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Leak Into Exhaust?


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After about a half hour of driving after i turn off the car there is a knocking in the exaust right after the intake manifold but almost seems before the cat. I think it might be oil or engine coolant evaporating; i had a pressure test done and the head was said to be fine. I'm a little concerned because the coolant which was green is now a little brownish. (Note: Brand new OEM radiator professionally installed).

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They most likely didn't flush anything when they changed the radiator. They just drained the radiator, leaving all the old crap in the engine. (The drain is on the backside on the bottom. It has a little hose on it to direct it away from the frame & exhaust, awwwww) LoL!

That, or you have oil & coolant mixing somewhere. On that note, just because you asked for a compression test doesn't really mean much, *always* get the results from it.

178psig normal, 142psig minimum, no more than 14 psig difference on the same bank. If the rings are in good shape & the head gasket is new, PSIG oughta be in the mid-180's in all honesty. Doing a compression test is as easy as changing spark plugs if you're up to it. Just get the engine nice & warmed up before you start so everything that should be sealing has a chance to either seal, or unseal,

My vote:

1) flush the cooling system

2) check the oil

3) have someone else do a compression, or leak-down test that will give you numbers

AFA noises. It's pretty normal to hear exhaust parts crackle & pop from cooling down. It's just the metal, nuts, studs & bolts contracting after it's expanded so much. Even more so with stock parts as the y-pipe has the sheet metal cover with asbestos fiber all in it to insulate it. It stays real hot in there.

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Theirs a coolant system flush on the invoice so im assuming they did that as well. If its just part of the exhaust system dinging from being hot is their a way to get it to cease; since it didn't always make those noises.

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Without arguing about it, if they flushed the system correctly (key word), you wouldn't have brown coolant. (Assuming it's not oil & that it's just your basic rust from not flushing the coolant often enough).

Go buy at least a bottle of cooling system cleaner, dump the coolant out of the engine & radiator & flush it with your garden hose & cleaner. When an iron block starts to rust - you'll about never see 100% clean & clear water come out less you bust out some rust kutter & a high pressure syste, or bathe it. Just get it to be substantially cleaner than when you started & call it a day.

Takes 8.9 quarts of coolant to fill the entire system.

Reference for mixing your coolant, as always, thanks to mkiv.

% Coolant Freeze Boil

20% 16 253

33% 0 256

50% -34 265

70% -90 277

If it turns brown leakdown test on the cooling system & cylinder test the heads. Be sure to get the #'s from the tests.

An FYI, when the inhibitor packages break down in a coolant from not changing them often enough, the old iron blocks simply start rusting in the passages. The only thing you can do is flush them with a bottle of cleaner until the water from the block looks "noticeably clean". Once any of them start rusting, you can flush for hours & still turn up an orange hue here & there. Just make sure you flush it every other year.

(Since you blew a radiator, it was be extremely wise for a new thermostat & new coolant pressure caps. Water outlet cap on the intake manifold is 12.1-16.4psi, radiator should have a new cap - if not it's 13.5-17.8psi - thermostat is 190*F, fully open @ 212*F.)

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