Engine running warm

[skattrd]

Hi all,
according to the temp gauge in my Spider (2l carb) the engine runs a bit warm, when stationary the needle goes higher. The rad fan is on a manual switch, so I just turn it on and the temp stays out of the red.
The previous owner said it had been like this when he had it as well. he replaced the thermostat to try and cure it, but that had no effect. I've given the coolant a good flush and that made no difference. The radiator is larger than standard and relatively new, so I don't think that's the problem.

My thoughts are: dodgy temp sender to the gauge in the car, slight blockage in the solid pipe that runs across the top of the engine, or the water pump is on it's way out.

Should I just start with the easy/cheap options first (temp sender & clean the pipe out) or is there something else I should be looking at?

Cheers
Chris

[MattNoVAT]

Personally I would start by changing the the water pump and stick a new belt on.

Better to be safe than sorry.


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[skattrd]

Thx for the reply Matt, the more I think about it the more I think it may be the water-pump as well.

I've just had a quick check in HBOL and it's slightly confusing, no surprise there.
From looking at the pics in the book it appears the water pump is driven on the same belt as the alternator, not the cambelt - is this correct?
If so it'll save me doing the cambelt, as this was done last year.

edit: reading the thread below this one confirms the water pump could possibly be done without removing the cambelt.

[Thotos]

The water pump is driven by the same V belt as the alternator so the cambelt doesn't need to be disturbed to change the pump. But if the pump belt is not slipping (i.e. pump turning at normal speed) and the pump is not leaking, what possibly could be wrong with the pump that would cause overheating? The impeller is fixed to the shaft so extremely unlikely to be slipping. If the pump is not leaking and not making strange noises then I'd say with some certainty that it's not the problem.

[skattrd]

The pump isn't leaking or making any funny noises that I'm aware of.
My thoughts on the water pump were that the impeller might be damaged, missing a blade or have a worn bearing. The only  way to check is to remove it and if I'm removing it I may as well replace it, and the belt at the same time. If I'm going to drain the system to change the pump, I may as well remove the hard pipes and check for blockages whilst the coolant is out ... I may be tuning this in to a larger job than necessary, but I'd like to get it fixed in one hit.

[Thotos]

True in everything you say but a warn bearing will make a noise and a missing impeller blade (unlikely as they are metal - not plastic as some modern cars!) would soon wear the bearing and cause noise and leaking.

The manual fan switch is OK as a backup but definitely not right if it's the only way to get the fan to come on. Make sure you have an auto fan switch of the correct temperature fitted. Also make sure your new thermostat is of the correct temperature. There are a lot of similar blender thermostats and they vary in temperature opening from about 84 degrees to 94 degrees. Also don't necessarily trust the thermostat because the previous owner changed it. I bought a brand new old-stock thermostat for the Gamma from Omicron and it didn't work! I'd guess that your problem is either the thermostat or the radiator; you'd be surprised how quickly a radiator can build up scale if the system is filled with just water (no antifreeze) and there's no auto fan switch so the engine gets hot a few times. 

[MattNoVAT]

I should have been clearer in my description, when I say put a new belt on, I meant V belt, rather than cam belt.  I dont know how old it is but I've seen them glassy and also age fatigued - if it snaps you diminish electrics and lose cooling.

[skattrd]

If the fan switch is usually on the radiator then I'll say it hasn't got one, as it has a non-standard radiator fitted. A new radiator fan with thermo-switch is on my to-do list.
I can check the thermostat when I drain the coolant, but if turning the fan on lowers temps then I would assume the thermostat is working, if it wasn't I wouldn't expect the rad fan to lower temps. Bad water circulation seems more likely to me.

[Thotos]

turning the fan on lowers temps

Now I am confused!    If turning the fan on lowers the temperature then there's no problem. You just need to make sure the fan turns on at the correct temperature and turns off when the temperature drops.

[skattrd]

Lol Thotos, sorry I didn't mean to confuse you.

When the car is driving normally the needle is over half way towards the red and when stationary with the fan on it is only just out of the red.
I would  like the temperature to stay around the middle of the dial (as it does on my HPE VX). With this car the temp is always near the red part of the gauge.

[lukasdeopalenica]

Are you sure that your engine overheats, or just you believe in the gauge indication? I would suggest to check the gauge first for example swapping with the correct one.

[skattrd]

Thats the thing Lukas, as I said in the first post, it may just be a faulty temp sender ...

[peteracs]

Thats the thing Lukas, as I said in the first post, it may just be a faulty temp sender ...

Yes, I could believe that (and it may be faulty as well), but I would not have expected the reading to vary so much when the engine was put under stress/idle, which you appear to say it does. I have removed the two metal water rails on my engine and there was certainly a buildup inside the pipes, so better to be safe than sorry I figure. Personally I would also change the sensor to get a 'second opinion' as to what is happening before I dismantle, but would not be surprised if further investigation was required.

Peter

[rachaeljf]

How has the thermostat been "removed"? The thermostat is double-acting. When the coolant is cold it is recirculated back to the block to give a faster warm-up. If you remove the thermostat you leave a permanent short circuit that will hamper the flow through the radiator.

[skattrd]

Quick update, I fitted an aftermarket cooling fan with variable thermo switch. The car's running temp is just below the red on the gauge and that is about 85C according to the new switch. The gauge in the car is over-reading by the looks of things, so that's the first thing I need to sort out. I still think there may be an issue with the coolant flow though, but getting a bit more of an accurate reading in the car needs sorting first.

[Thotos]

But where is the thermoswitch 'sensing' the temperature? If it's on the radiator then you may have 85 degrees at the radiator and 95 degrees in the head where the gauge 'reads' the temperature and that would imply a thermostat fault. I thought you said that when driving normally the gauge reads OK so that would suggest that the gauge is fine.

[skattrd]

The new switch is sensing the temp on the top water rail, just after the head and before the rad. There could be a bit of a drop between the sensors though.
The temp under normal driving has always been showing a bit on the hot side.

I suppose I should drain the coolant check the thermostat is working and have a look at the solid pipes.

Any suggestions for cleaning the solid pipes? I was thinking of some caustic oven cleaner or drain cleaner, then very thoroughly rinsing afterwards.

[Thotos]

Temperature at the top hose should be quite close to the water temperature in the head.
In my Trevi, the temperature needle normally sits just above half way mark on the gauge and rises to about 3/4 way on the green sector when idle in traffic. At that point the cooling fan comes on for 20-30 seconds and then goes off so it's regulating the temperature correctly. I always assumed that the gauge readings were normal for a Beta.

The metal pipes are quite large diameter so I'd guess unlikely to be the problem. Maybe putting them in a large bucket with a lot of kettle discaler might clean them? There's a number of liquids you can buy and put in your cooling system to clean it while running but I'd be very scared to use anything like that.

[spud]

Temperature at the top hose should be quite close to the water temperature in the head.
In my Trevi, the temperature needle normally sits just above half way mark on the gauge and rises to about 3/4 way on the green sector when idle in traffic. At that point the cooling fan comes on for 20-30 seconds and then goes off so it's regulating the temperature correctly. I always assumed that the gauge readings were normal for a Beta.

Normal would actually be fractionally below the half way mark on the guage.

There's a number of liquids you can buy and put in your cooling system to clean it while running but I'd be very scared to use anything like that.

These are perfectly safe to use- the best one I think being this one from Halfords: http://www.halfords.com/webapp/wcs/stores/servlet/product_storeId_10001_catalogId_10151_productId_274607_langId_-1_categoryId_255217
No doubt it's available from other retailers too, and probably cheaper, but they won't have that fit chick on the till... 

Andrew.

[Thotos]

..... but they won't have that fit chick on the till... 

Please tell us where your Halfords is. It's so different to my local ....