Radiator volume?

In the USA the first year for the passat was 1990. That said just buy 1 gal coolant and mix 50/50%.

Thanks Lost but I've got a problem with overheating. Trying to find out if it's the engine or rad. Cheers

RD

My 84 required burping. Some folks drill a small hole in the thermostat to allow a little air/water to bypass which can help burp faster. I think on some VW engines there is a burp port. Not on the one in your engine. Coolant capacity can be an interesting number but sometimes not so useful. Usually there is coolant left in the heater core and the block. If you have a half gallon left then knowing it can hold 2 gallons does not help.

I filled up the system the normal way with the top radiator hose loose. I then tried to add more coolant to that loose hose. Put it all together and top off some more. Leaving the cap off the reservoir I start the engine and set the car heat to high. After idling a bit hopefully you have enough coolant that it surrounds the thermostat and opens it up. You should have some bubbles escaping from the reservoir. Ideally the top radiator hose gets hot suggesting that the thermostat has opened up.

My Rabbit service manual does not have a coolant capacity listed. Maybe VW did not publish that fact.

Thanks Jim. Useful tips. Cheers.

RD

Jim Behn>My 84 required burping. Some folks drill a small hole in the

Hi Lost. It's an 1800cc 4cyl. The temp gauge in normal use is almost to the top of the scale but not quite high enough to light the warning lamp. I've had the car from new. Initially the pointer on the temp gauge was about a quarter inch from the bottom of the scale when fully warmed up. Over the last two years it's gone to a quarter inch from the top of the scale, almost on the red. The pump definitely is working Ok, I checked. I've replaced the thermostat with two new ones, the last one being a VW genuine part just in case. So I figure it's either the engine galleries clogging up or the rad. Someone here suggested measuring the amount of water in the rad against what it should be as the best place to start. That's where I am today. Thanks

RD

Lost >what engine? what are the symptoms and what have you checked and what are >the results?

I'd suggest first determining whether it is *really* overheating, or just that the gauge is inaccurate.

Get a good, calibrated, IR thermometer and get it up to temperature. Then shoot the temps of the upper and lower radiator hoses. Also shoot the radiator tanks as well, and for good measure the engine block in a couple of places. (IR temp gauges are fun, you'll see!)

Then post the numbers you get...

I agree with PeterD!

How long does it take to heat up? Does the cooling system instantly pressurize when you start the engine? Does the radiator fan come on and when? It should have 2 speeds and your rad fan switch may be defective, or the wiring to it. AND does it blow hot air when the fan does come on? Is the radiator getting hot in all four corners? I have seen some that were clogged at the bottom. Did you try running it without a thermostat ever? Ever flushed out the radiator? New temperature sending unit for the gauge?

Dave thanks. It heats up very quickly. The fan comes almost as soon as I spend any time in heavy traffic with the engine either idling or in low gear. Before it would take about twenty minutes in those conditions for it to come on. Yes I've flushed the rad twice with a cleaner and the water now runs clear.

dave AKA vwdoc1 wrote:

Harbor Freight, less than $10 (plus S&H of course).

I have read that on certain engines running without a thermostat can cause overheating. Maybe the water moves too fast to pickup heat. Or maybe it bubbles when moving too fast. Maybe it is an urban myth.

Then I would suspect a clogged/bad radiator. :-(

Not myth, true. I've seen it happen. Best reason that we came up with was the water moving too fast one.

Well in the summer where I live my 84 would turn on the fan fairly quickly on hot days. Is it 90F where you live right now or 20F? Or -5C or 30C? I don't believe that on a warm day stuck in traffic that the radiator fan would take 20 minutes before it would turn on unless it was a diesel which runs cooler than a gas engine. It certainly came on faster than that on my Rabbits. In fact I have had the fan cut on a warm day after just two minutes. I know this as I was trying to get home when my car had a bad alternator. I got stuck at a traffic light a mile from home. The radiator fan kicked in and the engine died due to low voltage at the coil.

Water flowing clean out of a radiator does not mean that there are not blocked tubes.

Have you replaced the water pump with one with a metal impeller? Have you replaced the water pump without comparing the old to the new? I thought I had read that some pumps have an impeller smaller than others. If it is the wrong size then it will no pump properly. I have also read that sometimes plastic impellers will get loose and spin on the shaft. But that would not explain a fan turning on soon as a pump that does not pump is not going to trigger radiator fan switch located in the radiator.

Have you backwashed the raditor and block? High volume of water flow>Then I would suspect a clogged/bad radiator. :-(