Engine overheating

XERA

MEMBER
1994 MAZDA 626
2.0L
4 CYL
2WD
MANUAL
199,000 MILES

Motor overheats yet still blows heat. There’s no misfire or coolant leak or white smoke or oil leak and it’s burning the coolant I’m confused as what the cause could be the reservoir is still full possible sign of head gasket issue? But if so, wouldn’t the engine cut in and out all the time? It’s not doing that though it has the 2.0 liter i4 with efi paired with a 5-speed manual transmission.

5 Replies

BORIS K

MECHANIC
799 POSTS

Hello,

It sounds like the engine might have a leaking head gasket.

The best way to test for a leaking head gasket is using a chemical test. The liquid reacts to carbon monoxide and changes color from blue to yellow/green.

How to test for a leaking head gasket.

https://www.2carpros.com/articles/head-gasket-blown-test

Please let us know how you get along.

Cheers, Boris

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Monday, March 7th, 2022 AT 1:05 AM

XERA

MEMBER
3 POSTS

Head gasket is intact. Did the simple test none of it shows blown heads.

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Monday, March 7th, 2022 AT 1:07 AM

BORIS K

MECHANIC
799 POSTS

Hello,

On your initial request you stated that the engine is overheating and burning coolant.
Which test did you do to check for a leaking cylinder head gasket?

Is the cooling fan working when the engine overheats?

Cheers, Boris

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Monday, March 7th, 2022 AT 6:10 AM

XERA

MEMBER
3 POSTS

No, it is not burning coolant I had an oil test done to test for coolant. And there is no white smoke when there shouldn’t be.

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Monday, March 7th, 2022 AT 10:54 AM

BORIS K

MECHANIC
799 POSTS

Hello,

When the engine is showing signs of overheating does the cooling fan operate? At what speed?
Also does your temperature gauge show overheating?
If the temperature gauge is showing overheating is the engine actually hot?

Have you checked if the thermostat is opening?

How a thermostat works.
https://www.2carpros.com/articles/how-an-engine-thermostat-works

How to test the thermostat while still in engine.
https://youtu.be/rrcwNOxQTbE

The radiator could be blocked, impeding the flow of hot coolant.
https://www.2carpros.com/articles/how-a-radiator-works

The water pump could be faulty, not circulating coolant.
https://www.2carpros.com/articles/water-pump

How to check cooling system and water pump.
https://youtu.be/RtLhHw1wMPM

There are many reasons why an engine is overheating so we need to narrow this down a bit.

Cheers, Boris