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Over heating frontier

Ok… My 2001 Nissan frontier xe… Has a V6 non super charged engine. I have over 138k on it and after a major service it began to overheat on me. A visit toy mechanic 2 months after revealed a worn by pass hose, it was replaced. The water pump was also replaced at the service.

The past three weeks the vehicle continues to overheat. I have replace the thermostat, several hoses, clutch fan, radiator and sensors . After all this still have bubbles in the radiator. I have had two pressure test and two checks for co2 in coolant both were negative … The engine runs like a champ … No smoke no sputtering purrs like a kitten… Yet after a drive on the high way 40 to 60 mph… I end up with it over heating and bubes in the resivior tank. There is mo coolant in the oil and no smoke coming out the exhaust …Help!

Radiator cap? You did put on a new one when you replaced the radiator, yes?

Radiator Cap ? So, You Think It Could Be A Bad Cap That’s Causing The Engine to Overheat ?
Are You Kidding Me ?

I’m just joking. You very well could be correct.

Nissan agrees with your theory, too and in 2004 they issued a 3 page Technical Service Bulletin (with 5 cap photos) for their technicians that discusses radiator cap inspection / replacement in 1999 and later Nissan models in regards to over heating. Caps have been found to have the black rubber sealing gasket (seals against radiator neck) swell up and lose sealing ability.

The seal diameter should be a little smaller than the metal plunger that backs it. Also, it needs to be free of any waxy residue or foreign matter. The neck should be clean and free of the stuff, too.

"I have had two pressure test and two checks for co2 in coolant both were negative …"
But, was the cap’s operation to confirm that it opens and closes at the correct specifications as Nissan recommends, a part of the tests ?

Why not just replace it [with an OEM part or better] as Cigroller has recommended if it hasn’t been replaced recently ?


Ok… I had a new cap with the old radiator… It transferred over to the new radiator… I did buy a new cap though… A fancy one that had a release… Still same results. My radiator was new from Radiator Barn and that was a self install along with a new failsafe thermostat… I gonna pull some plugs and see if I got any residue on them… I think water pump… My mech says bad head gasket… I think because he installed the water pump… The old one was working just fine…

Chances Are That Your “Mechanic’s” Latest Guess Is A Good One.

Tell us how these pressure tests were performed.


I am not sure… I went to two different garages and had it done…I had the dye test (done twice at my mechanic and a test that measures exhaust gases at the other ) both stayed the were negative …

I gotta kinda agree… But I there are afew threads about leak on elbow that connects the bypass hose … It only overhears in the heat of the day…is that a factor?

I will know on Monday if I have foul plugs… That by the way were changed with my service in April …I am hoping it wasnt a head gasket because of all the changes I had done prior to my service. That started a with a check engine lite which required a new gas tank and a exhaust gasket …so I did the service also in April … I have too much invested in this truck to give up now and it has been a great vehicle for me…

Hey…leaky head gasket is the result… How do you perform a pressure test and why does it take so long to find a leaky seal…!?

Sometimes a head gasket will only leak at highway speed. It doesn’t build up enough pressure to leak at an idle. The test for exhaust gas in the coolant should have caught that though.

Yeh… I can’t Why that didn’t happen… The only reason. My mexhinc found the leak is by leaving it under pressure (coking system ) over night…does that sound right? He also found that my lower hose was leaky… This is test would have made 6 tests over a week and a half proped . I has already changed the top hose after putting in a new radiator. I learned a good lesson there change 10 year hose no matter what people think, they don’t last forever.

My mech stated he did it over night does that sound right?