Problem I can't pin down...

JJ71 · 03-14-2008, 08:19 AM

I have a freshly rebuilt 351C, car is a 1971 Torino GT. It starts and runs perfectly. I let it run for about fifteen minutes while adjusting carb, checking timing. When I turn it off it keeps making a popping sound right at the thermostat, like its opening and clossing hard,(and fast, but not regular interval repetition) I replaced thermostat thinking that the parts store sold me a bad one, does the same thing. Swapped the waterpump also. No difference. I ran it without thermostat to make sure that it was pumping water, and it is, Also have a brand new aluminum radiator. The thing that bothers me is that the noise sounds mechanical, but doesn’t start until the water heats up. None of this happened prior to rebuilding, what could be wrong? Sratching my head here. I would really appreciate any direction you guys could offer. Thanks !

jonmark1985 · 03-14-2008, 10:03 AM

no clue, could you post us a video or a sound recording of the noise. Also you can use a mechanics stethoscope to pin point the noise better, or a large screw driver will work.

JJ71 · 03-15-2008, 05:08 AM

I've been all over it with a stethoscope. Its right at the thermostat.

jonmark1985 · 03-15-2008, 07:08 PM

you put a new timing chain in it right?

FistyFetiva · 03-16-2008, 10:22 AM

Quote:

Originally Posted by jonmark1985

you put a new timing chain in it right?

Does this have a EGR reactor valve? As I remember they were mounted close to the thermostat on the front of the motor under the air cleaner. It could be the vacuum diaphragm releasing the reactor valve. After the rebuild you must have more vacuum and the valve may have been stuck before. I had a 1974 SAAB 900 with just over 400k on it that did that until I found someone who knew SAABs. All I had to do was take the valve off and clean the carbon and all was good. Sorry for saying the "SAAB" word in a Ford forum.

JJ71 · 03-17-2008, 10:11 AM

Yes. New everything. Okay, except breather and block. :-)

JJ71 · 03-17-2008, 10:51 AM

I had heard of something similar to that happening before, however; there isn't one on this year ('71) Torino. I think that those were put on in ,73.

FistyFetiva · 03-20-2008, 12:32 PM

Quote:

Originally Posted by JJ71

I had heard of something similar to that happening before, however; there isn't one on this year ('71) Torino. I think that those were put on in ,73.

I was talking to a Ford mechanic friend of mine about my Festiva and happened to mention this mechanical noise your having. What he told me is this. It's possible the head gasket is leaking. Since there's more pressure from the cylinder to the water jacket than the other way around, the popping your hearing could be exhaust gases escaping passed the gasket and through the thermostat. He said there's a test you can run and it takes a special gauge that most repair shops have. It checks for exhaust gas in the cooling system. He also mentioned it could be one of the front valve lifters, it may have a faulty valve in it, but he doubted it. This guy has been in the business since the before the old reliable 352 came out.