Here's the scoop. I have an '84 SE with a rebuilt motor, I have been going through about a gallon of coolant a month. So I started with the obvious. Old radiator, replaced, water pump, replaced, heater core, replaced, all lines have been inspected and are bone dry. There is no coolant in the oil, and I have a new radiator cap, expansion tank and hose. Then I thought it could be the head gasket, so that got replaced. No change, then I thought the intake gasket, no change. Then I started watching the exhaust very carefully. There are times that this thing will fog the neighborhood, with white smoke, but most of the time it appears normal, and there is no correlation between how full the coolant system is. I know the coolant goes into the intake, does it get up into the throttle body at all? I am convinced that there has to be a crack somewhere or if the coolant does heat up the throttle body the gasket could be bad. The car runs great gets great mileage, and has no miss. The RPMs are high when cold (2500) but when the engine is driven for 10-15 minutes the idle comes down and bounces between 700 and 1000.

Any thoughts, has anyone had this problem?

Rich

Did you have your head checked when you replaced the gasket? Duke heads can crack.
Quick test: With the engine cold, run the car for a few seconds, shut the engine off, then remove the thermostat cap. If there is any pressure released, and/or any fluid (other than a few drops) comes out, you have a problem. If it's not the gasket, it has to be a cracked or warped head.

quote Originally posted by TopNotch: Did you have your head checked when you replaced the gasket? Duke heads can crack. Quick test: With the engine cold, run the car for a few seconds, shut the engine off, then remove the thermostat cap. If there is any pressure released, and/or any fluid (other than a few drops) comes out, you have a problem. If it's not the gasket, it has to be a cracked or warped head.

I did not have the head checked when I had it off. I did check to see if there was wobble when I had it all cleaned up and before I put the gasket in, and it seamed to sit flat. One thing I forgot to add, after I replaced the head gasket, and discovered I was still going through coolant I pressurized the system and noticed that there was coolant in the intake under the throttle body. That is what prompted me to replace the intake gasket.

Rich

Maybe your intake manifold is cracked or breached somehow. Are there any home-made mods on it that involve drilling?

Head gaskets go in dry. Sealers can cause big headaches.
Bolts torque spec is only for Clean Dry threads unless FSM said otherwise.

Use FEL-PRO MS90563. Is made to resist engine from sucking coolant into #4 cyl.
if that happens #4 plug will not look same as others.

if intake, gaskets, or head has failed look for plug(s) look different.
Normal plugs have a little carbon.

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[This message has been edited by theogre (edited 08-24-2015).]

UV coolant dye and a UV light.

Sounds like a crack, most likely in the intake manifold or the head between the valves. It's also possible the block itself is cracked.

The loop into the intake is to keep it from freezing in the winter. Bypass it for now while warm and see if the loss goes away.

Can coolant get from the head to the intake? When I had the head off it looked like cylinders 3 and 4 were getting the coolant. What bothers me is I could see the green below the throttle body. So I am leaning towards an issue with the intake. If there are no passages through the throttle body, then the throttle body gasket isn't the problem. I guess I will have to hunt down another intake and see if that cures the problem. Just a note on the rebuild it is so fresh you can still see the honing marks on the cylinder walls.

Rich

I suppose anything is possible but I don't beleive coolant to the intake from the head is, and I think you coolant would be gone in short order. There are 2 hard pipes that connect to each side of the throttle body that just may not be tight enough if you are finding coolant below it. Warm the car up shut it off with the I intake tube off and look around.

quote Originally posted by silver 85 sc: Can coolant get from the head to the intake? When I had the head off it looked like cylinders 3 and 4 were getting the coolant. What bothers me is I could see the green below the throttle body. So I am leaning towards an issue with the intake. If there are no passages through the throttle body, then the throttle body gasket isn't the problem. I guess I will have to hunt down another intake and see if that cures the problem. Just a note on the rebuild it is so fresh you can still see the honing marks on the cylinder walls. Rich

[This message has been edited by LornesGT (edited 08-28-2015).]