Engine Diagnosis

Can a blown engine be diagnosed without first replacing the head gasket ?

I used the terminology blown engine- but the scenario is the car ran hot and wouldn’t restart. Took it to a shop they changed the gaskets , did a pressure test ($1200) and the car still wouldn’t start. Then they said we needed a new engine $4158. They are trying to tell us there was no way to diagnose the engine without doing what they did first . Unbelievable !! PLEASE HELP I need justice!

Trying to get my money back !
Thank you

What do you mean: “won’t start”. Does it crank? Rotate by the starter motor? Or is it seized; with frozen bearings? On the ‘pressure test’ - I am assuming you mean the individual cylinder compression?

What was the compression of each cylinder? And no, you can’t check that - with blown head gaskets. However, if the engine rotates; and has adequate compression - than the reason it won’t start - is a timing /fuel / or some sensor issue. The intake manifold could also have a crack - this would allow compression - but could hinder starting. But they should have checked the manifold for that…

Overheating can also put holes into the pistons; and with blown head gaskets - this too would be difficult to determine - before work is started. But they would have seen that - once they took the head(s) off. (What type of car; year; engine size?)

If it is froze; and will not rotate (frozen bearings) - they should have figured that out; and notified you before anything else.

The information here is way too limited to be able to guess.
What gasket did they change? The headgasket?
The pressure test; was it a pressure leakdown test or a compression test? What exactly were the results?
Since they did one or the other, I assume the crankshaft isn’t bound up, so did they say exactly why the engine won’t start? If an engine has compression, fuel, spark, and everything is timed correctly, it’ll generally start.

This sounds familiar. Is this a repeat?

@thesamemountainbike yes i inquired earlier sorry but realized i didn’t use the exact wording that the auto shop guy did. hope i haven’t caused any confusion.I wasn’t sure if that would make a difference in your response or not. We were not provided with the answers to many of the questions you have posed. I do know that it was the head gasket that was changed. My Mom is 88 years old and I’m writing on her behalf trying to get information. We feel like she has been taken advantage of because she is so trusting and lacks the knowledge to ask the right questions. Please tell me what questions i should be asking and I will try to get them answered but may not have much success .The paper they gave us with the work performed doesn’t explain the diagnosis in detail. It just shows labor and parts charges and a compression test but not the results of anything that was supposedly performed. I’ll be happy to provide you with a copy.

@DS777 The car is a 2008 Mazda 3
Thanks again

Yes, an engine can be diagnosed to some extent without replacing anything. Given the overheating, a compression test should have been performed on all cylinders before any repairs were started.
Even on cylinders not affected by a blown head gasket, a piston ring problem will show up on non-affected cylinders.

Compression would have to be dismally bad to cause an engine to refuse to start with an accent on dismally.

There’s not enough info available to know what’s going on here but I would hope if they’re blaming it on compression due to a fried engine that the compression readings were written down.
I think it’s misguided, putting it politely, to not do this and lowered compression (as opposed to zero or dismal compression) should not cause a no-start condition.

Replace the head gasket, then diagnose the engine? I don’t think so. At least it isn’t a common way to diagnose a bad engine. Mechanics have various tests to diagnose questionable engines, like compression tests, leakdown tests, smoke tests, dye tests, coolant pressure tests, oil pressure tests, etc. And the first thing they’d do is simply hand rotate the engine and listen for weird noises; a lot can be told about an engine by simply doing that.

If I may venture a guess, I don’t think the head gasket has been changed. I think your mechanic has determined (possibly after replacing the valve cover gasket and maybe the intake manifold or exhaust manifold gasket) that the head gasket is shot, and with the condition and mileage of the engine, that the more frugal way to procede is with a new engine rather than fixing the existing one. To fix the existing one would require machining the head, replacing the valves, dimensioning the valve seats, and probably re-jigging the lower parts like the crank bearings as well. Instead, your mechanic will simply put in one from another car that has already been rebuilt (or from a wreck that has a known good engine). The existing engine will then be probably sent to rebuild shop that does rebuilds taking advantage of economy of scale, doing dozens of engines at a time. Cheaper that way.

If I may venture a guess, I don't think the head gasket has been changed. I think your mechanic has determined (possibly after replacing the valve cover gasket and maybe the intake manifold or exhaust manifold gasket) that the head gasket is shot, and with the condition and mileage of the engine, that the more frugal way to procede is with a new engine rather than fixing the existing one.

If that’s the case, $1200 is awfully high for replacing those gaskets!

Walknnluv, there’s no apology necessary. I’m just trying to get the facts in order to help.

I found your earlier thread. Based on that information I still suspect that the camshafts were mistimed after the headgasket replacement…if I’m correct in understanding that there was one.

Hi Guys
I now have some specific information to share regarding my earlier inquiry that was a little too vague and I apologize. Below is a description of the mechanics findings that I am seeing for the first time. I guess my question now is does this explanation sound justified for what was done?
Thank you in advance

" I diagnosed her vehicle with a blown head gasket. There was no mixed fluids and the vehicle failed a chemical block test which showed exhaust was coming up through her cooling system. Because the head gasket is such a major leak internally in the engine a compression check was not able to be done as it would not be conclusive so optimistically we performed the head gasket repair .After machining the heads and repairing the head gasket we found un foreseen, underlying internal engine damage to the engine rings due to the overheating. No diagnosis could have told us this until the head gaskets were sealed up and the work was completed. "

I believ a compression test, which they did not do, and is inexpensive to perform, could have identified ring problems. This was not the right way to go about fixing an engine.

By the way Docnick the engine is still not fixed . They wanted $4000 to replace the whole engine after doing the above work for $1200 and the car is still not running. Our issue from the beginning is how they diagnosed the engine problem.

The “lab” test, as I call it, to check for exhaust components in the coollant is legit, however I’'m not convinced that they couldn’t have determined that type of damage before proceeding. One cylinder might have had a breech, but the other three could have been subjected to a compression test.

Having said that, the deed is done. You now have limited options. Since $4000 is a big chunk of change, I’d argue with them to split the cost or pay what you owe and go elsewhere.

We’ve already paid the $1200 :frowning: and have the non-running car in our possession. Thank you for sharing your knowledge and insight

I think you need to ask friends and coworkers for recommendations for a good honest shop and have it towed there. I am a little curious how a 5 year old car got overheated in the first place. Even if the radiator cap had never been removed, the engine should not have overheated. Did she have something done to the car just before the overheating incident?

Yes she did have an oil change by this same establishment but a different location :frowning: . We initially inquired and asked if checking fluids was a part of their routine oil change and they said yes . We thought their could have been some negligence on their part and kinda still do but can’t prove it.

“Yes she did have an oil change by this same establishment but a different location”

Was it the same day as the engine failure?

She had the oil changed on January 21st and this overheating incident occured on February 19th .

hmm … well, maybe from experience the mechanic thought a compression test was bound to fail anyway, so the best course of action was to replace the head gasket. I think an argument can be made for that. Maybe folks here with more experience than I know if a leak between the exhaust gas and the coolant will always cause a compression leak on the power stroke too. If so, then it is true that the compression test before replacing the head gasket wouldn’t have been diagnostic.

They could have left the radiator cap loose so that the car lost little coolant on each drive, eventually leading to the overheating. But you won’t be able to prove it now.

The only way a compression test would not be valid in this situation would be if the head gasket was faulty and caused a combustion chamber breach in every single cylinder. The odds of this are very, very slim so a compression test is still step one.

If a compression test shows a ring problem on even one cylinder where the head gasket is not breached then the end result is the same; need of a rebuilt or replacement engine.
This falls right into the type of scenario in which a timing belt breaks on an interference fit engine and a shop states they must replace the belt at some expense to determine if any damage exists. Not so.

Sorry, but I have to disagree with their methodogy and 1200 dollars worth of “optimistically” as they refer to it could have been headed off before it even began.