Max Gent

A couple of months ago (back in November actually) I purchased 1987 Audi 4000CS Quattro in Seattle from couple that claimed it was there baby and had always maintained it properly and it was currently their car they took to the mountain when I bought it. They had a reasonable amount of paper work from themselves and the previous owner but the one thing I was skeptical about is that they said it had an engine swap with an NF motor but there was no paper work for it and to be honest I don't exactly know how to tell if it is an NF or a JT but it did come with an external oil cooler. I drove the vehicle all the way back from Seattle back to my home in Oregon, about a 3 hour drive and it ran fine the whole way but when I started driving around in stop/go city traffic I started to notice something.

The temperature gauge would rise above normal and the fan would come on. After this started happening every time I drove it I decided to change the coolant , replace the thermostat, replace the coolant tank cap (which was cracked) and had a mechanic replace the timing belt and the water pump. I thought all would be better but its not the temperature gauge on the dashboard seemingly regardless of the temperature outside will rise and the fan will come on. I drove it when it had snowed and currently when its 80+ out the gauge goes up regardless while idling and the fan will come on and its a rather noisy fan. The most annoying part of the situation is when driving down the road the temperature appears to be fine and the temperature gauge will go down saying its running cold even.

Another issue I've had is that the heater only blows out of the drivers side, passenger side vents, and the defrost vent. The middle vent only blows cold air. The heat was never the strongest so a possibility I was thinking was the heater core but that does not tell me why the middle vent only blows cold air.

Those are the main problems with the vehicle currently and any help would be much appreciated. I'm a big fan of this car and was planning on daily driving it but do not want to risk any damage to it resulting from cooling problems. If more details are needed I would be happy to provide them to the best of my abilities. Please let me know if I'm missing anything important regarding the issues.

Thanks ahead of time,
Max--

Rogviler

That actually sounds pretty normal. Just how hot does it get on the gauge?

The center vent only lets fresh air in. Some people hate that, I've always liked it. But that's the way it was designed.

If you take a pic of the engine, I (or anyone on here) can tell you if it's an NF or JT. There also should be the code on the driver side of the block right where it meets the head kind of in the middle. That would tell you for sure.

-Rog

Joeltron

My 4000 ran really hot until I replaced the radiator, but I also replaced the thermostat and water pump at that time too. I also removed the AC but I don't think that made much difference. But now my car almost runs too cool. I can sit in bumper to bumper traffic on a 90 degree day and the needle barely get's half way up.

One thing to rule out is that the polarity of the fan hasn't been switched. I had this problem once in a 5000 I bought. It was running really hot, the fan was working its butt off, but come to find out, it was blowing air in from the back instead of sucking it in from the front. The previous owner had installed an inline fuse on the fan motor but had reversed the polarity in the process. I switched it back and it ran way cooler after that. Just a thought.

Yeah, that thing about the vents affects a lot of these cars. My hot/cool slider doesn't do a thing. I just close the driver and passenger vent, the defrost, and the floor vents when it's hot out, and open them when it's cold. Kind of annoying but I've learned to live with it.

Nice looking car. I'm jealous of those headlights! You just can't find 'em anymore (without spending $1,000)

TEF1701

Nice looking car, from one Northwesterner to another (I'm in Spokane). Ditto on the fresh air vent. I had to actually take my whole heater assembly out to realize they were designed that way. Of course I was replacing my heater core and cables anyway. I hated it at first, but I quickly realized how nice it was to crack it open a bit during the winter to let in some fresh air.

Regarding the temp gauge, you may want to check the temp sensor on the bottom of the thermostat housing just to make sure it's not causing false readings. The top one goes to your ECU, bottom one to your gauge. Since the fan keeps coming on, I would say it's probably fine. The only thing I have ever seen that would cause temperature fluctuations like that is air in the system. It doesn't take much of a leak to create air bubbles in the system. I would check all of your radiator hoses, heater hoses, and thermostat housing gasket. Also visually inspect the thermostat housing for hairline cracks. Air pockets will cause all sorts of fun inside a sealed cooling system.

Max Gent

Hello everyone, Sorry it's taken so long for me to get back to this I've been rather busy these past couple of weeks.

Well the gauge generally stays in the middle during most conditions while driving and idling if not for more then a couple of minutes. If I am idling for a prolonged amount of time say in traffic the gauge will rise a little bit to the next notch. then the noisy fan comes on for
a couple of minutes and then the gauge goes back down only to seemingly repeat the process.

I have checked the fan and it is indeed pulling air through the radiator from the front. I'm currently planning on replacing the radiator and flushing the entire coolant system out and replacing the coolant with G11. Or is the standard green coolant we use over here fine to use in these old cars? I've heard conflicting opinions and know the mixing the two causes a terrible brown sludge.

I have not had the time to do this yet but I plan to check it out and replace old hoses anyway while I'm doing other things. The thermostat and housing gasket should be in good order seeing as I replaced them recently but I'll give em a look as well as giving the thermostat housing a closer look.

I appreciate the speedy responses even though I move at the speed of a dying emu.

Had no idea they were that hard to find, I thought they were clear stock headlights until I tried to stick the us spec oem bulb size in and it was an H4. Along with some shoddy installation work from the previous owner.

Never knew the center vent was a fresh air vent but its been nice when its warm out because the other vents inexplicably blow hot air even when the **** is at zero.

Rogviler

Yeah, that sounds perfectly normal to me as far as the temperature and fan behavior.

-Rog

flailhyena

Ditto.

The fan has to come on when the car is stopped otherwise there is no airflow for the radiator to do it's job.

As for the debate over G11 or regular green stuff, so long as your coolant isn't dark brown, stick with whatever is currently in there. Don't try to flush and switch to one or the other because odds are you won't get it all out and they will mix. I have had the green stuff in my VW fox since I bought the car 7 years ago with no problems. When I bought my Audi 90 the guy had mixed the two. I took all the hoses off and flushed them, and flushed the radiator and engine countless times and put in G11. My coolant is still brown.

In any case, in the right circles the G11 vs Green debate can stir up quite an argument, so I won't say anything more. Google the debate if you want, but I guarantee you that you will only wind up more torn on the decision.

Rogviler

If you want to switch to a more proper coolant without going nuts, go with G05. You can get it at Napa and it's pretty cheap. It's a long-life coolant, unlike the green stuff which is the main problem with it. Most people never change their coolant so it breaks down and that's where the "green stuff sucks"..."I've been using it since 1933 and it's fine!" debate usually comes from...

If you flush the system, don't forget to turn the heater on so it flushes the core. Also, it's pretty easy to get everything out if you just run a garden hose into the coolant tank with the bottom radiator hose off. You'll also want to break an old thermostat so it stays open. Once it's running clear, then use a standard coolant flush, then you can do a run with just distilled water. Should be pretty clean by then, certainly enough for G05.

Either way, it won't change how hot or cool it runs.

-Rog

flailhyena

Now that you mention it I can't remember if I did or not... Derp!