74 Mini 1000

Sweet!

I changed the oil this morning and went for a drive. In less than a mile it was overheating. It will cool down to normal quickly when cruising in 4th but when accelerating the temperature goes up fast.

Is there a clutch on the fan? Radiator flushed?

Still running well I hope?

No clutch on the fan. Radiator was flushed.

It runs better, I just don't want to overheat it and cook the headgasket again.

When I take the oil filler cap off it pushes air out of the filler hole...not so good.

Also it only blows cool air out of the heater.

Heater core clogged or a big 'bubble' in the cooling system?

Does it have any kind of PCV system?

it has a crankcase breather which is likely clogged. I've run out for quite a while with the radiator cap off to get rid of any bubbles.

Is the coolant actually flowing?

You'd be amazed at how well some older designs would work with no water pump impeller.

it appears to move around in the radiator when I have the cap off, I could hear it agitating the coolant when I had the radiator off and spun out by hand. It could be slipping at higher rpm though.

I hate to sound like a broken record, but double (triple?) check the timing again. If the timing is off (retarded, I think, but maybe too advanced), the engine will run hot. BTDT. Got to see a Volvo B20 exhaust manifold glow cherry red as a result.

Cold air out of the heater? You say that like it's a bad thing... but I agree it's not normal. The air coming out should be scalding hot, regardless of the control setting. Check the heater core hasn't been bypassed - often done on British cars in the US that don't often see cold weather use anyway. A second shut-off valve is common as well, although both of these are somewhat obvious if you've been fiddling with the car as much as you have.

The heater core certainly looks like it isn't bypassed, only one valve.

I drove it a couple miles last night and it ran great, no overheating. I checked the timing the timing this morning with a light and it was around 12deg BTDC, I backed it back down to 8 then went for a drive and it started overheating quite a bit. I advanced the timing a bit by ear (turned the distributer till the revs stopped rising and backed it off till they dropped slightly.

After that is was running better but still overheating unless I was just cruising with very little throttle.

The heater hose to the core off the heater valve isn't hot to the touch but it is open, when I squeeze it the coolant in the radiator bubbles. Maybe pointing to the coolant not circulating as it should.

Just ran it for a bit with the cap off to see if I could burp out and more air bubbles. The upper hose got hot but the coolant never bubbled over. The hose off the heater valve gets warm/hot but the return is cold.

Ran it a little longer and confirmed the coolant is circulating. I now have heat out of the heater. Still running hot, the gauge fluctuates quite a bit. Wondering if it could just be a bad sending unit since it drops extremely quickly when I am moving and shift into 4th gear, it goes from hot to normal (nearly half the gauge) in a second or two.

You need one of these (with real numbers) :

In reply to EvanB:

Also check the voltage regulator for the guages.

In reply to cghstang:

Yea, no kidding. For both of my cars.

I ordered a new temp sender so I will give that a shot.

Also the bearing(s) in the alternator are making quite a bit of racket. Anyone know if I could get a rebuild kit or will I have to buy a whole new one?

In reply to cghstang:

Have to make it look the part though.

I'd be shocked if you couldn't find bearings.

Found a rebuild kit in England.

http://www.ebay.com/itm/310201740368?item=310201740368&viewitem=&vxp=mtr

They list it as including this size of bearing:

http://www.grainger.com/Grainger/DAYTON-Radial-Ball-Bearing-1ZGH2?Pid=search

Although at $17.18 for two plus shipping I may as well just get a GM 1 wire to put in.

Put a new temperature sending unit in and it still is creeping up on the gauge. It drops back down at idle but under acceleration it goes up.

EvanB wrote: Put a new temperature sending unit in and it still is creeping up on the gauge. It drops back down at idle but under acceleration it goes up.

Did you check the voltage regulator? Smiths gauges like 10V. No more. No less. It sounds like the varying voltage coming off the alternator as the RPM goes up is affecting the gauge.

It's usually a little rectangular relay-looking thing on the back of the dash.

Interesting, I'll have to check.

Looking at a Mini wiring diagram, its called a voltage stabilizer and appears to be mounted on the back of the speedometer. It provides power to the temp gauge and fuel gauge.

I have noticed that the fuel gauge is a little inaccurate. It goes from 3/4 to full sometimes. I'll have to check it out tomorrow.