacks the sealing surfaces. Never let the engine overheat, not even once, since a single overheat does more damage than years of ordinary use. And investigate a small loss early rather than topping it up for a year.
What does not help is additives sold as a permanent seal. They are a way of getting a car to a destination, not a repair, and they can block a heater matrix or a radiator on the way. If yours is weeping, get it looked at while it is still a gasket job. See repair costs.
FOUR WHEEL DRIVE
Why matched tyres matter more on a Subaru than on any other car
A silent, avoidable expense with no warning light attached.
Symmetrical all wheel drive drives every wheel all of the time, and it expects them all to be turning at very nearly the same rate. That expectation is built into the mechanical design rather than managed by software, which is precisely why it matters more here than on a part time four wheel drive system.
A brand new tyre has a larger rolling circumference than a part worn one. Fit one new tyre against three half worn ones and the drivetrain has to absorb that difference continuously. There is no warning lamp, no message and often nothing you can feel, right up until something expensive fails.
The rule is simple. Replace in fours where you can, and across a full axle with the same make and model at the very least. Keep pressures even, and rotate if the handbook asks for it. If you have already fitted an odd tyre, it is worth a conversation rather than a panic. See 4x4 tyres or ring 01744 808586.
THE RANGE
The Subarus we see, and what each tends to arrive with
Forester to BRZ, and the faults that follow each.
We are on Boundary Road in St Helens with a DVSA test bay on site. Subaru owners tend to keep their cars a long time, which suits how we work.
Forester
The one we see most. Head gasket history matters on the older ones, tyres matter on all of them, and they last extremely well when looked after.
Impreza
Ranges from ordinary to very quick. On the turbocharged cars, boost and fuelling faults need reading under load rather than at idle.
Outback
Used as a working car by most owners, so mileage is high and condition underneath matters as much as anything electronic.
XV and Crosstrek
Newer, chain driven and generally undramatic. CVT fluid condition is the item most often skipped on these.
Legacy
Older now and worth keeping when the engine has been sorted. We will be straight about whether it has. See garage services.
BRZ
Different again, and driven accordingly. Fluids, brakes and tyres wear at the rate the driving deserves rather than the mileage.
COST
What it costs, and the free check that matters most
A fixed price to find it, and honest arithmetic on the big jobs.
The diagnostic is a fixed amount, quoted before you commit, and where a repair goes ahead with us it folds into the job. On a Subaru we will also give you something that costs nothing: an honest view of the tyres, because that is the fault most likely to cost you money without ever announcing itself.
On head gasket work we will not pretend it is a small job. The engine layout means real labour, and quoting it cheaply then finding more is not how we work. You get the figure and the reasoning before anything starts, and you are free to think about it.
A set price to find it
Told to you before you commit rather than billed by the hour, so nothing is open ended.
Tyre check included
All four measured and compared as part of any diagnostic. It is the cheapest thing we do and the most valuable on this make.
Head gasket priced honestly
A real job on a flat engine, quoted properly rather than optimistically. See repair costs.
No sealing additives
We will not put a bottle of something in your cooling system and call it a repair. If you want that, we are the wrong garage.
Spreading a larger bill
There is Payment Assist where the work is genuinely worth doing, on a soft search rather than a full application.
A straight view on the car
Whether an older Subaru is worth the gasket job is a fair question and you will get a fair answer. See contact us.
ALSO HERE
What else we do while the Subaru is in
One visit rather than three, and nothing added that did not need doing.
- Tyres, in matched sets — The single most important consumable on a permanent four wheel drive car. See 4x4 tyres.
- MOT on site — A DVSA test bay here, so a fault found becomes a repair and a pass the same visit. See MOT.
- Servicing — Including coolant condition, which on the older flat four engines genuinely matters. See car servicing.
- Cambelts — On the engines that have one, at the proper interval. We will tell you free which yours is. See which cars have a wet belt.
- Batteries — Tested properly rather than swapped hopefully. See car battery replacement.
- Talk to us first — Ring 01744 808586 with the model and mileage, or contact us. Tyre advice is free.
Owner questions
Subaru owner questions, answered
Fifteen questions Subaru owners actually ask us. If yours is not here, ring 01744 808586.
Three things, and none of them is a product you pour in. Keep the coolant fresh and at the correct concentration, never let the engine overheat even once, and investigate a small coolant loss early.
Degraded coolant loses its corrosion inhibitors and that attacks the sealing surfaces over time. A single overheat does more harm than years of normal use. See car servicing.
On a flat four the heads sit against the inner wings with very little room, which is why this question comes up at all. What is realistic depends on the engine and the car.
What we will not do is quote it cheaply on an assumption and find more later. You get an honest figure and the reasoning before anything starts. See repair costs.
On the older flat four engines that is the symptom worth acting on rather than topping up and watching. It frequently presents as an external weep or a slow loss with no warning light.
A sweet smell after a run is another sign, and your nose is more reliable than the dashboard here. Ring 01744 808586 or see car diagnostics.
Please do not without speaking to somebody first. Symmetrical all wheel drive expects all four wheels turning at nearly the same rate, and a new tyre is measurably larger than three part worn ones.
The drivetrain absorbs that difference continuously with no warning light until something expensive fails. See 4x4 tyres before you buy anything.
It is worth a conversation rather than a panic, and how long it has been on and how different it is both matter. Do not simply carry on and hope.
Bring it in and we will measure all four and tell you honestly where you stand. That check costs nothing. Ring 01744 808586 or see 4x4 tyres.
No. No Subaru engine uses a belt running in the engine oil. What varies is whether yours has a conventional dry cambelt with a service interval or a timing chain.
That split is by engine rather than model, so it is worth confirming. Give us the registration and we will tell you free. See which cars have a wet belt.
There are products sold for that and we will not use them. They are a way of getting a car somewhere, not a repair, and they can block a heater matrix or a radiator on the way.
If the gasket is weeping, the honest options are to repair it properly or to plan around it. We will help you decide which. See repair costs.
That is drivetrain wind-up, and mismatched tyres are the first thing to rule out because they are by far the commonest cause and the cheapest to fix.
If the tyres are matched and it still does it, then something in the driveline needs looking at properly. Either way it needs measuring first. See 4x4 tyres.
Check the fluid before anything is condemned. It is a genuine service item on these transmissions and it is skipped more often than almost anything else.
Condemning a transmission without establishing that is how people spend a great deal unnecessarily. See car servicing or ring 01744 808586.
Because the engine lies flat, so the plugs go in sideways against the inner wings with very little room to work. It is labour rather than parts.
That is worth knowing when comparing a quote to what the same job costs on an upright engine. It is not padding. See repair costs.
A set figure quoted before you commit, and it folds into the repair if the work goes ahead here rather than being charged separately.
The tyre check comes with it at no extra cost, which on this make is the most valuable few minutes of the visit. See Payment Assist for larger work.
Often yes, particularly if the head gaskets have already been dealt with, because these cars go on a long time when they are looked after.
Where the gasket job is still to come on a high mileage car, that is a real decision and you will get the figures rather than a steer. See contact us.
That is the management protecting something, commonly a sensor or a boost leak rather than the turbo itself, though it can be.
It needs reading under load rather than at idle, where these faults hide completely. Do not clear the code first. See car diagnostics.
Yes, the test bay is on this site, so anything found becomes a repair and a pass in one visit rather than two journeys.
On a Subaru it is worth combining with the tyre check, since tyres are both an MOT item and the drivetrain issue above. See MOT.
Model, engine, year and mileage, plus whether the head gaskets have ever been done. That last one changes the whole conversation on an older car.
Also when you last replaced tyres and whether all four were done together. See car diagnostics.