TC Running Temp

[rdssdi]

I restored my 1969 +2 years ago. I had to replace the original "minor" gauges with new Smiths gauges.

The engine has always run hot, according to the gauge. I replaced the sender, alloy rad and now back to the original recored rad with an extra row. All returned the same temp reading.

I was driving the car today and the gauge read around 100 C. It was steady at that temp. I believe at that that temp I would encounter signs of overheating which I have not.

On the Smiths electric temp gauge there are a series of two dots spaced along the bottom of the scale. They are calibration points. I used the proper resistance (ohms) for each calibration points and they were spot on. I assume the sender may be incompatible. Strange as I replaced it twice with senders that I was told were correct for the "new" gauge.

What am I missing? I have headers on the car that were Jet Hot coated. Could the sender and associated engine casting be affected by the heat from the headers?

The car runs fine. But 100+ degrees C is high. If that truly is the coolant temp. It was fun driving today. I was chased by several performance cars such as a Mustang, Porsche and more. I assume they wanted a closer look to identify the car.

Thanks.

Bob

[nmauduit]

have you confirmed with a thermometer that the engine temperature is indeed near 100?C (letting it warm up with the rad cap off and measuring the fluid when it flows)? I use a multimeter that has a thermocouple input for that kind of checks, but there are thermometers of various sort that would do the jobs. Then if the temperature is too high, did you check the water circuit thermostat (sometimes they get stuck)? I usually drill one or two 3mm diameter holes in these thermostats to make sure there is a bit of flow and that they open without the risk of a lock situation, but that is a different issue I would think (at least if you have sufficient water in the system). A possibility may also be a badly clogged radiator (poor flow, zones clogged, tubes isolated by gunk like "leak stoppers" ...). On my car running temperature is rather closely that of the thermostat : 75?C.

[Sea Ranch]

Perhaps a bit more work, but alternatively you could remove the sensor, place in a pot of water you bring up to temp, along with an accurate thermometer in the water. Compare the Smiths gauge reading to your thermometer reading. Both would be in the same pot of water. Should give a standard of comparison between your system of gauge and sensor and the thermometer.

Just a thought . . . alternative . . .

Randy

[andyhay]

I have the same issue with my car. It often reads at 100 degrees c but never runs as thought it's too hot. I recently had it checked by a mechanic with one of those temperature gun things and the engine and radiator temp was 15 c below the what the gauge indicated. So well within comfortable running temp. Should definitely check yours to be sure though.

Regards

Andy

[AHM]

With the old capillary type temperature gauge; if the bulb isn't in far enough it will read high. I replaced the fitting it screws on to for a nice new one which hadn't been chopped about and it read around 100c I put the old one back with its very short thread and it was fine.

Another thought get a ball park feel for the error by taking a reading when the thermostat opens.

[Mazzini]

With the old capillary type temperature gauge; if the bulb isn't in far enough it will read high. I replaced the fitting it screws on to for a nice new one which hadn't been chopped about and it read around 100c I put the old one back with its very short thread and it was fine.

Another thought get a ball park feel for the error by taking a reading when the thermostat opens.

I wonder why that is? I run a TTR exhaust on my S2, the number 2 cylinder manifold pipe comes up, close under the thermostat housing, it dumps heat in the wrong place and causes the gauge to read high.

[rdssdi]

All very interesting.

The temperature sender I have is electric. I wonder if the probe is too short and as with the bulb type and headers the excess heat soaks into the sender.

I have an electric thermometer with a long metal probe. I will test the coolant temperature with the cap off. I also added a threaded bung to the coolant outlet / thermostat housing (see photo). I added a bleeder to be certain there was no trapped air.

My nagging concern is , of course, that the temperature gauge is correct. I have done all I can to remove the cooling system as the culprit with the exception of the engine block coolant passages. My car had been derelict for a long time. I had the engine rebuilt by Marcovicci and Wenz (U.S. company) who were highly reccommended but they did clog the front timing chain case plate oil "weep" hole thereby denying lubrication to the valve chain causing a very premature failure. I now speculate the possibility of clogged water passages in the block as a potential problem.

Can anyone provide me with an illustration of the coolant passages in the block? I will confirm the coolant temperature with other gauges before I remove the engine (again!) to inspect and clean the coolant passages.

[nmauduit]

Was the coolant clean when you swapped radiators? Do you have an electric fan on it, and does it go on when the engine heats up?

A thorough clean up of the engine passageways may not be so easy with the engine on, but if you suspect clogging you can always remove the rad bottom hose, turn it towards a tank of sort and generously hose the engine waterways from the top, maybe with some pressure if available (possibly let it sit with a cleaning agent at some point depending on what you find e.g. oily residue, and rinsing a long time with fresh water after)... You may also be able to pressure hose the water pump (without the belt so that the impeller may rotate) if you suspect clogging there.

Actual overheating (i.e. confirmed by a know good thermometer) with a known good radiator and functional thermostat (to be confirmed, but in doubt and in a hurry you always can remove it) there are less things to worry about... including the water pump of course (not a definite test, but when the engine is hot and thermostat open you should see some flow within the circuit, at the rad cap or elsewhere - establishing a quantitative measure of pump efficiency is an other story though). If you're really concerned with the water pump, I guess you may try to test it shortly independently of the radiator top to a bucket instead (from a cold engine full of water but not flowing, only for a few seconds should not lead to overheat - or rotating it from above via a separate setup using the belt - to get a feel of how much it actually pumps). Messy garden hose plumbing (need to have the bucket high enough on a stool to avoid gravity draining or air in the hose), esp. if you want to have the inlet from a bucket too, for an outcome that would only be indicative (assess the rate at which the water goes from one bucket to the other at say 3000rpm)...

I hope it is only a sensor/gauge issue, bothering but not so urgent to solve.

[Grizzly]

Out of interest, which radiator are you using? I've never had a problem myself but it seems both my cars have been re-cored in the past (both have been upgraded to Three core), there is a guy we do work for with a 2 seater S3 who constantly complains of it running hot and he has the original as factory Radiator fitted.

I know with both my Elans (Sprint and +2) they both run around 90degree's when moving and the electric fan kicks in at 100 so they never go any higher. (BTW both have aftermarket fans fitted).

I went through a stage of getting huge amounts of Radiated heat off my Stainless manifold so i bought an IR temp gun (was only about ?20) it's great for checking pipes,temp of Rad, binding brakes etc.

[bill308]

100C (212F), the boiling point of pure water at standard atmospheric pressure, is not that high IMHO. Remember your cooling system is pressurized and likely conditioned with antifreeze, both of which raise the boiling point of the coolant. The fact that the temperature is steady, suggests that you have not yet reached the cooling capacity of the cooling system, so your temperature is likely being controlled (modulated) by the thermostat. Personally, I'd recommend an 85C (185F) thermostat.

Bill

[Bombay Racing Green]

I think the owners manual states that 85 Centigrade is normal. My S4 would consistently run at around 100 Centigrade and slightly higher during the one or two days of Summer here in Ireland. I drilled the two holes in the side of the engine bay, put some foam blanking over the radiator (it was actually the stuffing out of an old baby changing mat!) and just used straight water with water wetter. It ran at a steady 80-85 thereafter. I have changed it back to an antifreeze mix and it is about the same. It does have Stromberg carbs which I believe run slightly hotter than Webers.

I have a similar thermostat housing to yours. It a Burton power item with an integral boss. I use it for the fan thermostat switch. Probably not the best place as there may be an air pocket there but it does work. I suppose it could be used as a fill point too.

Regards,

Pete

[rdssdi]

The coolant was clean BUT there is some discoloration of the coolant in the overflow bottle.

I am running the original radiator that has been recored with an extra row. At least that is what I remember. I had open heart surgery in September and have some difficulty with memory. It is returning but not completely.

I do have an electric pusher fan and it does turn on when the coolant heats up. I cannot remember the sensor trigger temperature. The sensor is mounted in the top radiator tank right corner.

I am awaiting an IR thermometer. I will get temperature measurements at the top tank and hopefully the coolant outlet housing. That should settle the gauge accuracy issue.

I am using the Dave Bean cassette water pump. The original pump began to leak and the front cover had been damaged by the loose valve chain so I replaced it all. The hot running was also an issue with the original pump.

If I discover the engine is running hot then I will investigate a system to flush the coolant passages. Such as was described. Water and cleaner under pressure might reveal sediment.

I should have the IR thermometer by Wednesday.

Bob

[collins_dan]

I put two of these on the front of my griffin aluminum radiator and no more high temp problems.

https://www.summitracing.com/parts/prm-19128/overview/

I manually turn them on at 170F (as my trigger is set at 190F and its not adjustable) and they hold it there under almost all circumstances, maybe creep up to 190F on a really hot day sitting in traffic. I think that the thicker radiators require a bit more CFM to cool. Each of these push 2400CFM and only draw 4 amps each.

All the best,
Dan

[rdssdi]

I have a large electric pusher fan.

I now remember another issue. When I stop the engine when hot restarting is somewhat difficult.

The starter turns the engine what seems to be faster and the engine will catch and not run. It takes a few attempts to get it running. This is juxtaposed with starting from cold which is easy and usually does not require choke.

It appears to me that this would be a symptom of an engine that is too hot. I may be doing a flush clean shortly.

I read that a dishwasher soap and hot water should be used first to remove oils. Then an infusion and soaking with citric acid and hot water. Flush and repeat as necessary.

Is this correct? Other suggestions? Anyway to get a visible inspection of the block cooling passages?

Bob

[collins_dan]

I saw that you had a large pusher fan, so did I. Check the stats on the CFM for the fan you are using. Mine was 800CFM. 4800CFM makes a huge difference! Dan