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2000 Hyundai Elantra Overheated

My daughter’s Elantra overheated. The radiator was replaced along with the thermostat. The engine runs well and the compression test results were good (# 1 - 145, #2 - 150, #3 - 150, #4 - 155). Given that information could we have a blown head gasket?

Also I would like to get some help in changing out the fuel filter. I cannot figure out how to remove the bottom (input) fuel line. The top one just pops out after you remove the screw. The bottom fitting is obscured and I don’t know what to do. There is a 19 and a 17 mm hex head down there but nothing wants to give.

Those figures don’t point to a blown head gasket but I don’t know anything about your filter. If you are trying to remove a bolt and it won’t budge , you need more leverage, piece of pipe or a box wrench over your ratchet or breaker bar.

I’m not a Hyundai guy and can’t tell you exactly what to use on the fuel filter to remove it.

Is there a particular running problem or issue with coolant loss in regards to the question about a possible head gasket problem?

The compression results are so-so. Odds are if the compression is retested as a wet test you will see those numbers go up. If so, this means piston ring problems and the oil level should be monitored closely to make sure it’s not blowing through oil quickly.

Yes, it’s possible to have a failing head gasket with good compression readings. It doesn’t take very much of a breach to cause a small amount of coolant loss and lead to overheating. Often the breach is not enough to be picked up with the results of a static compression test. But there are also a dozen other reasons that can cause overheating and other ways to test for a bad head gasket. You may have more than one problem. For example a stuck thermostat can lead to overheating which in turn can cause a failed gasket or cracked or warped head. There are endless possibilities. I would pressure test the cooling system with the spark plugs out for several hours or overnight and tell you the results.

As for the fuel filter you just need a couple of wrenches and the strength to loosen the nut.

There is another type of compression test called a “leakdown test” that can definitively determine if there’s been any headgasket damage. It’s s proceudure wherein the crank is rotated until the valves are both closed, air pressure is pumped in through the spark plug hole, and a gage is used to measure the amount of pressure loss in the cylinder. Excess loss points to a possible headgasket breech. A kit is available affordably at any parts store, comes with instructions, and the test should be easy to perform on this engine, it being an inline 4 transversely oriented. You may want to consider this.

There is a chemical block test that can confirm a bad head gasket. Usually if the head gasket is bad the car will overheat on the freeway or when you get off the freeway.

Were you thinking of the chemical test that detects the presence of hydrocarbons in the coolant?
I agree that that is a good first idea. If there is presence, there’s no need to confirm with a leakdown test. If hydrocarbons are detected, it’s a safe bet that there’s a breech.

You can also “borrow” a block tester from the loaner tool programs at many of the auto parts stores. You will have to foot the bill for a bottle of the fluid though (I think I paid $10 for one once). Note that using one involves draining coolant and running the car with the radiator cap off. If you’re not comfy working on cars you might ask a shop to do it.

And I’m curious about the sequence of events because the post is a little vague. The car overheated, so then the radiator and thermostat were replaced but the car still overheats? Is that the issue? Are you sure the system was bled of all air? Are the cooling fans working? Does it only overheat at specific times/conditions? You might also wonder about the water pump.

Were those compression results cold or hot?

As long as it isn’t overheating or leaking now the radiator and thermostat have been replaced, I think the best course of action is just to drive it and see if any symptoms develop. It’s possible you got lucky and the overheating wasn’t severe enough to do any damage. In the meantime monitor the condition of the oil and coolant to see if there is any mixing between the two going on.

I recently replaced the fuel filter on my Corolla. The filter is vertically oriented on the firewall. The top connection came off easily, but the bottom was more difficult. The only access is through the front wheel well, and it is difficult see what I was doing. On a lift it probably wouldn’t be a problem, but working on the ground it wasn’t so easy. I ended up using a mirror. I tried various wrenching combos and eventually by trial and error found it easier using a crows-foot ratchet accessory. A helper holding the filter side steady aids the wrenching situation too.


You need to use line wrenches to remove that fuel filter

Open end wrenches will possibly round off the fitting without loosening it

Here’s an interesting question

Are you absolutely sure you’re actually trying to loosen the fuel line fitting?

Remember . . . the fitting is on the bottom, so you have to think upside down

One more thing . . . the filter itself has a 19mm hex. Don’t try to loosen that. Hold the 19mm hex with one wrench. Then loosen the 17mm fuel line fitting with the line wrench.

Good luck!

Is a “line wrench” the same thing as a “flare” wrench @db4690? I think there are crows feet versions of that type too.