air pump?

Air pump, eh? Now don't take my word on this, but I didn't think air pumps have been on cars since the late '60s. I thought better emissions controls took over instead of air pumps which basically just dilluted the exhaust with oxygen and such. Be that as it may, that would only make your engine work harder and get hotter. Maybe someone else here can enlighten me as to what an air pump is on a modern engine.

I was thinking maybe your "knocking" sound when you turn the car off is dieseling (it does only happen when you turn it off, right?). My '68 would do this if I put 87 octane gas in it. My uncle ran it with '87 octane all the time (moron) when he drove it and it would diesel in the summer, but usually not in the winter. Maybe since it's so hot out your car heats up to the point that it is dieseling. When you turn it off leave the car in gear (automatic, right?) and see if the noise goes away. The extra drag from the transmission will usually stop the engine pretty quick and not allow dieseling. Just something to try.

Cory

No, it's not diesling. The knock occurs when the engine is running after travelling for a while and the engine is at its hottest and when the engine cools off and restarted the knocking is gone.

Jim's reply seems very logical and I am hoping that this steam/air problem is the cause of the knocking, especially for money reasons.

I think I am going to do a complete flush and refill tomorrow trying to make sure there is no air in the cooliong system. A flush should do it.

Air pumps, or smog pumps are most certainly still around! Had a real fun time with a friend's 1985 F-250 with a 460 V8 that had TWO of those suckers (err, pumpers!) and both had failed. After removing the pumps and the ten million vaccum hoses and air injectors, the truck ran great! The truck was a California vehicle that retired to Oklahoma and so there was no smog checks on it.

-Steve

There have been many designs.

Not on a electronically fuel injected.

May just be a worn piston slapping. Hi-mileage donks can do that especially when hot.

Jason

It's telling you it's way too hot. Keep doing that, and plan on new head gaskets. Your car DID overheat. Make no mistake about it. The knocking was probably pre-ignition from all the glowing carbon. Kind related to pinging. Also, like one said, the boiling water and steam will make funny sounds too. But, myself, I think you had pre-ignition. Too hot..

Sure. It's getting way too hot. Cars talk to you if you listen..:/

It sounds like he doesn't know much either. Air pump???? Gimme a break... Thats about as bad as the clown that told my mother her camry had carb problems. If anyone sees a 92 camry with a carb, let me know so I can alert the media.

It's overheating. Do the flush, etc. You might end up needing a new radiator if it's clogged up. Make sure the t-stat is ok. It probably is...You've probably got a half clogged radiator. Also make sure the timing is not way out of whack, but I doubt that's the case also...Just something to double check.

MK

While examining the radiator before flushing it a crack was found in it. It has a plastic radiator. It was the kind of crack that didn't create a leak but was more like a squashed in crack closing off some of the radiator from operating. Being plastic it could not be soldered and boiled so I replaced it.

The car is running so cool now even in the 90 degree heat and with the a/c on the highest the temp. needle goes is half way. There has been no knocking since I replaced the radiator but I really haven't driven far until today. I am taking a ride to Atlantic City, approx. 120 miles each way and I have a good feeling that the problem has been resolved.

Again, thanks for all the replies.

Just got home and this thing is driving me nuts. I drove 120 miles this morning averaging 65/70 mph all the way there. Car ran cool. Got there, shut the car, restarted, no knock.

Drove home, same 120 miles, averaging the same speed. Ran into some bumper to bumper traffic near home but temp. gauge stayed in the middle. When I got home, shut down and restarted, _and damn_, the knock was there.

So, after a new water pump, new thermostat, new hoses, radiator and coolant and I still get the knock. Not as much as before but nevertheless it was still there when I got home. Let car cool about

I am just about to give up on this thing.

I don't like the sound of a plastic radiator... Doesn't sound conducive to good heat transfer. Anyway... Are your fan(s) working properly. That is to say, coming on when the temp is higher and/or at low speeds? Perhaps only one fan (if you have two) is coming on, or some such thing?

We're talking a Grand Marquis - 5.0 Liter V8 mounted in the traditional manner - He has one big ole belt driven fan, none of the electric jobbies.

Either this poor GM is overheating and the temp guage is lying, or this knock is something external to the engine and not the usual "knock" that most mechanics think of when something is "knocking."

Oil pressure problem, maybe? If the noise is indeed the engine "knocking."

Yeah, the fan clutch does die on these thing at times. Died on my 1987 Town Car - I could stop the blades with my hand while the car was at operating temp! Replaced it with a fixed fan - Louder, but better cooling.

"exwhyzee" wrote

Get a 2-foot long piece of vacuum hose, and stick it in your ear. Seriously.

Move the other end all around the engine compartment (without getting it caught in the fan), and you should be able to at least localize where the knocking is coming from. Or go to your local auto accessoy store, and buy a "Mechanic's Stethoscope". With that you can touch various parts of the engine, and pinpoint the noise.

Here's one now...

Jesus! A 78 Fairmont.. :-\ To each there own.