Overheating issue.... Cant figure this one out

[cmartinez]

Hello all, I've looked throughout the threads and various resources online and have no idea on where to go to get an answer. You guys seem the most knowledgeable and I have been able to pick up many pointers from audiworld so I figure this would be my best bet at finding an answer. Here is my detailed situation.

Bought a used 2001 A4 1.8t FWD. Looks like the previous owner had made a few mods to it and now, I guess I am left in the dark to figuring out why the car is overheating. Here is what I have checked and what I have done, hopefully someone can tell me what I need to do or what I did to make this happen.


Heres what happens:

Got the car about a week ago, have since put about 200 miles on it, was fine at first but now it seems as though at idle the car overheats, it goes over the midway point on the gage when I am moving, but just barely over the line. The ram air seems to keep the engine cool enough when moving and it's not like the temp spikes up in seconds but a few minutes at a light makes the temp go up a notch.

Both fans kick on when they are supposed to (so i assume it's not the t-stat), coolant levels are fine with no leaks in the tank or hoses, ac comes out cold...

Could it be my water pump? Is there a way to check that out without ripping the frontend off and getting into the nitty gritty?


Here's whats been done:

Seems like the previous owner had a manual turbo controller setup, cant really tell what the setting is at as I haven't set it up with a boost gage or taken it to get checked, could this be doing it? Also, I had put in the lucas gas treatment stuff as the mechanic that I talked to recommended since it was sitting for a couple months before I got it, could this be doing it? Also, I bought some of the Advance Auto Coolant 50/50 and put in as the coolant levels were low.... could this be doing it?
Also, it has an intake system that looks to be a K&M, I replaced the filter on it for a new cone filter and replaced the other filter (not sure what it was, but it was right next to the intake filter) as the old ones were really dirty. I did replace them with the right size filters, identical to the ones it had in. Could the filter change be causing the overheat?

I have gotten some really strong suggestions to include coolant, thermostat and water pump. I feel as though the fans turning on cancel out the thermostat, the coolant (as long as what i used isnt bad) shouldn't be the issue because there is no leaks and although it goes down a very very small amount it doesnt go down fast enough for the car to overheat before i notice it.

It seems the engine gets really hot, even just by standing in front of the hood, even for a turbo. Can it be that the turbo boost is set to a psi that is too high? If so, what is the recommended level?

Any suggestions or recommendations greatly appreciated and welcomed.

Also, I can take pictures if need be.

 

[Broken Byzan]

Waterpump is a common failiure if it has not done before. How many miles has she done?

Has the coolant in the header tank turned to a jelly substance? As the VAG group use G12 Plus pink coolant and it really doesnt mix with anything else TBH

 

[cmartinez]

Thanks for the reply mark

The car has an 133,xxx miles on it, i ran a carfax and it looks like up until 111,xxx miles it had all it's servicing done as recommended by mechanic. Only thing is that the records dont state whether the pump, tbelt or t-stat have been changed (obviously). Is there anyway to check whether the pump is bad or not without having to dismount the whole front end?

It doesnt look like the coolant has turned to jelly or anything, there is some residue inside of the resevoir container (rust colored kind of) but I think it is just because it was sitting there with almost no coolant in it (about half way to minimum level marker on resevoir). Would you recommend to flush the coolant and replace with G12?

 

[Broken Byzan]

To be honest at 133k it's due a belt soon anyway, so whip that front end off and change the waterpump, Stat and timing belt and tensioners, she will be like a new car then.

The problem is the water pump breaks up inside so you cannot see it without removing the pump from the car. The impellar is made of plastic and gets brittle with age and then seperates from the spindle/splines and therefor is no longer driven.

I would deffo flush it, i don't suppose it would hurt to try , I could be completly wrong, however my actual cash would be on the pump tbh

 

[Siena]

Water pump issues manifest the other way round - overheating at speed, and cooling when at idle or slow speeds.

The plastic impeller cracks, so at slow speeds, the impeller matches the shaft speed, and pushes coolant round the engine. However, at higher engine rpm, the shaft spins faster than the impeller, which sometimes stalls, so of course, the coolant becomes static, causing over heating issues.

As yours is over heating at idle, but cooler at higher rpm, whereby the ram effect is supplying enough air to keep temps down, I'd suspect the thermostat or fans. I'd check the blades, and make sure none are broken. Thermo switch should be checked too, to ensure it engages the fan/s at the right time, and not when the coolant is boiling.

You can VAG the system, get more insight.

 

[docurley]

I would have to agree with Siena as thats what happend to mine your sound like what Siena is saying but I would also replace the temp sensor while your at it.

 

[Matt82]

id place a bet on the expansion tank cap too. see if you can find out about the water pump

if you wanted to go nuts id start with dumping the coolant, putting a new stat in. new fan switch on the rad and a new expansion tank.

check to see if the small hose that returns to the expansion tank is not blocked too. that has given me some odd overheating problems in the pass

 

[aragorn]

Just because the cooling fans run doesnt mean the thermostat is working, they're entirely seperate systems.

Thermostat controls the flow of water thru the radiator. Rad fan switch monitors the radiator temperature and if it exceeds a set point turns the fans on.

The other point is the coolant temp guage should sit at 90 at all normal operating conditions. The dash has a buffer built in such that it reads "90" at any temp between something like 75 and 105. If its moving up past 90, then the temp is quite a bit over the "normal" range.

On the coolant, G12+ is fine to mix with the green stuff (G11), The original G12 isnt.