Blown head gasket after recent service

Two weeks ago I took my 1997 Subaru Outback in to have the water pump replaced. I normally just drive around town 35-40 mph. Yesterday I was driving about at 65 mph when the Check Engine Light went on after about 40 miles. I drove about another 40 miles to get home, then took the car in this morning to diagnose the Check Engine Light. The car ran smoothly throughout the long trip. No roughness. No peculiar exhaust or smell or steam or smoke from the engine compartment or the exhaust.

I was told that two cylinders were mis-timed and also that the car now has a blown head gasket. They also suggest replacing the timing belt, but I had that done at 60000 miles and the car has only 80000 now.

Is it possible that this head gasket problem is a result of the water pump replacement, which could have caused the timing problem , which would then have blown the head gasket as I was driving with the Check Engine Light on at high speed?

I would run very far and fast from whatever shop is blowing this smoke. No car needs a timing belt after 20K miles. I’d love to hear the story about 2 cylinders being mistimed - as if the other 2 are timed - on an engine where the timing is determined by the computer.

When the check engine light comes on error codes are stored in the computer. Find out what the exact error codes are (format: “P1234”) and post them. Also ask the shop to specify exactly what tests were run to verify a head leak.

FYI: a head leak would not be surprising on this car. Google it - they’re notorious for it.

As for the water pump - has this car ever overheated? Either leading up to the new pump or in this latest episode? If so then the odds of a head gasket issue increase greatly. But something smells very weird about this shop.

I hate to commit to any answers on this one as there are so many unknowns. The timing belt was replaced at 60k miles but apparently the water pump and tensioners were not. They should have been.

The failed water pump from a few weeks back would have ruined the timing belt so it may need replacement again.
This also brings up questions about overheating, coolant loss, and so on leading up to that water pump job several weeks back. These cars are prone to head gasket problems anyway without having it shoved along by any overheating issues.

There’s also some murkiness because you state the car runs fine, no roughness, smells, etc in the first paragraph and in the second paragraph we’re at a 2 cylinders mistimed and blown head gasket situation.
This means a rough running engine.

So what happened between paragraphs 1 and 2?

There’s a fair number of other oddities but this is already on overload.

The water pump was replaced because it was leaking. I noticed coolant on the garage floor and took it in immediately to have it checked. I was told the water pump was the source of the leak – it was corroded on the bottom. I did check that coolant was full up, so it hadn’t leaked very much. The car has never overheated–at least, I’ve never seen the temperature gauge get any further than half way up the scale.

The timing belt was replaced at Santa Monica Subaru at 58033 miles in April 2005. The parts list includes the timing belt, 4 gasket rockers, a wash rocker, 2 different gasket rockers, and 4 oil seals 32x4. I would hope that Subaru mechanics would install and tension the belt correctly, but then perhaps not.

I don’t put many miles on the car per year, and the car isn’t driven hard. Would a damaged timing belt cause the mis-timing of cylinders 1 & 2?

“What happened between paragraphs 1 and 2?” I waited for the results of the Check Engine diagnosis. They reset the error module and the error light did not re-appear. They said that the car is still cold and that they would have to drive it for awhile before running diagnostics. At the end of the day I got a call that they drove the car 18 miles before running tests and they found the two mis-timed cylinders. The person giving me the report is not a mechanic, so her explanation of how the blown head gasket was detected was confused. I wasn’t listening too carefully as I was shocked at how much this was going to cost to fix.

This independent repair shop has a good reputation, has been in business since 1974; I’ve had good service from them for years, ever since my Subaru Service moved… I’ll speak to the head guy tomorrow and get more information, including the error code, and post it.

Thanks for all your help, especially the tip to Google Subaru HG failures.
Bill

A problem with the timing belt should affect all of the cylinders, not just 2 of them.
I’m not privy to how they did their diagnosis and so on but let me pose this hypothetical. Maybe the cylinders are not “mistimed” as it’s referred to but are instead suffering an engine performance problem, or miss.

This miss could be due to incorrect valve lash, which means the adjustment on the valve lifters is too tight. Unless this is caught very very quickly and especially if it involves the exhaust valves, the valve and the valve seat may be damaged. Once slight damage occurs a proper adjustment may cure it temporarily but over time it will come back even worse. The only cure is a valve job on both cylinder heads.

Valve lash should be inspected every 30k miles and what’s downright tragic is that many shops, including the Subaru dealers, do not understand this. They follow the bogus corporate Subaru company line of inspecting the lash every 100k miles or infinity, whichever comes first.

There was a mistake made when the timing belt was replaced back at 58k miles. The water pump and belt tensioners should have been replaced at that time. That is the proper repair because at the time the water pump seals and grease in the tensioner bearings was already 8 years old and prone to fail at any time.
A leaking water pump will contaminate a timing belt and this will soften and damage the rubber. Left unattended, it will probably fail in the future by snapping or shearing teeth off

Without car in hand it’s difficult to state with 100% surety what the problem is without knowing the tiny details and so on but valve lash is at least a possibility and due to what has apparently been some service mistakes made I wouldn’t rule anything out.

(Regarding valve lash, I might reference the Subaru that came into our shop once and was barely running. The car would not even pull itself up the hump and through the door it was running so poorly We had to push it in. The problem was tight lash on the exhaust valves and both cylinder heads were trashed beyond repair. This car only had a measly 7k miles on it and that’s not a typo that should have been 70k.)

Hope some of that helps and good luck. Keep us informed.

The Subaru engine is a flat 4 and 2 cylinders (one head)can be out of time while the other is correct but the engine would run poorly if incorrectly timed on one side. As so often happens the problem is explained by the owner whose reason for posting is hoping for some help in dealing with a problem that they don’t understand. Shops don’t wish to take on training classes in automotive technology and owners want fast, cheap, easy solutions to problems. As often happens we are reading between the lines to discern the dynamics of the situation and the actual mechanical condition of the engine from the owner’s desperate and vague description. But ain’t it fun…

zassarina, was the car running normally when you drove it to the shop? When you recognized that coolant was leaking from your car you checked the coolant level and stated it was not low. Where did you check the level? ??? In the radiator or only in the overflow? But then, I am not familiar with that cars overflow/expansion tank/reservoir so it is difficult to know if the engine was driven when the coolant was critically low. But reading between the lines leads me to believe that you possibly drove the car with the coolant critically low.

ok4450: Many thanks for your detailed explanations and information. Here is the gist of my conversation with the head of the shop.

The error codes were P0301 and P0302: Misfire detected in cylinders 1 and 2. So the correct description is misfire, not mistiming.

The shop’s Subaru expert mechanic suspected a leak in the head gasket and so tested for hydrocarbons in the coolant by placing a blue liquid chemical in the expansion tank and then running the engine. The liquid turned yellow.

They will check the valve lash when they replace the head gasket.

The head of the shop disagrees that the belt tensioners should have been replaced. He offers to discuss this with you if you wish to call. Rather than post his phone number on a public forum, I’ll give it to you if you email me at aaron_poubell@yahoo.com. Just to be safe, I’ll ask to have them replaced when the timing belt is replaced.

He also said that the head gasket leak was caught early, before any real damage was done. Much more serious damage would occur if I continued to drive much longer.


The car was running smoothly in the early morning when I drove a couple of miles to the shop. After reset, the error light came on only after the car was driven for several miles.

I checked the coolant level by taking off the radiator cap and observing the fluid level, which was right up to the top. How else would you check it? ??? zazzarinO

This is all water under the bridge at this point, but it seems to me one should replace the belt tensioner if you’re doing the timing belt, along with the waterpump and all the other stuff prone to failure you can get to easily when the belt is off. Parts are cheaper than labor so it it is cheap insurance.

That being said, it doesn’t surprise me that a shop would rather do that work twice - but then, I have a learned distrust of people offering services…

I agree with the shop owner on this, I have put over 300k on an engine with its original tensioner. I have replaced numerous belts, but I have never replaced a tensioner and have never seen one go bad. In the future, I am planning to replace tensioners on the second belt change, but not the first.

I believe that if the tensioner has worked good for 60 to 90 k miles, you have a greater chance of having a problem if you do change it rather than if you don’t. Most problems with any thing occur at either the beginning of its service life or near the end. Manufacturing defects usually show up early, wear and tear show up at the end. If its in the middle of its service life, leave it alone.

If they suspect a head gasket problem then the first step is a compression test and a blown head gasket can certainly cause a misfire.
Tight valve lash can also cause misfires and this would show up in a compression test.
The oddity is that you have 2 misfires, a bad head gasket diagnosis, and an engine that you say runs fine with no smells or smoke present.

I have no intention of calling anyone or discussing anything with them. They can say what they will but they are dead wrong about not replacing tensioners and water pumps.

Many people find out, after the fact, that not doing those things is what leaves them on the side of the road with a broken belt and/or engine damage.
Your car has an interference fit engine and this means if a tensioner gives up or a water pump goes south the belt will break and then you will be looking at thousands of dollars to repair the heads or possibly replace the engine in a worst case scenario.

First, cylinders 1 and 2 are opposite each other and therefore driven off separate cams.

Then, often the overflow bottle is seen to be above the ADD mark and that is mistakenly thought to indicate that the cooling system is full.

And now, an improperly installed timing belt and/or tensioner/idler will not cause a head gasket failure. However, improper reassembly of other, ancillary components and refilling of the cooling system can.

And yes, continuing to drive with a failing head gasket would likely result in damage requiring the replacement of the engine. Immediate repair is in order.

At this point, after reading your second posting, zazzarino (please excuse my spelling error), I am somewhat reassured regarding the shops capabilities and professional ethics. And, the question of what came first; the chicken or the egg, comes to haunt us all. And I am again left intuitively thinking that while the water pump was in failure mode the engine overheated and one of the heads was warped but the damage was not apparent for some time later. But this is just my SWAG, FWIW.

Replacing the water pump – just doing that – is unlikely to cause a blown head gasket or affect ignition timing. I don’t see how it could unless something else was damaged in the process of course. There is a small chance the mechanic damaged something else by accident – it depends somewhat on what needs to be taken apart to access the water-pump – but I still think that’s probably not the reason for the blown head gasket or timing problems.

If in replacing the water pump, or before it was replaced, the engine was run without sufficient coolant and the enginer overheated, that would definitely be a reason for a blown head gasket. Usually you can see white smoke coming out the exhaust after this happens, but not always. Or sometime you can see an oily residue in the radiator, again, not always.

If as far as you know the engine has never overheated, and you’ve never seen any of the symptom above before the water pump, then there’s two likely possibilities:

  1. Your head gasket blew because it was time for it to blow. i.e. it’s normal.

  2. You have some kind of ignitiion timing problem – probably an electronic malfunction – which is either advancing or retarding the spark enough in enough cylinders to cause overheating, and it isn’t so much to cause steam or turn on the overheating idiot light, and you’re just not noticing it when it happens.

On the issue of the tensioner I agree with ok4450 - for the same reason that I’d say that the water pump should always be done with the timing belt. Your experience is a case in point. Almost of the labor to replace either the tensioner or water pump is done when doing the timing belt. And its a lot of labor. You have these replaced so that you’re not back in in 20K (or even many fewer) miles with oh…something like a leaking water pump.

I once had to replace a timing belt tensioner simply because the shop that had last done th timing belt had not. They said they only replace them if it “seems necessary” - well by the time it seems necessary its too late.

On the thread in general I’ll obviously retract almost all of my first comments as I obviously jumped the gun on short information. At this point I will say that what you likely have a very typical failed head gasket in a Subaru. Given that the head is going to coming off & its needs a water pump anyway you should just add the price of a new timing belt & tensioner in there. Its all coming apart anyway to do the head gasket. There is absolutely no point in having someone put an old belt/tensioner back on when it is reassembled. That would be the definition of penny wise & pound foolish.

A DIYer can cut corners all they want but a shop doing a professional job and being expected to stand behind the job as done correctly is a ship of fools if they think otherwise.
How many posts has there been on this forum from people who had a timing belt replaced and later on down the road ended up on the side of the road when a fairly new timing belt popped because of a leaking water pump or failed tensioner.

Gates is one of the leading producers of timing belts in the world and it could be the shop in question also used a Gates belt. Even the Gates website states the tensioners and pulleys should always be replaced to avoid potential problems.