99 3.4 Overheating

[darrinsmith]

Hi

I got my 99 3.4 tiptronic cab out for a drive today, and it got really hot while driving.

It has been sitting for about 4 weeks, and was all fine before.

The coolant level is fine, fans are working, and there are no obvious coolant leaks or blockages in the radiators.

The car warms up normally, but if I stop at traffic lights etc, the temp creeps way up.

If I start driving the temp goes back down to close to normal, but is still much higher than normal.

A bit wierd really,

Where should I start troubleshooting, coolant cut off valve? Is there a way to check if the thermostat is stuck?

It is warm here at the moment, (in the high 30's celcius) but it's never run this hot before.

Thanks

DS

[Steve Tinker]

Darrin - if the temps are fine untill you hit traffic, the cooling fans should drop the temperatures to normal. If not, the radiators and the A/C condensers (mounted in front of them) could be blocked. You ca'nt see this from the front of the car - the blockage is caused by debris between the 2 radiators ( 2 each side of the car).

My Boxster S had so much c**** between the rads that it was running hot on a normally cool day. To access the rads, the front bumper must be removed. and the rads seperated.....

Hope this helps.

[Rapewta]

+ 1 on Steve Tinker's post.

My Carrera would get up to 200 deg f in slow traffic.

Both radiators were at least 20 percent blocked by years of (bought car used) collecting leaves and other

debris. Was pretty caked up. Cleaned and made a 10 degree difference. In my opinion,

190 degress plus or minus 10 degrees is optimum operating temp.

[fpb111]

4 weeks sitting? Maybe some varmints setup housekeeping in the radiator intakes.

How did you determine that the fans were working? It sounds like the low speed fan setting is not activating. Did you let the car warmup and listen for the fans to switch on? If you switch the AC on does the temp come down in traffic? AC switches the fans to high speed.

Edited February 1, 2011 by fpb111

[JeTexas]

My vote is that the fans aren't kicking on. The temp drop you see when moving is from movement of air caused by movement of the car.

[danhause]

I would agree the fans should be checked first to see if they are on when temp is rising at a stand still. If not I would check fuses and electrical connections first.

[darrinsmith]

Hi

Thanks fans are definately working, I triggered them with drive links on durametric to be sure.

The left hand fan is not moving much air, compared to the right, and I did have a problem with a resident rodent, so I'll pull off the bottom of the car and take a look this weekend.

I thought I had cleaned up all her mess!

Thanks!

DS

[darrinsmith]

Ok cleaned out the fans (10 years worth of crap!), got out about 2 kgs of sand!

Car is running much cooler, but still warmer than before.

Maybe thermostat is jammed? Is there an easy way to test apart from replacing it?

I have to make the 40km trip to the dealer this week anyway, so I can get one.

Fans appear to be working fine, coolant is only a few months old, and level is correct.

Thanks

DS

[c337cc]

Ok cleaned out the fans (10 years worth of crap!), got out about 2 kgs of sand!

Car is running much cooler, but still warmer than before.

Maybe thermostat is jammed? Is there an easy way to test apart from replacing it?

I have to make the 40km trip to the dealer this week anyway, so I can get one.

Fans appear to be working fine, coolant is only a few months old, and level is correct.

Thanks

DS

Just because you can activate the fans with durametrics doesn't mean they are working properly in real time. make sure the fans are running when the temps start climbing,and don't keep driving it with the temps high or you will crack a head.

Howard

[darrinsmith]

Hi

I have verified that both speeds of fan are operating with the engine running. I never have a reason to turn off the A/C so the low speed fans run whenever the engine is on.

They are moving lots of air now, verified by holding my hand over the inlet, and also under the nose of the car, where there is *lots* of hot air coming out, especially when the fans kick over into high speed.

It was a little warm here today 35oC (95oF) and the temp gauge on the dash was running at about 90-95oC (194-203oF) in very light stop-start traffic.

My other 996 (abeit a turbo but also a tiptronic) is rock solid on 80oC (176oF) in the same weather, even when driving with gusto.

Previously the car was also rock solid on about 85oC (185oF) in even on the hottest days.

It's all well within the vehicles tolerances, but I'm just trying to figure out why, even after cleaning the radiators, the car is all of a sudden running about 10oC hotter than usual.

Am I worried about nothing? I'm thinking I might change the thermostat anyhow, seeing as how I also have to do the oil pressure sender so it can be a great big rear-end off weekend!

I'm just trying to decide, as the dealer here does not keep any parts in stock (apart from basic service items, filters etc), everything is ex-melbourne which is a 2-3 day wait, and it is a 90km (about 55 miles) round trip to the dealer for me if I forget something.

Thanks

DS

[RFM]

Darrin, are you sure the cooling system pressure is correct? With a faulty cap the cooling system generates no or not enough pressure which results in higher engine temperatures.

[darrinsmith]

Good point,

I assume I could just swap the cap with my 2004 turbo to test?

It has a brand new cap.

Thanks

DS

[RFM]

Yes, you can give it a try to be sure, some next steps to take are damaged water pump rotor, thermostat, clogged radiator(s), etc.

[twcjcarrera]

4 weeks sitting? Maybe some varmints setup housekeeping in the radiator intakes.

How did you determine that the fans were working? It sounds like the low speed fan setting is not activating. Did you let the car warmup and listen for the fans to switch on? If you switch the AC on does the temp come down in traffic? AC switches the fans to high speed.

Interesting you say that because mine recently starts to creep up but only if the a/c is in the off mode but if i turn the a/c on then it brings it down. Where is the low speed fan or relay at?

[fpb111]

Someone more knowledgeable should chime in on this.

What you are seeing might be normal. With AC off the fans start at a lower speed until ~200 then switch to high speed.

If you have never removed the front bumper cover and cleaned in front of and between the AC condensers and radiators you should do that also.

The fans are two speed one fan on each side of the front of the car.

Most of he relays live above the fuse panel by your left foot if left side drive. Check the fuses also. There are ballast resisters in the fan assys that can burn out. Let the car reach operating temp and with AC OFF listen when the fans come on to make sure both are running.

Edited March 4, 2011 by fpb111

[1schoir]

4 weeks sitting? Maybe some varmints setup housekeeping in the radiator intakes.

How did you determine that the fans were working? It sounds like the low speed fan setting is not activating. Did you let the car warmup and listen for the fans to switch on? If you switch the AC on does the temp come down in traffic? AC switches the fans to high speed.

Interesting you say that because mine recently starts to creep up but only if the a/c is in the off mode but if i turn the a/c on then it brings it down. Where is the low speed fan or relay at?

twcj:

(Note that the following is from a 986 Boxster, but it should give you an idea of what you are dealing with).

There is one fan behind each radiator, and it runs at either a high speed or a low speed, depending on coolant temperature and/or whether the A/C is switched on or not.

The two speeds are achieved by means of relays, four of them to be exact (two for each side, one high, one low), in conjunction with one ballast resistor on each side, mounted on or near the frame rail, further to the rear than the fans.

The relays are located on the bottom row of the relay tray (there is a row below that one, but it's "unoccupied"), which is mounted directly above the fuse panel, high on the kick panel by your left calf as you sit in the driver's seat.

Here is a photo of the relays and their location:

The red arrow points to the top of the "dead pedal", the blue arrow points to the top right of the fuse panel, and the four green arrows point to the fan relays. Note that the number "53" is washed out in the photo, but it should be on your relays.

The resistors get hot and when they get splashed with cold water or rain, they crack internally and go bad.

Here is the ballast resistor (at the end of the green and white wires):

Here is a closeup of what it looks like:

There is a way to jump the relays so that you can isolate the problem, and it was discussed on another forum. If I find the link, I'll post it here.

Regards, Maurice.

Edited March 4, 2011 by 1schoir

[white99c2]

Here's the link you're looking for.

My link

Edited March 5, 2011 by azrob