Overheating, Heater Core issue

[DoubleYellow]

So I'm looking at a spider tonight, hoping that it'll be my fun 'sometimes commuter' car (I carpool with a coworker), I know it needs some work before I get there.

The seller says that it's got a bad heater core, and thus overheats after 3-5 minutes. I've read enough on here to be familiar with burping and such, I'll have to assess those needs on the ground, so to speak. But if it's a heater core issue (leaking? I don't know why a bad HC would cause an overheat, based on what I've been able to research), how do I recognize that and how tough is it to put in a new one?

Any help/ideas are appreciated.

[majicwrench]

Bad (leaking) heater core will not cause overheat, unless it is running low on coolant, cause it's all on the floorboards.

[DoubleYellow]

Bad (leaking) heater core will not cause overheat, unless it is running low on coolant, cause it's all on the floorboards.

That's what i thought too - though that's what I'm being told. I'm going to quiz the owner tonight about his rehab work on it... I'm guessing that he's never burped the system, and thus I may end up with a steal.

Okay, overheating - clearly, coolant is an issue (I can just use premix there for the short term, right?). Fan not working would be an issue, whether it would be from bad sensors or mechanically constipated. Thermostat... could need to be replaced (or, as I've been reading, could be situated incorrectly).

What else am I missing?

[azruss]

you may want to pack a new radiator cap with you. look at the condition of the hoses. they can leak under pressure. check the flange end of the heater tube that runs under the manifold for signs of leakage.

[So Cal Mark]

about the only way it could overheat in 3-5 minutes is if there is no circulation

[DoubleYellow]

about the only way it could overheat in 3-5 minutes is if there is no circulation

So bad water pump or no coolant in the first place, right?

Is there an easy way to tell if the water pump is shot?

[DoubleYellow]

Correction on the overheating issue, it's 5-10 minutes before it starts to overheat. I don't think that changes anything - actually I'd think it points more to low coolant than a bad waterpump, but I'm guessing here.

I'm thinking I'll need to flush the coolant in any case in the very near future, but any reason why I can't use basic premix to top it up for the short term?

[131]

Correction on the overheating issue, it's 5-10 minutes before it starts to overheat. I don't think that changes anything - actually I'd think it points more to low coolant than a bad waterpump, but I'm guessing here.

I'm thinking I'll need to flush the coolant in any case in the very near future, but any reason why I can't use basic premix to top it up for the short term?

You could just use water if you're going to be flushing it anyway.

[124JOE]

he may have pulled the thermostat and reinstalled it wrong
a bad waterpump ether leaks or the berring goes out and it wobbles so the belt slips

[So Cal Mark]

it's possible to have a worn out impeller on the pump, but the most likely issue is a thermostat problem

[DoubleYellow]

Okay, saw the car, and I'm tempted.

It IS a heater core issue, apparently it sprung a leak and he's not bothered to get it fixed. Therefore low coolant, therefore overheating. An easy fix would be to jump around the core for the short term (with winter approaching, fun!).

I know I could handle that, but the number of other small details that need to be addressed - I don't know if I'm ready for all of the work at this point. I've tossed the option over to my father-in-law, who has garage space and might be interested in a winter project. From what I could tell, it's mostly going to be a time-and-labor issue.

But despite all that, I am SORELY tempted. In 6-9 months, it'd be a super car to own/drive.

[DoubleYellow]

Further update: my father in law and I might end up doing this thing as a joint project.

So I need some help/advice. We need to get this thing about 10 miles. With the heater core leak (whether it's the core itself or an adjoining piece), I figure that we put the T in there to bypass the heater core. Then do a minor mod or 3 to limp it home.

How difficult is putting that T in, and where do I find the right part? 1978 spider is all I know at the moment.

Thanks!

[majicwrench]

Go to any auto parts store and buy a couple diff size flushing tees. Disconnect the lines, put it in, hope car doesn't still overheat.

[DoubleYellow]

Go to any auto parts store and buy a couple diff size flushing tees. Disconnect the lines, put it in, hope car doesn't still overheat.

Sounds like a plan. Thanks!

[vandor]

With the heater core leak (whether it's the core itself or an adjoining piece), I figure that we put the T in there to bypass the heater core.

You don't need a T.
Buy 2 feet of 5/8" heater hose, and run it from the heater pipe (the one that goes from the back of the water pump) to the long heater hose connection at the rear of the head (between cyl 3 and 4). Now you have completely bypassed the heater.

Be cautious with the metal heater pipe that goes back from the water pump. Originally they were bolted to the center exhaust manifold stud, but often that is no longer the case. Any bending of the pipe while getting heater hoses on/off may cause a leak at the front joint. To get the old hose off just cut it off, and use some lube to get the new one on, so you don;t have to push or pull very hard on the pipe.