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BJ8 Overheating

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specialsports

specialsports

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GregW

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Hi Brian,
Are you sure the thermostat is accurate? The capillary tube looks very short, like it was cut and re-soldered. Unless the excess is tucked up under the dash.
 
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specialsports

specialsports

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Hi Greg
No I am not sure if the thermostat is working correctly. I am thinking of taking it out altogether, car not used in the winter so not needed. The tube is coiled behind the dash. The engine bay and left side of the interior is very hot.
Brian
 
glemon

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Lots of things can lead to hot running, timing off, esp. too much advance. crud buildup in the radiator or motor.

You can test your temp guage by taking it out, putting the business end in a pot of water and bringing to a boil and it should be at the H end or if you have numbers around 212.

EZ things that help a little--higher concentration of water to anti-freeze, water is actually a better cooler, no problem running mayb 2/3 3/4 water and you will get better cooling than a 5050 mix. Redline Water Wetter is a product moss sells that is supposed to help cooling action of the water/anti-freeze mix. I and others have reported a 5-10 degree improvement in cooling.

Electric Fans--I don't have one, but have read a lot about them, sometimes they work great, I also know people who have installed them to find that the car cools worse with the fan, esp. at speed.

If the thermostat was stuck shut you would know it, car would get very hot and start making bad noises in a hurry, if stuck open car won't get up to operating temp as fast, more if an issue in cold climate operation as you mentioned.
 
M

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Hi Brian,

Is the overheating problem new or have you always had this problem? If it is a new problem, have you made any recent adjustments or changes to the engine and/or engine compartment?

Mark
 
Dave Russell

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specialsports said:
Hi Greg
No I am not sure if the thermostat is working correctly. I am thinking of taking it out altogether, car not used in the winter so not needed. The tube is coiled behind the dash. The engine bay and left side of the interior is very hot.
Brian
Click to expand...
The thermostat in your car (six cylinder) was originally a special designed sleeved type. The cooling system is designed to bypass the coolant from block to cylinder head when the thermostat is closed, & coolant is shut off from the radiator.

As the thermostat opens, a sleeve on it closes the block to head bypass port & allows full coolant flow through the radiator instead of bypassing part of it through the cylinder head.

Many folks replace the original expensive ($45) sleeved thermostat with a cheap ($5) conventional type. As a result, part of the coolant always bypasses the radiator when the thermostat is open & can cause overheating.

In my opinion, this would be the first thing to check.

If you totally remove the thermostat with it's accompanying restriction, the water pump may be subject to cavitation, & the dynamic water pressure in the head will also be reduced & cause localized hot spots. The restriction of the open thermostat is needed to reduce both problems.
D
 
Patrick67BJ8

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specialsports said:
Hi Greg
No I am not sure if the thermostat is working correctly. I am thinking of taking it out altogether, car not used in the winter so not needed. The tube is coiled behind the dash. The engine bay and left side of the interior is very hot.
Brian
Click to expand...
I have been told to always have a thermostat. On my last engine "go through", I replaced the "aftermarket" thermostat with the correct type & style. British Car Specialst has the correct ones. I also put in an american core in my radiator. It has 25 to 30% more cooling capacity(done locally in Dallas). I also put in a new electric fan with thermostat adjustment control and it works great even in traffic wuth the AC "on". No more overheating problems. Although my original core looked good, once the top was taken off the radiator it was a whole different story.
Patrick
 
Dave Russell

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One thing that folks don't consider is that as a radiator ages the solder bonds between the outside of the tubes & the fins gradually deteriorate. This causes loss of thermal conductivity & loss of cooling ability. Even if the tubes are not noticeably plugged, a new replacement can often improve cooling. As Patrick said, a good time to also replace the core with a more modern & effecient design.
D
 
healeynut

healeynut

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If you are in the UK and you are getting this result, I would have to say it sounds to me your thermostat is sticking. take it out and check it. If it is ok, then I would consider doing a complete flush of your block.

FYI, the stock radiator fan will move more air than an electric kenlowe. Is it still on the car?
 
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specialsports

specialsports

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Lots of info to check, many thanks. Yes I still have both fans in the car. The only thing that I have done this year is to fit a new pump and a new stat, also had the original rad checked and flushed out by a rad firm.
Brian
 
healeynut

healeynut

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Brian -

Yeah, if you've only flushed the radiator (it should have been rodded by the rad firm) then the block could be completely crudded up. You have to do a complete flush of the block, maybe even consider a 20 minute run with 50/50 white vinegar and distilled water to really flush it out.
 
nevets

nevets

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if it turns out that problem is not related to the cooling system, it may be worth checking the ignition timing? just a thought.
 
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specialsports

specialsports

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I did have the timing checked by a so called expert, he said he had altered it to the correct timing. OK now what do you think should be the correct timing for today's cars, is it still as the book of 40 years ago? also with my engine being modified would this effect the timing? The flushing out of the engine sounds good, what is the procedure and what do I use with engine in situ?
Regards Brian
 
healeynut

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specialsports said:
I did have the timing checked by a so called expert, he said he had altered it to the correct timing. OK now what do you think should be the correct timing for today's cars, is it still as the book of 40 years ago? also with my engine being modified would this effect the timing? The flushing out of the engine sounds good, what is the procedure and what do I use with engine in situ?
Regards Brian
Click to expand...

Brian - RE flushing the block note my post above. Vinegar (acetic Acid) is quite good at removing scale and a mild etch on rust. It's a good prep for clean fluid. Don't forget to check your thermostat...

Cheers!
 
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specialsports

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OK Thanks for info. Do I just bring the car up to temp or run for 10 miles with this fluid in, before I drain and refill? I am going to check the thermostat, I now think I could have a problem with my original distributor, I am convinced this is my problem, ref vacuum, A/R, springs etc. So I am now thinking of fitting a Mallory dist, have you had any feedback ref: this item or similar?
Brian
 
healeynut

healeynut

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I know people talk alot about advance causing overheating, but my view is if your car is overheating, regardless of the dizzy advance, it means you have a problem in your cooling system somewhere.

With respect to your dizzy, I don't see any point going to a Mallory in of itself unless it is packaged with a complete build/tune of your motor. If you are just replacing it to fix it, I would then first consider going with rebuilding your dizzy (try jeff @ advanced distributor in the US) or if you are looking for a pretty cool upgrade unit, swap out for a 123 Ignition from the netherlands.

https://www.123ignition.nl/id/28.html

This electronic ignition unit uses standard bosch rotor and cap, and has 16 different advance profiles + vacuum advance (which the mallory doesn't have).

Cheers.
 
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specialsports

specialsports

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Hi Yes we have these in the UK, I can pick one up for around £180.00. The most important thing about this unit is that it will operate Neg and Poss earth also has the facility for rev-counter take off. I am in the process of replacing the stat plus a full flush of the system including the rad.
Brian
 
Ed_K

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Dave Russell said:
One thing that folks don't consider is that as a radiator ages the solder bonds between the outside of the tubes & the fins gradually deteriorate... D
Click to expand...
I found out last week that the fan guard is also soldered on and is subject to the same deterioration of the solder . Two of the three attachment points were loose and I was lucky to spot it before the last solder connection gave way. I gently rocked the fan guard back and forth and the third remaining solder joint gave way. Now I have another reason to pull the radiator this winter besides to have the old core upgraded !
Ed
 
healeynut

healeynut

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specialsports said:
Hi Yes we have these in the UK, I can pick one up for around £180.00. The most important thing about this unit is that it will operate Neg and Poss earth also has the facility for rev-counter take off. I am in the process of replacing the stat plus a full flush of the system including the rad.
Brian
Click to expand...

Brian -

Let us know how it all goes.

Cheers...
 
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