Car overheating or normal behaviour?

After the wiring mess I described in my post from yesterday, I put on the new cluster and went to the MOT.

In Portugal, where I live, it was about 40ºC outside today. While I waited in line for the inspection, I took a picture of my dash.

What I want to know is if my temp is correct or if I need to buy another thermostat and radiator fan switch to others with a lower temp margin.

My car works as follows:

The fan kicks in when the temp gauge is right after the 3/4 white dot mark. Then the car cools a bit (just a bit!) until the gauge is right before the 3/4 white dot mark on the dash and the fan turns off. Rinse and repeat.

This is the behaviour with the car stationary. Sure, it doesn't passes the 3/4 mark but still, I think it's running too hot, no? I'm used to gauges holding vertically at 90º

If i'm moving, the temp will be a little lower and constant but almost always passing the middle of the temp gauge.

Here's an image:

That seems too high. Fair enough in 40 degrees but not all the time. Have you flushed the system lately? First and cheapest thing to try perhaps.

Yes, I did. And used G12 coolant.

The car had a head gasket replacement about two months ago. The thermostat opens up, as I can feel the lower tube getting hotter about the same time as the radiator fan kicks in.

The switch for the radiator is also new.

I really thought that the 3/4 was the normal operation temperature for these engines. I must say that the gauge never passes that mark but yeah, I would really prefer it to be on the 1/2 mark (and maybe starting the radiator fan right after that). 

Did you buy a thermostat that was the same temp as the radiator switch?

You can wire a override switch on the Radiator fan circuit.

I have seen these temps, when I am in stop and go, or I drive off the highway to a side street and stop the temp will climb.

If you don't have radiator cards (upper is needed) then your fans can suck in engine compartment air over the radiator instead of the grille.

is your ride an automatic? they run hotter than a manual.

You are describing normal behavior..

To be fair I don't remember the temperature of the thermostat or radiator fan switch. I just gave the brand and model of my car and the guy from the parts store gave them to me. I trust their correct, but yeah, maybe I'll recheck. Should I buy any specific temperature ones?

The car is a manual one. I've been reading this forum and i've read that the temp should drop to about 1/2 after the fan kicks in. Mine doesn't do that much. However yeah, I took this photo with the engine running after a while and the car stationary on a very hot day. I was waiting in line for my time in the MOT.

I do have the upper radiator card but not the side ones. I lack the molds for the side ones for my small radiator.

But this got me thinking:

- I've seen a thermostat on autodoc that opens at 71ºc.

Is this too low for the engine ideal operation temperature?

- Or should I drill a 3mm hole on my current thermostat?

Also, do you think I should request a fan switch with a specific temperature range? I don't know the one I have, but I've seen some that work in the range of 84ºc to 95ºc (the fan would start when the coolant reaches the 95ºc and stop when it's on the 84ºc). I'm inclined to buy it. What do you think?

Questions… so many questions… 

A little further over than I've seen mine but I don't think it's ever ever ever been 40c in northern England.

You don't mention that its losing water or boiled up so I'd say ist working as intended

Yeah, it's not losing coolant

mpercheiro said

Yeah, it's not losing coolant

and  if the warning light doesn't flash I'd leave well alone

Yes, it doesn't either.

I was just a bit alarmed has everybody tells me that the car is very hot and to be fair I don't know the normal operation temperature.

The problem is the temperature gauge isn't calibrated, and there's a lot of leeway in the temp gauge and sensor. Combine it with ~40 year old wiring, and there is no one single temperature reading which is "right" and even that high, you can't really say its overheating.

You don't mention which engine your car has but you said it had a "small" radiator - which one? GTIs had a 525mm radiator, 1.5 had a smaller one (430mm?), not sure on the 1.8 carb though.

mpercheiro said

Yes, it doesn't either.

I was just a bit alarmed has everybody tells me that the car is very hot and to be fair I don't know the normal operation temperature.

To be honest, in stop and go traffic where you don't have constant cool air flow over the radiator that is about normal for city driving.  3/4 to half is normal for highway driving.

On the pre90 cabriolets VW used a water stabilized oil cooler, that ties the engine oil temp to the coolant, which makes the car heat up quicker, but can lead to excessive heat. On the 90's Cabriolets over here they took the oil/water coolers off.

Now with that said you can calibrate your gauge, by using a infrared thermometer on your engine to tell you the accurate temp of the engine, then look at your gauge.   Using various resistors on the ground portion of the sense wire you can add resistance to lower the gauge to the engine temp..

I know that after I added an external oil cooler to my 90, 92, and 93 I dropped the operating temp of the engine, as I could see the oil temp go from 130 to 105.  I also noticed a drop in the coolant as well.  

I went so far as to exchange the radiator from plastic/aluminum to a all aluminum radiator (increased width of core, and a tad longer, I did have to remove the bosses on the front to seat it correctly, (used a dremel to grind them) and remake the upper radiator card I noticed a bigger drop of coolant temps. Also if you are going to ever exchange your water pump make sure you have a metal impeller, not a plastic one.  I installed a Salari Pump on my cars and its radical impeller pushed more water, lowered the operating temp, and worked well, but failed after about the 4th year.

See The truck formerly known as The 'NONSMKR': Driven to build | Page 19 | VW Vortex - Volkswagen Forum

The last page he uses resistors to Calibrate his coolant temp gauge.

paul_c said

The problem is the temperature gauge isn't calibrated, and there's a lot of leeway in the temp gauge and sensor. Combine it with ~40 year old wiring, and there is no one single temperature reading which is "right" and even that high, you can't really say its overheating.

You don't mention which engine your car has but you said it had a "small" radiator - which one? GTIs had a 525mm radiator, 1.5 had a smaller one (430mm?), not sure on the 1.8 carb though.

Along with different widths they also came in 2 depths/thicknesses, 34mm and 42mm

Always when replacing the Radiator use one designed for a/c increased width and length.

There are also someone on the web that has a Cabriolet style fasteners for the upper radiator. that is the 2 metal clips screws and nuts.

Another gimme:
When you replace the t-stat, drilling the 1/8 hole in the lip prevents the air-bubble from improper filling of the coolant system.

Before I started to drill mine, you pull the upper radiator hose and loosen it off the cylinder head.  Fill half your fluid from the hose to the Cylinder head until it dribble out the upper fitting on the flange.

Cold engine, open the heater to full hot.

Then take the hose off the coolant flange, and put it back on the radiator, and fill your radiator from the hose
Till it dribbles back out.  You then burp the upper hose, and replace it and tighten both clamps.

Start the car, and fill the expansion jug (even with the seam). and as the car is warming up verify that the return in the tank is pushing water and air until a steady stream, and burp the hose.  Replace the cap run the car until the radiator fan cycles 2 times.  Turn it off and allow it to cool off, then top off the expansion jug.

The hole that you drill in the lip of the t-stat prevents the air bubble at the stat, buy letting air through the t-stat filling both sides.  Some folks drill it, some don't but as long as I was driving my Rabbit, I think I started to drill mine after about the 15th year.

Hi guys, sorry for just answering now. I've been (finally) enjoying my Cabrio Gotta enjoy the nice weather. Thank you all for your replies, they were of great help and also the reason why I truly believe this to be onde of the best VW related forums of the entire internet. Great community, no doubt about it.

paul_c said

The problem is the temperature gauge isn't calibrated, and there's a lot of leeway in the temp gauge and sensor. Combine it with ~40 year old wiring, and there is no one single temperature reading which is "right" and even that high, you can't really say its overheating.

You don't mention which engine your car has but you said it had a "small" radiator - which one? GTIs had a 525mm radiator, 1.5 had a smaller one (430mm?), not sure on the 1.8 carb though.

From “Car overheating or normal behaviour? ”

  My radiator is a small one, with 430mm. I was thinking about changing the fan switch for one that would open at 84º and shut at 95º. Maybe that'll help. Also, I have the upper radiator card, but i'm missing the side ones. I don't know where to find the moldings for it but I definitely want to do that too.

Briano1234 said

mpercheiro said

Yes, it doesn't either.

I was just a bit alarmed has everybody tells me that the car is very hot and to be fair I don't know the normal operation temperature.

 To be honest, in stop and go traffic where you don't have constant cool air flow over the radiator that is about normal for city driving.  3/4 to half is normal for highway driving.

on the pre90 cabriolets VW used a water stabilized oil cooler, that ties the engine oil temp to the coolant, which makes the car heat up quicker, but can lead to excessive heat. On the 90's Cabriolets over here they took the oil/water coolers off.

Now with that said you can calibrate your gauge, by using a infrared thermometer on your engine to tell you the accurate temp of the engine, then look at your gauge.   Using various resistors on the ground portion of the sense wire you can add resistance to lower the gauge to the engine temp..

I know that after I added an external oil cooler to my 90, 92, and 93 I dropped the operating temp of the engine, as I could see the oil temp go from 130 to 105.  I also noticed a drop in the coolant as well.

I went so far as to exchange the radiator from plastic/aluminum to a all aluminum radiator (increased width of core, and a tad longer, I did have to remove the bosses on the front to seat it correctly, (used a dremel to grind them) and remake the upper radiator card I noticed a bigger drop of coolant temps. Also if you are going to ever exchange your water pump make sure you have a metal impeller, not a plastic one.  I installed a Salari Pump on my cars and its radical impeller pushed more water, lowered the operating temp, and worked well, but failed after about the 4th year.

See The truck formerly known as The 'NONSMKR': Driven to build | Page 19 | VW Vortex - Volkswagen Forum

The last page he uses resistors to Calibrate his coolant temp gauge.

From “Car overheating or normal behaviour? ”

Thanks Briano1234, that was an excellent advice. I'll definitely do that too. Measuring the real temperature seems a great way of knowing the right temperature and then calibrate the gauge. Yes, my engine (RE engine - I haven't seen many of these) does warm up quite fast, it is probably related to the oil temperature like you wrote. Where can I find a oil cooler for these cars?

Early-1800 said

paul_c said

The problem is the temperature gauge isn't calibrated, and there's a lot of leeway in the temp gauge and sensor. Combine it with ~40 year old wiring, and there is no one single temperature reading which is "right" and even that high, you can't really say its overheating.

You don't mention which engine your car has but you said it had a "small" radiator - which one? GTIs had a 525mm radiator, 1.5 had a smaller one (430mm?), not sure on the 1.8 carb though.

 Along with different widths they also came in 2 depths/thicknesses, 34mm and 42mm

From “Car overheating or normal behaviour? ”

While i'm not sure, I do believe mine to be the thiner one which it doesn't help at all…

Briano1234 said

Always when replacing the Radiator use one designed for a/c increased width and length.

There are also someone on the web that has a Cabriolet style fasteners for the upper radiator. that is the 2 metal clips screws and nuts.

Another gimme:
When you replace the t-stat, drilling the 1/8 hole in the lip prevents the air-bubble from improper filling of the coolant system.

Before I started to drill mine, you pull the upper radiator hose and loosen it off the cylinder head.  Fill half your fluid from the hose to the Cylinder head until it dribble out the upper fitting on the flange.

Cold engine, open the heater to full hot.

Then take the hose off the coolant flange, and put it back on the radiator, and fill your radiator from the hose
Till it dribbles back out.  You then burp the upper hose, and replace it and tighten both clamps.

Start the car, and fill the expansion jug (even with the seam). and as the car is warming up verify that the return in the tank is pushing water and air until a steady stream, and burp the hose.  Replace the cap run the car until the radiator fan cycles 2 times.  Turn it off and allow it to cool off, then top off the expansion jug.

The hole that you drill in the lip of the t-stat prevents the air bubble at the stat, buy letting air through the t-stat filling both sides.  Some folks drill it, some don't but as long as I was driving my Rabbit, I think I started to drill mine after about the 15th year.

From “Car overheating or normal behaviour? ”

Thanks for the tips regarding the coolant flush too. I will do it again as I have also to change the brake fluid and i'll do it all in one "session".