Neat method for limping an overheating car

As some of you know, I drive a Quantum. VW shoved the radiator so far off to the side that it's actually behind the alternator, so it kinda requires having a fan to cool the engine, even at highway speeds.

I've been dealing with overheating issues. First the thermostat exploded. Then, last night it was overheating again, took time off work this morning to diagnose insufficient power getting to the fan switch. I'd get power but under load there was nothing. Somebody replaced an underhood junction connector with a SCOTCH-LOCK and this of course resulted in much green death. Repaired that properly, now I can power the fan by jumpering the switch, but gotta clock in and get cars repaired and make money, but it's fixed now right? Right?

Of course, this wasn't the only problem, and it was overheating again after work, problem manifesting far from home. What to do?

Modern cars have all sorts of neat heat-management algorithms in the software. For example, at critical temps (usually 260F) they cut one bank of cylinders and cool the engine with air, switching banks every so often. Maybe 40hjp at WOT but you're not stranded and not killing the engine.

This is not an option when you have a distributor and Bosch K-jet that probably has vacuum tubes in its control box. BUT! We can improvise.

Limp car up hill, eyes solidly locked on temp gauge. Crest hill at decent clip - 70-75mph in this case. When you start going downhill, shut engine off, leave in gear, and mat the throttle. (Helps if the engine has the compression of an old lawnmower with the easy-start governor stuck on) The engine gets lots of air, cooling it from the inside, the water pump will still be circulating coolant to the radiator, and the coolant is moving without added heat from combustion.

5-10 seconds of coasting is worth about 25-30 degrees drop in coolant temp.

Limped it all the way home this way. Never pegged the gauge.

Huh. I don't understand half the things you just said, but I sure do like scotch. If scotch lock is anything like life-lock, sign me up.

When I put my Hyundai Tiburon into a ditch to avoid Tboning a minivan in the rain.. I ripped the bottom of the radiator out 20 miles from home (and nobody stopped to help)

After getting the car out of the ditch, I ran her home by getting her above the speed limit.. say 10 over.. and shutting down and letting her coast down to 10 under.. restart by putting in 5th and letting the clutch out... lather, rinse, repeat. Temps started to get hot by the time I got home.. but I got home

I understood it. Nice trick but don't try it on a carbed engine for sure

Another one which we all should already know is to drop the windows and crank the heat, using the heater core as a mini-radiator.

I believe Cadillac had a similar system with the northstar V8, it would only fire the injectors every other intake stroke or something like that if overheated.

GameboyRMH wrote: I understood it. Nice trick but don't try it on a carbed engine for sure

Troof!!!

In all honesty, I think by having the throttle body open, you are increasing the surface area for heat to transfer to the air while having a huge heat pump to move the air around. Of course this in addition to the water pump still circulating allowing the normal water to air cooling.

Very clever sir!

Edit: I have experience with MK2 VWs and jumping the cooling switch as well as owning a Fox wagon, so I know your pain.

That is a really good idea I need to remember that one.

My 87 Scirocco decided to let the water pump die in NC as I was going home to DE. I struggled and had no hills to utilize. Pulled the t-stat on the side of the road.

1. Pulling a t-stat on a reverse flow engine is no fun. Less so when you're doing it on wet gravel in a ditch hoping no one will notice as they pass you.

2. That trick would have been near impossible if I had not removed the power steering a couple weeks earlier.

It ran home cold as an ex-wife's heart, but it ran me home.

That reminds me of the flathead Caddy that came to us overheating when driving down the road, but ran cool as a cucumber sitting there idling.

Two notes:

The radiator sat a lot higher than the engine

No thermostat as we know it. There was a thermostatically controlled set of Venetian blinds in front of the radiator. Everything old is new again...

Long story short, the water pump that he'd had somebody rebuild for him had the impeller fall off. Engine cooling was entirely by thermosiphon: Hot water rose in the engine, up to the radiator, where it would cool off and sink. Some old motorcycle engines used this exclusively for water flow, but this isn't quite enough for a '41 Cad.

lost the belt on the wife's cavalier on the turnpike at 9:30 once, 5 miles from the exit that i knew an autozone was 10 minutes from. i would get up to 80 and toss in neutral/shut it down and coast. drop down to 40, fire it up and do the same thing. i coasted the whole exit ramp and luckily the road to the store was 50mph so i got up to 60 and would shut it down to 20 because at that time it was getting pretty warm.

coasted to the store at 9:55, they close at 10. bought a belt and found a bad pulley, they let me back in to get the pulley and a cheap flashlight. fixed it in the parking lot and drove home.

also, turn the heater on full blast. heater core acts like mini radiator.

My Mini cools best at WOT. Can't explain it, but it sure makes it more fun to drive.

I thermosiphoned an old Datsun 510 across the top of Pennsylvania once, many years ago, when the fan belt snapped. That was back when gas stations frequently weren't open on Sundays, let alone car parts stores.

It actually worked quite well.

It works on carbed VWs too. Don't need to turn it off and floor it though, just back off the gas. A buddy had a cylinder head temp guage in his bus and the temp drop was impressive.

I used to have a customer with an old Clark forklift that a continental flat head six. I would get atleast two service calls a year for it overheating. It had a bad WP, I suspect that the impeller was loose on the shaft or the vanes had rusted away from old age, for reasons unknown, they would not let me replace it. Anyway, the radiator was high above the engine so as long as they were not running it hard, it would circulate coolant through convection. I really hated that machine.

If the temperature switch doesn't work (I own a VW, so I understand) I usually try putting the defroster on because that will engage the AC. Normally the radiator fan will come on with the AC, even with a dead temperature switch.

That'd work if the A/C system hadn't been hacked out. But I used to do that, too.

On one of my Mazdas, I used the A/C switch to turn the electric fan off and on.

Kenny_McCormic wrote: I believe Cadillac had a similar system with the northstar V8, it would only fire the injectors every other intake stroke or something like that if overheated.

You could say that it was the first car to do that.

Lots and lots of other cars have it now- it was very much developed as more and more aluminum found it's way into truck engines. One could drive and not damage a full iron engine without coolant, but an aluminum head would warp. So by doing this method, as the OP states, you have a way to limp someplace when the cooling system fails.

Keith Tanner wrote: My Mini cools best at WOT. Can't explain it, but it sure makes it more fun to drive.

We call that C.R.A.P.

And I'm not kidding. BMW/Bosch isn't the only one who found that nice secret. Some of us are not all that pleased with it, though. Basically, it runs richer- the extra fuel cools combustion temps by quite a bit, and that helps keep the engine from getting too hot.

Great idea there!

had a friends 72 Barracuda lose a freeze plug too many miles from home and limped it in. Drove her till she went up to about 3/4s hot and pull over and shut it off for about 45 minutes. repeat until home...