Cooling system diagnosint - Water pump?

[dusred]

I don't drive the Q very much but a while back it started heating up above the desirable temperature and I found out that the radiator was leaking and the Q was low on water. So I replaced the Radiator and the car was still heating up so I added an AUX trans cooler and it was still doing it. I then replaced the fan clutch and the Thermostat and it is still heating up.

Whats left? The only thing that I can think of is the water pump. How can I tell for sure if it is the water pump?

Thanks

[maxnix]

OEM or mystery 3rd party sourced parts?

Critical for thermostat, tank tops and water pump.

[jimbyjimb]

When the car is cold loosen the radiator cap, do not remove, loosen. Start the car and wait for it to reach peak temp and then remove cap. If the pump is functioning you should be able to see circulation in the radiator. It's a simplistic test but works 9/10 times in my experience in pump functionality determination. If you need more clarity feel free to Email.

[Q45tech]

Pumps never fail: they leak from weep hole, make noise from bad seals and bearings, or reduce flow from acid eaten impellers.

Since head gasket failure is extremely rare unless the engine has been overheated. You always check coolant for hydrocarbon gases [use the typical device] and measure pressure build up time and ramp up rate. To confirm.

Using aftermarket parts which are only 95-90% as efficient to new oem may reduce the safety spread.

Really difficult to diagnose without accurate temperature number and a time to rise chart, idle rpm, ambient temperature, ac on/off.

Many times overheats are somethings you forget like the rubber air surround around radiater allowing an air feedback fom engine compartment to the input side of rad. A restricted airflow condenser, dead auxillary electric fan in front of condenser. high idle rpm, more than 50% AF in coolant.

[dusred]

Is there a way to test the AUX fan?

[maxnix]

Is there a way to test the AUX fan?

Just observe it.

It would also help us to help you if you would answer the questions asked.

[dusred]

Okay, I haven't driven the Q for a few months since I made this thread but the problem still exists so I want to figure it out.

To answer your questions, Tech, the water pump doesn't leak from the weep hole or make strange noises.

The car has been heated up but I have never let it get past the safe zone on the engine temp gauge.

What's the typical device you use to check for hydrocarbon gases?

I have only used OEM parts on my car.

What is this "rubber air surround" you speak of?

I just cleaned the air condenser so that shouldn't be a problem. I was suspecting the AUX fan because it didn't seem to be blowing as hard as it should be.

I really appreciate the help, Tech, and others on here.

[Infinitiguy19]

I think he mean a coolant pressure tester (Available at Auto zone for rent for $75).

[maxnix]

The car has been heated up but I have never let it get past the safe zone on the engine temp gauge.

The lag in the temperature gauge is so great there is no guarantee the engine's temperature did not transgress into the fatal zone. Further more, once the senor has no liquid surrounding it, the actual coolant termperature is unknown to it, so the engine will be overheating in at least that location, but the gauge won't indicate it.

Aluminum has little tolerance for over heating.
Modified by maxnix at 7:38 PM 10/10/2008

[dusred]

Okay,

Lets say it did "overheat" how can I tell what damage was done? And if it did do damage to the engine/head gasket how can that effect the cooling system?

[Q45tech]

Assumming an overheat, a blown warped head and gasket will alow combustion gases into coolant, raising the pressure, which can be read on a coolant system pressure gauge. The Combustion gases [hydrocarbons] bubbles can be analysed with the hydrocarbon/gas test tool.

The point is tools are necessary along with technical education to use them. At least the ability to follow written instructions precisely.

[fixer]

I have had aftermarket radiator cause your kind of problem on a Q45 from utah. I live in Las Vegas and the summertime temps get pretty high. I got a Q fronm utah that complained of overheating and raditaor and thermostat was replaced, there was no coolant leaks, I tested with a pressure tester. and the head gasket was fine, I tested with a block tester. what I found was an aftermarket radiator installed. I recognized the afterrmarket radiator because the markings were different and the shape of the top tank was a little different. maybe to the untrained eye the radiator would look like a factory radiator. If you installed a used factory replacement, you may have a partially clogged radiator. It will need to be flushed by a radiator shop. about the block tester, it is a tube that fits on the opening of the radfiator for the cap, and has a bladder on top to suck gasses from the radiator. you fill with block tester fluid that changes color if exhaust gasses are present. the cost of the tool is minimal and the fluid isnt much either. you can purcahse from any tool distributor. you may have trouble finding it at pep boys or auto zone

[Unnatural1]

NAPA sells block tester kits.

When does it get hot? Will it sit at idle and overheat or only overheat while driving/cruising?

If you have access to a laser thermometer use it to take some temp readings of the radiator at a couple of points; top, bottom, and each side. There will be some temperature variation but not like a 100*F difference.

[dix]

I have an overheating problem I'm trying to diagnose. I'll be driving along in warm weather and the temp gauge begins to rise quite quickly. I find that if I rev the engine either as I'm going along or at a stop, in neutral, I can get the the gauge to come back down from one of the high marks to the mid point also pretty quickly..much more quickly than it would seem to for the coolant temperature actually change that much. Does this point to anything in particular.

[Q45tech]

Impossible to diagnose over inet without a series of ACCURATE [ +-1.0F] data points as to rad input and output temperature vs engine rpm vs speed.

Since a rad may only drop temp 10-15F from input to output.

Almost always the problems are a used old, dirty, bent fin radiator especially after 8 years [depending on mileage].

After market rads while they fit are made of thinner plastic and aluminum, their fin count per inch is less and generally under stress thay perform 10% less than new OEM.

While 10% less may not sound like much adegree here and there soon adds up causing the feedback system [thermostat vs pump] to lose control with a slow steady rise in coolant temperature.

Why it is important to create a graph of coolant vs ambient vs time in 15 second increments from a cold crank for 15 minutes [60 data points] idling in shade.

THEN turn AC on MAX and data log for another 10 minutes.

DO IT AND YOU WILL SEE what I am saying.

Unfortunately you need a CONSULT to see coolant temp as ecu sees coolant temp.

I drive non engineering techs battey with all my engineering data recovery.

BUT THE DATA NEVER LIES!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

The GREGORY HOUSE of Automotive Technology

AFTER ALL if you combust X amount of gasoline in Y time at Z efficiency an exact amount of HEAT is generated. The heat can only go 3 places sitting still..Heat the air underhood, heat the coolamt, or flow out exhaust pipe

[dix]

Unfortunately collecting the data you describe is not possible for me. Is the field of possible problems narrowed down by the fact that a few good revs of the engine will bring the temp gauge back down quickly?

Thanks