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Three Mechanics, Three Opinions

Hi all,

Three mechanics have given us three different opinions about what is wrong with our 2003 Nissan Sentra. I'd like to hear from the Car Talk community.

The problem started when our car began to shake when we drove above 40 miles per hour. We got the radiator replaced. However, the car still would not always start.

We took it to the Nissan dealership. The mechanic there said it needed a new fuel pump.

We took it to mechanic #2 for a lower-cost fuel pump replacement. However, the car has started every time for them. So they cannot be confident that there is something wrong with the fuel pump. The fuel pressure does drop off after turning the key off. This mechanic said our main problem is that there is antifreeze in cylinders No. 2 and 3 of the engine (likely from when our radiator broke). There is either a crack in the cylinders or the head gasket has failed. They are estimating $1,200 to $1,600 to fix this. They said if we don't take care of this, the antifreeze will continue to circulate and damage the engine further.

The Nissan dealership says if there were antifreeze in the engine, the check engine light would have come on. Also, they say they would have noticed if there were antifreeze in the cylinders. Their opinion is the fuel pump is only thing that needs to be fixed.

We then called mechanic #3 to get another opinion. This mechanic specializes in Hondas/Toyotas/Nissans. He hasn't looked at the car yet, but he thinks that the motor could be damaged since the car was shaking when the radiator broke. He says he thinks it is unlikely that the fuel pump needs replacing, and he thinks the check engine light would not detect the antifreeze in the engine.

Fuel pump, antifreeze in cylinders, or motor? Or all three? What do you think?

The car has about 85,000 miles on it.



  • edited February 2013
    How fast does the fuel pressure drop off after the key is turned off?

    And it's true. If there were coolant in any of the cylinders it would cause a misfire in the engine and turn the Check Engine light on. Plus there would be steam coming out of the exhaust pipe as the coolant evaporated out of the cylinders.

  • I think I agree with fuel pump.
  • It may be possible that you're getting antifreeze in the cylinders, but you would have bright white smoke from the exhaust. As it was said before, it would also cause a misfire and throw a code.

    If you have enough antifreeze in the cylinders, that can also cause a no-start problem. When the car was failing to start, would it just turn over and over with no luck, or would it sputter and attempt to start?
  • Was the car allowed to overheat?
  • edited February 2013
    This is not making sense. You got the radiator replaced because the engine was shaking? Is there a paragraph or two missing there somewhere? After the radiator was replaced, the car still won't start, another paragraph missing? The fuel pressure drops off and they found antifreeze in the cylinders, two or three paragraphs missing?

    None of these things are related with the exception that if the fuel pressure is dropping off after turning off the key and the engine not always starting. That would indicate a leaking injector that is flooding the engine making it hard to start. It might also make it run rough but should set a code.
  • @keith it's buried in there, when mentioning mechanic #3

    "the car was shaking when the radiator broke"
  • A lot of story missing here; a lot.

    It would be interesting to know if the dealer charged them a fee or not for any diagnosis. Having something diagnosed and then taking the car away to "get it done cheaper somewhere else" can be a real irritation to put it mildly.

    It could well be that this car has multiple problems but determining if the engine is even worth saving should be the first step.
    If the anti-freeze in the cylinders is true and based on the radiator comment it could be that it's semi-fried at least.
  • if the fuel pressure drops quickly when the engine is shut off, that's likely the check valve inside the fuel pump is faulty. this can cause a hard start/no start condition when hot as the fuel in the rail boils off. if there is coolant in the cylinders, it may not be bad enough to cause a misfire all the time. recommend a cylinder leak-down test for cooling system leakage, and you may need a pump, too. i wonder what else is wrong, is it still shaking?
  • It seems like the first thing you need to determine is whether or not coolant is in the cylinders. Besides reading the ECM codes, there are various tests shops can do that can determine whether there is any path between the coolant and the cylinders. One is called a "leak-down" test. Another tests the chemistry of the coolant itself for signs of exhaust gasses. And they might suggest a compression test. I wouldn't expect any of these tests to be super-expensive. Maybe ask if one or more of these tests be done to confirm/disprove the coolant-in-cylinder theory.

    Once you know that, one way or the other, then you'll have the knowledge you need to procede.

    Best of luck.
  • I would suspect the radiator leaked out most of the coolant causing an engine overheat and head gasket failure. The shaking was the misfire in the affected cylinders due to coolant in the cylinders.
    Or, the engine overheated then blew the head gasket and the pressure created popped the radiator. Either way find out definitively if there is water/coolant in the cylinders.
    Good luck
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