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Discussion Starter · #1 ·
Hey all, looking for any advice on my issues here. I've got an 81 diesel caddy. Currently overheating and I'm not sure where to look next. It's always done fine, even when I lived in Arizona (I'm in SE Ohio now). Last summer on a trip to Pittsburg it started overheating climbing all the hills in West Virginia. I had just replaced the timing belt that winter and had been putting off doing the water pump, and had seen no signs of head gasket failure (no oil in coolant or vise versa). Replaced the water pump with a part I got from a friend that looked new, labels made in Germany, looked like a newer appropriate pump, and a new thermostat. I tested the thermostat in water and it opened @180f .the pump has one of those weeping holes and immediately I saw coolant leek out of there. Also since doing this my running temperature is up a few ticks from where it used to be, though it didn't overheat and tended to stay in the middle of the temp gauge. Well, it's overheating again and I just don't know if I should replace the pump again? Is a leak in the pump a definite failure? Seems odd it was brand new but maybe it was defective. I'm other questions are just where else to look. As I said I haven't notice anything bad about the head gasket and I replaced the radiator about 5 yrs ago with a cheap one. Can I test it's performance? Coolabt system was flushed by running a hose in through the resevoir when i installed the new pump. Also, it does run a notch or so cooler when I run through the heater core if that is helpful. Thanks!
 

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If the water pump is leaking out the weep hole there is a coolant leak at the front seal, REPLACE IT, flush and back flush your cooling system.

Don't guess about head gaskets do the Glove test to rule it out.
When the car is running with a leak then the head gasket can fail and you won't see the hoses balloon as the pressure is being relieved by the leak at the seal.

Change the pump, flush back flush then the glove test.
 

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If the water pump is leaking out the weep hole there is a coolant leak at the front seal, REPLACE IT, flush and back flush your cooling system.

Don't guess about head gaskets do the Glove test to rule it out.
When the car is running with a leak then the head gasket can fail and you won't see the hoses balloon as the pressure is being relieved by the leak at the seal.

Change the pump, flush back flush then the glove test.
What is a glove test?
 

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Engine Cold.
open the expansion tank.
tie Latex Glove over the expansion tank hole tightly.
Start car.
Quickly from under the hood raise the RPM to 3000 for 30-45 seconds if the glove inflates bad head gasket after 45 seconds the gole will start to inflate normally...

If you are running the engine and it is up to temp, do your water hoses expand and are Ballooned and hard to Squeeze, Bad head Gasket.
If you have a oily ring in the expansion tank, Bad Head Gasket.
If you are leaking oil out between the 3rd and 4th cylinder in the front, yep Bad Head Gasket.

On gassers with the water cooled oil cooler on the oil filter flange, this could also be a sign that it is a bad oil cooler and that is a whole lot easier to change out first to eliminate the possibility of a bad head gasket or bad oil cooler.
 

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Discussion Starter · #5 ·
Thanks, I'm glad you posted this cause I did the glove test but not starting cold. I searched through the forums and found references to it but didn't see a defined how to. I'll try this later. Strangely the water pump doesn't seem to be leaking at the moment but the head gasket area is moist at various points. Seems the more specific problem is if I get hot from climbing(doesn't happen in traffic though we don't have much around here) it doesn't cool back down until i stop driving or hit some serious downhilss
 

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Make sure that your radiator fan switch is working and that the fan relay and fuse are good to go. Then address the issue of the separate ground wire to the fan motor, as the Fan is using an isolated ground unlike a lot of American cars, the fan shroud isn't grounded as it is into plastic on most models and that is why it is imperative that your ground is good to the motor.

If you jumper 12V+ to the motor and ground from the battery, it should spin..... If it is a 2 speed fan do both red/white wires to ground separately and you should see two distinct speeds.

The Radiator Fan switch is the heart of the relay system as it turns the relay on or off. See Chris's wiring to understand it IIRC it starts at page 72 of section 1.

Moisture around the head well using a UV light check all hoses and flanges, as if an o-ring holes or flattens out you can get a fine mist of spray that is hard to see, I had a WP do that on my Van until it finally gave up when I was out of town, and had to change it out...

The old Green Prestone type of coolant shines up under UV and the UV light as well as a pressure tester for cold engines and the Expansion system is another tool to have in your chest for a rainy day as you may use it once or twice in ten years, but it does make short work of diagnosis.

Now I will tell you from past experiences with a diesel on a hill they do tend to get overly hot on the climbs but it seems that the fan will keep the temps moderated....but I have seen it climb almost to the hot mark, but I too noticed that on the down hill it cools rather quickly, and if you get behind a car on the climb it interrupts the forced air over the radiator making it work harder...

In 300+Kmiles of ownership I only went through 1 water pump.... and it wasn't unusual for the Car to do a 1500 mile week end trip. The Best thing that ever happened to me was the fact that at 20114 miles the oem radiator split the core from the Tank because of the stupid Clip mount and bolting fast to the frame at the bottom allowing it to vibrate and torsion shear...That issue was resolved with the purchase of a Brass and Copper Radiator that for the next 19 years of ownership and a few bad head gaskets never failed on me at all.

On my current Cabriolet I have had to buy a new radiator, and opted for the totally Aluminum one as a replacement, even though they hard mount at the top and bottom on a Cabby, which I suggest that it should be done on the golf/rabbit I have noticed that it cools things better. Yes I bought the plastic and aluminum one after about 2 months of ownership 12-to-15 years ago I opted for a better version. I did have to grind off the fan mounts on the front of it so the radiator wouldn't touch my condenser.... when that goes again I will change it out for a parallel flow type that the newer cars use as it is more efficient than the circle the wagons one we currently use for the r12 systems of old...
 

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Discussion Starter · #7 ·
The radiator fan definitely works as it's is usually running when I get where I'm going if the outside temp is over 80f. The glove test gave me a negative result but I have been noticing an exhaust smell that's been getting stronger and though I don't see oil in my coolant, it looks murky or exhausty. Seems though if I Where getting exhaust in my coolant the glove test would be positive so I will try again.
 

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Exhaust smell, it usually isn't the exhaust that you contaminate the AF with.
May have an exhaust leak at the Bowl Joint, as the gaskets have been known to fail.
 

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The fan circuit in a MK1 cannot be trusted for long run times like climbing a mountain. Many fuse panels have that fuse (and near area) semi-melted from heat.
I tapped into the hot wire to the radiator fan and have a relay (direct from the battery with a fuse) operated with a manual switch in the cab. It actually makes the fan run a little faster than the factory wiring. Going up a grade I'll hit the switch and leave it on till the climb is done.

I also tap a smaller wire into the same main wire to the radiator fan and run to a small indicator light somewhere easily visible on the dash. Lets you know when the radiator fan is getting power while you're driving. It's kinda weird, but I want to know if that fan is getting power when it's supposed to. If it's not - I go to the manual switch, if that doesn't work, better pull over and have a look.
 
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