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Author Topic: Overheating Paranoia  (Read 7542 times)

May 16, 2013, 07:42:49 pm

rs899

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Overheating Paranoia
« on: May 16, 2013, 07:42:49 pm »
It hasn't happened yet, but it seems to take a lot less time when sitting in traffic for the needle to creep up and the fan to come on.  Or when running before the fan comes on seems to take a bit for it to cool off.

Just for grins I pulled the front end apart and really cleaned out the fins on the condenser and radiator (original) and took off the rad and backflushed it.  It flowed just fine and really looked fine for its age.

Could the water pump impeller be going, or am I just paranoid?


'91 Jetta 1.6 NA, '82 Caddy 1.6NA, '81 Cabriolet,  4 Mercedes OM616/617s , 2 Triumphs and a Citroen DS19 in a pear tree.

Reply #1May 16, 2013, 08:26:13 pm

bbob203

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Re: Overheating Paranoia
« Reply #1 on: May 16, 2013, 08:26:13 pm »
if it doesn't go up above 3/4 i wouldn't worry is what im told.
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Reply #2May 16, 2013, 10:14:30 pm

8v-of-fury

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Re: Overheating Paranoia
« Reply #2 on: May 16, 2013, 10:14:30 pm »
3/4 is where the fan should come on, after the thermo has opened at ~180F and the rad is now subject to 195-205F coolant. The rad fan switch is in the rad, and the gauge reading is from the head.. so your gauge reads a little hotter than the system truly is.

If it is not over heating, and does cool back down when the fan comes on.. I see no worry here.

Reply #3May 16, 2013, 11:32:41 pm

TylerDurden

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Re: Overheating Paranoia
« Reply #3 on: May 16, 2013, 11:32:41 pm »
Verification is just a $20 IR thermometer away. Useful all around the house, shop, cars.

Reply #4May 16, 2013, 11:56:17 pm

wolf_walker

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Re: Overheating Paranoia
« Reply #4 on: May 16, 2013, 11:56:17 pm »
8V about nails it, but I don't like the occasional high swings myself. 

Many things we do naturally become difficult only when we try to make them intellectual subjects. It is possible to know so much about a subject that you become ignorant.
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Reply #5May 17, 2013, 12:13:42 am

damac

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Re: Overheating Paranoia
« Reply #5 on: May 17, 2013, 12:13:42 am »
I have been watching my 79 rabbit with stock thermostat and aftermarket coolant gage which is in the out port of the head piece.

I have never daily driven an mk1 and I am guessing there isn't much different between it and my 85 except the 2 stage fan?

My rabbit runs close to 190 on the gage steady going on the freeway on flat ground even at speeds of 80mph.

When I start boosting for longer periods though I see the egts rise to a max of 1350 or so thus far and the temps will increase approaching 210+ on the gage.  Can't even hear the fan at those speeds so not sure what help it is at that point.

I also do not have those side/top cardboard deflectors on this car.  I have been meaning to make up something but have other stuff to do first.

Also in idle traffic I notice within a few minutes the temps slowly rise and the fan will cycle for a bit and bring it down to normal and the cycle continues.

All my stuff is new including mk2 ac alternator
1985 turbo diesel jetta

Reply #6May 17, 2013, 01:13:15 am

wolf_walker

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Re: Overheating Paranoia
« Reply #6 on: May 17, 2013, 01:13:15 am »
Manual switch and a fan-on LED is nice to have. 
Fan shouldn't come on at speed, and the side ducts to channel air through the rad does help.

190 or 210 isn't a prob, and isn't that much of a swing really, but that hot on flat ground would bug me. 
I bet the ducting helps when you get it on there.
Some oil coolage might as well, that's another good gauge to have.


My ideal is the gauge never climbing over where it rides under normal driving.
Call it 12 o'clock on the stock gauge, which is variable of course.
I prefer the temp not to climb to 3/4 or so when stuck in traffic or such
before the fan comes on.  I don't see any good reason for it, and can think of
detrimental effects. 
Many things we do naturally become difficult only when we try to make them intellectual subjects. It is possible to know so much about a subject that you become ignorant.
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Reply #7May 17, 2013, 08:38:45 am

rs899

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Re: Overheating Paranoia
« Reply #7 on: May 17, 2013, 08:38:45 am »
I am "comfortable" so to speak with my fan/fan switch and, after cleaning and inspection, my old radiator, but still my memory from last year tells me that something is not working as well as it used to.  And, whatever it is seems to be related to low speed/low rev condition because it's cool at speed- just seems to heat up faster than I recall.  I know I will be flamed for this, but I have a 160 degree thermostat on it- that's all I have ever run on these cars for 20 years in hell.

I haven't changed anything from last year.

I have a timing belt change coming up in 5-10 k miles.  I will probably just change the water pump on principle  then because I have a new one and the one in there is just old.  Maybe I will find something there, or not....
« Last Edit: May 17, 2013, 08:40:41 am by rs899 »
'91 Jetta 1.6 NA, '82 Caddy 1.6NA, '81 Cabriolet,  4 Mercedes OM616/617s , 2 Triumphs and a Citroen DS19 in a pear tree.

Reply #8May 17, 2013, 07:45:34 pm

8v-of-fury

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Re: Overheating Paranoia
« Reply #8 on: May 17, 2013, 07:45:34 pm »
When you do the water pump, do a chemical coolant flush prior to draining the coolant.

Then add fresh stuff with a higher mix of freeze/water, and run some of the chemical "water wetter" or the likes. It effectively makes the coolant better at transferring heat. 160 thermo seems decent for Florida weather.. allows everything to start cooling back down quicker when operating temps are approached.

Reply #9May 18, 2013, 10:15:04 am

bbob203

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Re: Overheating Paranoia
« Reply #9 on: May 18, 2013, 10:15:04 am »
1350 egts? That seems critically high?!!  :o
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Reply #10May 18, 2013, 02:35:21 pm

8v-of-fury

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Re: Overheating Paranoia
« Reply #10 on: May 18, 2013, 02:35:21 pm »
When I start boosting for longer periods though I see the egts rise to a max of 1350 or so thus far and the temps will increase approaching 210+ on the gage. 

It peaks 1350, and only after extended high boost high fuel situations. Its all good.

Reply #11May 18, 2013, 08:55:12 pm

theman53

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Re: Overheating Paranoia
« Reply #11 on: May 18, 2013, 08:55:12 pm »
I don't know. I think if you hit 1350F it is OK, but if the boost doesnt bring it down then I wouldn't let it hang out there. I think 1,200F sustained is the general rule for OK, after that things get a little more dangerous.

Reply #12May 19, 2013, 08:32:16 am

92EcoDiesel Jetta

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Re: Overheating Paranoia
« Reply #12 on: May 19, 2013, 08:32:16 am »
anyone know what the rad fan switch temp is? I would like to install a lower temp switch to get the fan to come on sooner.

Reply #13May 19, 2013, 02:02:17 pm

rs899

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Re: Overheating Paranoia
« Reply #13 on: May 19, 2013, 02:02:17 pm »
^^  I don't know if this helps any (probably not) but the on temps are inscribed on the switch on your radiator.

Back to my quandry, I have another theory.

I might have a very slight head gasket leak.  I had to add about a cup of water yesterday.  I needed to add some last week too, but I chalked that up to dumping the rad and having a bubble in the upper hose.  Not, I'm not so sure.

It could be that the system is robust enough to overcome the slight leak at speed and full flow, but not at idle/low airflow.

If that is the case, should I try to tweak my headbolts again (these are 12mm stretch on my '91 Jetta) or ....?
'91 Jetta 1.6 NA, '82 Caddy 1.6NA, '81 Cabriolet,  4 Mercedes OM616/617s , 2 Triumphs and a Citroen DS19 in a pear tree.

Reply #14May 19, 2013, 03:20:56 pm

damac

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Re: Overheating Paranoia
« Reply #14 on: May 19, 2013, 03:20:56 pm »
Can you rule out your heater core?  I had this oddball problem on my 85 jetta and it was slowly seeping for like a week and I didn't notice it until one day just sitting in the garage I went out there and found a puddle on drivers side floor and tons of moldy stuff growing everywhere!  Windows were rolled up and car sat while I had time off.  Totally nasty job, had to get rid of all insulation, power wash carpet, take out dash, clean everything, etc.
1985 turbo diesel jetta

 

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