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2001 C4 Cab 60k miles. I am pretty sure I have read all 100 threads on this but was hoping I could get some input on whether I am reaching the right conclusions applying what I think I have learned. thanks in advance!

The facts:

Couple months ago:

- Had scheduled major service at the dealer when I bought it 6 mos ago (before learning about this forum).

- Coolant is between min and max - closer to max

- Months ago coolant leaked at cap --> replaced months ago no leaks since

- Replaced a dead pass side radiator fan --> works fine

- Fixed driver side ballast resistor --> both fans run at high and low

- Vacuumed radiatiors from front (really the AC condenser in front) - did the fan from wheel well.

- Last night on the 50 min commute home in 80f ambient:

- Did the HVAC diagnostic 6c hack and those are the source of the temps below not the crap gauge

- Warmed up to 80 F ambient in Boston for drive home last night - lots of stopping in traffic with a/c on and temp was up 107c / 225f after about 20 min and pretty much stayed between 105-107c the rest of the 30 min drive in stop and go.

- turned a/c off ---> no difference in coolant temp

- Once I got going for a few minutes of low rpm 40-50 mph the temp did not fall hardly at all from 106-7c, did not see the kind of cooling capacity that I would have expected (makes me think not a thermostat issue but what do I know, maybe its not opening even at really high temp?).

- Noticed about 4oz of coolant on garage floor under front of car after it sat for 20 min hot.

- Drove to work in 50f ambient this am and it was around 90c the whole time, even sitting in traffic it could cool from 96f to 90f.

- Its going to drive me nuts all summer watching the coolant temp hang around 225

The questions:

- I have seen a lot of comments that 190-200f is spec, 210 is ok, maybe at the high end, but 225 all summer can't be good right?

- Is the front coolant leak a sign of an underlying problem that is causing the high temp or just temp/pressure getting too high and finding the weak spot?

- If i vacuumed from the front, did I likely solve that problem or have people found packed in crap plugging radiator and killing its efficiency and I really need to remove front bumbner

- tempted to do the LN 160f T-stat but somehow think that is not going to solve this particular problem, though it might mitigate the symptoms?

- Is this really a problem?

- Does it look like a water pump issue if all these other things seem to be ruled out?

Any help greatly appreciated. thanks

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I would test the CAP first to make sure it holds the correct pressure and make sure it also opens at hiher pressure.

Then pressure test the whole cooling system to track down and fix any leak. If nothing improves after that, it's a good idea to inspect/replace the water pump and thermostat.

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Btw, obviously you have a leak in your cooling system. When there's a leak, the system may not be able to hold enough pressure, which will lower the boiling point of the coolant. When boiling, air bubbles are formed which do not conduct heat well.

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There shouldn't be any coolant on the floor at the front of your car, My C4 has "O" rings on the radiator hoses at the radiators, if you have the same "O" rings they can get hard and maybe let the coolant escape after you've shut down the car. I would first clean out the radiators and condensers, I probably got 2 cups of bugs, leaves and debris on mine. There's a good video somewhere on how to do that which includes the removing of the front bumper. That's easy, be helpful if you had an extra set of hands. Have you exercised the over flow valve on top of the expansion tank to know it's working?

There's a lot of plumbing in the water system, if you don't have one of the vacuum tools to use when filling the system, then I would get one, or borrow one. If you have a leak, then you might have air in the system. I assume that since you had a major service they replaced the coolant with the red/pink OAT coolant? Be sure your engine room blower fan is working...

I guess there's always the chance someone installed the wrong thermostat, I believe it should be around 180 degrees... I've read where the water pumps can go south at 60,000 miles, but usually it's the seals that go bad first. Maybe someone can chime in and say if the water pumps can go bad without having a tell tail leak?

Was your service done by a knowledgeable Porsche dealer or shop? Bottom line for me is that it seems to be a little hotter than it should be. I like you would not enjoy the car having to monitor the temp gauge every 30 seconds.

Edited by creekman

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Ahsai is correct on all counts. I had a similar mystery leak more than a year ago ( MY00 996 C2 coupe 6MT ). Florida is hot and any defect on water cooling will show up especially in stop and go traffic.

after any normal drive around town drive, I noticed the tell tale sign of a coolant tank leak as I had drips of coolant dropping off the left rear tail pipe. then I'd notice sometimes a small spot under right front wheel. a normal pressure test showed everything to spec. so we over pressurized to about 18ppsi and found both a flex leak in the tank neck as well as a definite Rad leak. I replaced the coolant tank including the new blue cap, sensor and hoses. and got a set of new factory Rads along with all new hoses, etc.

you'll be surprised with how much road crap gets wedged in and trapped around and in between the Rads and the condensers. I was doing a major refurb and had replaced water pump, etc, so the additional fix's only made sense.

good luck. you'll get it fix'd and shouldn't have anymore issues. during summer months here my dash guage wanders from splitting the 180 mark and will wander north of it depending on the ballasts/fans kicking in.

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Good point about the correct pressure, bBunny. Also, one more important point - leave the system pressurized (at ~19PSI) for at least 20 min to give a chance for the leak(s) to show up.

OP, check out the recommended testing procedure and pressure for both the CAP and the cooling system here.

http://www.renntech.org/forums/topic/45498-how-much-pressure-to-test-coolant-tank-and-cap/?hl=cap

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I installed an LN low temp T-stat and you're right about it. While my car generally runs cooler overall it still get's as hot as it did before the change. My car did run noticeably hotter overall when I got it due to the original coolant tank cap not holding pressure, not much different then having a leak in your system.

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For starters I am going to remove front bumper and give the radiators and condensers a spa treatment. And then get the Stant pressure tester that I saw JFP recommended on another thread and see where that takes me, but I expect to be able to overpressure (20psi?) that same leak up front into exposing itself. Many thanks for the help!

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For starters I am going to remove front bumper and give the radiators and condensers a spa treatment. And then get the Stant pressure tester that I saw JFP recommended on another thread and see where that takes me, but I expect to be able to overpressure (20psi?) that same leak up front into exposing itself. Many thanks for the help!

Do not over pressure it please and check post #6 above :)

You also need to get an adapter ($20 or so and doesn't come with the Stant tester) to check the CAP if so wished. BTW, the Stant testers are now made in Mexico but the good news is they are cheaper now at $70 or so.

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For starters I am going to remove front bumper and give the radiators and condensers a spa treatment. And then get the Stant pressure tester that I saw JFP recommended on another thread and see where that takes me, but I expect to be able to overpressure (20psi?) that same leak up front into exposing itself. Many thanks for the help!

Ahsai is right, don't go over pressuring these systems. If you suspect your have a leak up front, an excellent alternative is to add some Uview UV dye to the cooling system a few days before pulling the bumper, then when you do a black light will quickly show you where the leaks are:

B483906.jpg

We use this stuff to find small or hard to locate leaks in the cooling system, and the dye will not bother anything.

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- Vacuumed radiatiors from front (really the AC condenser in front) - did the fan from wheel well.

- If i vacuumed from the front, did I likely solve that problem or have people found packed in crap plugging radiator and killing its efficiency and I really need to remove front bumbner

I bought a 2 foot vacuum crevice tool and got a lot out from the front, but that was only the tip of the iceberg with respect to the bugs/leaves/feathers/dirt in the radiator. The photo shows the AC condenser hung out on a wire, and after taking off the bulk of the crud with a soft plastic brush and shop vac. After the photo I brought in a large plastic tub and the garden hose and blasted out the remaining crud.

You need to remove the bumper cover and the plastic wheel well liners. Expect to break a few of those plastic rivets getting the wheel well liners off. Mine's a 986 but the 996 should be similar.

14122511766_d4304dc1a4_c.jpg

Edited by Dennis Nicholls

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I installed an LN low temp T-stat and you're right about it. While my car generally runs cooler overall it still get's as hot as it did before the change. My car did run noticeably hotter overall when I got it due to the original coolant tank cap not holding pressure, not much different then having a leak in your system.

Hi

Following this thread since the start..... i have a leak in a couple of places (water pump, front passenger wheel well (RHD car), and elbow hose near pump). I haven't got the car up properly yet to have a look but plan to install new pump, LNtstat and hoses etc. Some very good suggestions on this thread which i will definitely take up, ask questions and report back once i have all parts above to start the job.

Just in relation to the LN thermostat, i did read the following on the website when ordering;

'Even if you have cleaned out your radiators, please be advised, some late-model cars do not report actual coolant temperature, so some users will not see any visible change in operating temperature when fitted with a 160F low temperature thermostat.'

I must admit, if i hadn't seen this, when i eventually fit it and it runs at what appears to be the same temp, i would have felt like i had been taken for a ride / something else wrong!!

I continually have my eye on the temp and oil gauges and it is almost at the compulsive stage! I need to let go. What will be will be!

Thanks

Rich

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I installed an LN low temp T-stat and you're right about it. While my car generally runs cooler overall it still get's as hot as it did before the change. My car did run noticeably hotter overall when I got it due to the original coolant tank cap not holding pressure, not much different then having a leak in your system.

Hi

Following this thread since the start..... i have a leak in a couple of places (water pump, front passenger wheel well (RHD car), and elbow hose near pump). I haven't got the car up properly yet to have a look but plan to install new pump, LNtstat and hoses etc. Some very good suggestions on this thread which i will definitely take up, ask questions and report back once i have all parts above to start the job.

Just in relation to the LN thermostat, i did read the following on the website when ordering;

'Even if you have cleaned out your radiators, please be advised, some late-model cars do not report actual coolant temperature, so some users will not see any visible change in operating temperature when fitted with a 160F low temperature thermostat.'

I must admit, if i hadn't seen this, when i eventually fit it and it runs at what appears to be the same temp, i would have felt like i had been taken for a ride / something else wrong!!

I continually have my eye on the temp and oil gauges and it is almost at the compulsive stage! I need to let go. What will be will be!

Thanks

Rich

The problem with the dash display is its gross inaccuracy, you rarely see a car where the actual running temp and dash display showing the same temperatures. Consider the temp gauge little more than an idiot light that moves; it won't tell you much except in extreme situations.

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I have a Tip so I have the 3rd radiator. I've got new coolant, a new water pump and have cleaned the radiators recently. I have pressure tested my cooling system and it's good. What I noticed after installing the LN low temp unit is the car settles at a lower temp when it first warms up and that temp is noticeably less. However on hot days driving slower speeds the temp will rise to the same max temp the system had before with the OE T-stat. I don't think the stock cooling system is effective enough to keep the car at the temperatures the LN unit (or the stock unit for that matter) open up at in all conditions. Yesterday I was in stop/go traffic in 90 degree weather and it was hot as I've seen the car get. I have a track day monday at Laguna Seca so I'm curious to see if my overall temp stays a little cooler at track speeds.

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I have a Tip so I have the 3rd radiator. I've got new coolant, a new water pump and have cleaned the radiators recently. I have pressure tested my cooling system and it's good. What I noticed after installing the LN low temp unit is the car settles at a lower temp when it first warms up and that temp is noticeably less. However on hot days driving slower speeds the temp will rise to the same max temp the system had before with the OE T-stat. I don't think the stock cooling system is effective enough to keep the car at the temperatures the LN unit (or the stock unit for that matter) open up at in all conditions. Yesterday I was in stop/go traffic in 90 degree weather and it was hot as I've seen the car get. I have a track day monday at Laguna Seca so I'm curious to see if my overall temp stays a little cooler at track speeds.

Laguna Seca..... how lucky are you! I remember playing Gran Turismo on my PS2 many moons ago...... We have nothing like that in the UK.

Mine is Tip too. I plan to do all of what you mention above (i haven't even started yet, not even a pressure test). Please can you report back once complete / any learns and helps during installation?

cheers

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If I had it to do over I would have changed the T-stat only and not bought the new housing as well. My car has headers and I couldn't move the coolant pipe completely out of the way during the housing install as the coolant pipe wouldn't slip thru the space between the headers and the T-stat housing. That made it hard to get to one of the new housing bolts. Would have been a lot quicker just to get the T-stat tool and use the stock housing.

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The whole placement of the Porsche thermostat confuses me. Rather than on the OUTLET hose, like most cars, it's on the INLET hose. Thus it's surrounded by cooler coolant coming back from the radiators. It would seem the thermostat would not be open in proportion to the temperature of the coolant leaving the engine.

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The whole placement of the Porsche thermostat confuses me. Rather than on the OUTLET hose, like most cars, it's on the INLET hose. Thus it's surrounded by cooler coolant coming back from the radiators. It would seem the thermostat would not be open in proportion to the temperature of the coolant leaving the engine.

They are just trying to keep us on our toes................. :eek:

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many thanks for all the guidance above. got the stant. waiting on the vw adapter. went to pull up on the coolant bleeder valve realized the reason it wouldn't pull up anymore is that it is permanently in the up position and can only be depressed but then it will pop it back up . is this broken? and could this be the source of my problems?

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many thanks for all the guidance above. got the stant. waiting on the vw adapter. went to pull up on the coolant bleeder valve realized the reason it wouldn't pull up anymore is that it is permanently in the up position and can only be depressed but then it will pop it back up . is this broken? and could this be the source of my problems?

Possible. The valve is spring loaded to pull the stem down. If you remove the cap, the only way to pull the stem up is to flip the metal wire to vertical position to pry the stem up. If you leave the wire flat horizontally, the stem will be pulled down by the spring.

When the tank is hot and has pressure inside, it will force the stem up and after the tank cools down, the stem again will go down.

Wire up is bleeding position. Wire flat is normal position.

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OK - Found the "leak"! - Only its not a leak. Its not coolant, its pure water coming from A/C out a drain duct between two black plastic pipes about under the passenger seat - duh! Used the new Stant 12270 and pressure sat at 19 psi for 3 minutes or so (dropped a teeny bit over 3 minutes --> one quarter of the width of the 9 font in 19 psi label.) Does that count as holding sufficient pressure? I got the VW adapter for the Stant, but I think I need something else to test the cap, but if I just replaced it with new OEM part 4 months ago I am doubting that is worth testing? Does that sound right or should I still get the part and test the new cap? I have pretty much dismissed lack of pressure as my issue. Reputable dealer did the coolant flush so I assume got the air out, but now kind of wish I got a vacuum tool. So next I went to rule out dirty radiators as the issue. I had already vacuumed the a/c condensers and the edges of the radiator through the bumper ducts and they looked good, but based on advice from this forum I removed the bumper to get behind the A?C condensers and HOLY MOSES there was a lot of dirt, former shrubbery, seeds and sand. Bought a air compressor from Harbor Freight to blow crap from back to front. Then decided I needed to blast from behind the radiator (covered condenser) and removed the radiator brackets and fans, and removed a small beach of sand from the radiators ( I drive along the coast everyday). It might be a little better but coming to work today I was at 100c-103c the last 30 min of the drive and it was only 70 f ambient so I don't think I have solved my problem. Low fans are late to kick in at over 100 without AC on. High fans kick in at 102-4c and they do drop the temp back to 100c-102c. So next step sounds like going after the water pump and thermostat? Do you agree this is worth chasing down? I am afraid that if I can hit 107c in 80f ambient, then 90f with AC has gotta get me to even higher levels. Many thanks for the input.

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OK - Found the "leak"! - Only its not a leak. Its not coolant, its pure water coming from A/C out a drain duct between two black plastic pipes about under the passenger seat - duh! Used the new Stant 12270 and pressure sat at 19 psi for 3 minutes or so (dropped a teeny bit over 3 minutes --> one quarter of the width of the 9 font in 19 psi label.) Does that count as holding sufficient pressure? I got the VW adapter for the Stant, but I think I need something else to test the cap, but if I just replaced it with new OEM part 4 months ago I am doubting that is worth testing? Does that sound right or should I still get the part and test the new cap? I have pretty much dismissed lack of pressure as my issue. Reputable dealer did the coolant flush so I assume got the air out, but now kind of wish I got a vacuum tool. So next I went to rule out dirty radiators as the issue. I had already vacuumed the a/c condensers and the edges of the radiator through the bumper ducts and they looked good, but based on advice from this forum I removed the bumper to get behind the A?C condensers and HOLY MOSES there was a lot of dirt, former shrubbery, seeds and sand. Bought a air compressor from Harbor Freight to blow crap from back to front. Then decided I needed to blast from behind the radiator (covered condenser) and removed the radiator brackets and fans, and removed a small beach of sand from the radiators ( I drive along the coast everyday). It might be a little better but coming to work today I was at 100c-103c the last 30 min of the drive and it was only 70 f ambient so I don't think I have solved my problem. Low fans are late to kick in at over 100 without AC on. High fans kick in at 102-4c and they do drop the temp back to 100c-102c. So next step sounds like going after the water pump and thermostat? Do you agree this is worth chasing down? I am afraid that if I can hit 107c in 80f ambient, then 90f with AC has gotta get me to even higher levels. Many thanks for the input.

Normally, we let pressure tests sit for at least 15 to 30 min. to see if they hold pressure. From your test description, you are probably fine.

Not surprised you found enough stuff in the radiators for your own National Geographic special; that is a common thing with these cars.

I don't remember how many miles are on the car, but the water pumps in these vehicles should be considered a maintenance item that needs to be periodically replaced.

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+1 Mine didn't show up till 20 min into the test.

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So to close this out - and for the benefit of the next guy chasing these problems down.  I replaced the water pump with new OEM pump and installed LN Engineering 160F T-Stat. Problem solved.  Old water pump impeller blades were perfect, but bearing had a teeny bit of friction so that was not the problem (at least yet). T-stat must have been the issue. Take a look at the comparison shot of the two t-stats? Does the relative shortness of that old pin look suspicious - does it push against fixed point on engine so that when t-stat expands the only way to move is the valve off the sealing surface? old one too short to push or is that normal? Final results in 50F ambient after 30 min heavy traffic stabilizes at 92C, in same conditions 70F ambient it stabilizes at 97C, where as old one stabilized at 106C.  So bottom line so far 10C or about (18 F cooler) with LN T-stat.  Might be nuts but I am feeling better. Many thanks for the help (again!). 

post-91409-0-36166500-1411152962_thumb.j

Edited by PorscheServiceThen529Plan

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