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Alloy Heads and towing, how to help with overheating probs.

Submitted: Wednesday, Apr 02, 2008 at 19:25

Member - Axle


Was sitting with a group of tradies the other day at lunch, and
the conversation of towing with cars, trucks, etc, got underway, ...lol, but one guy made a statement that i've taken on board; and that was inregard to towing up a looong hill, then going down the other side, letting it go down on overrun with a tap on the brakes now & then. Not good for alloy heads as temps rise a lot more than shown on the guage, so its better to try and drive with a bit of throttle so as not let it cool to quick when on the down hill run.

Not allways possible, but alloy heats and cools very quick, so in my opinion i think he was right in what he said.

CheersAxle
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AnswerID: 296222   Submitted: Wednesday, Apr 02, 2008 at 19:51

Member - David P (VIC) replied:

so the theory is that the thermostat doesnt do its job ????

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silverback
Reply 1 of 5
FollowupID: 562284   Submitted: Wednesday, Apr 02, 2008 at 19:59

Member - Axle posted:


The thermostat dosen't control how quick it cools from one temp to another, :)).


Cheers Axle.
FollowUp 1 of 3
FollowupID: 562295   Submitted: Wednesday, Apr 02, 2008 at 20:35

zacc posted:

i would have thought that the thermostat would start to close as the heads cooled down thus holding the heat in . the thermostat would open and close a lot faster that the head or heads could heat up and cool down , thus keeping the engine at the right temperature.
FollowUp 2 of 3
FollowupID: 562298   Submitted: Wednesday, Apr 02, 2008 at 20:40

Member - Kiwi Kia posted:

Axle, as soon as the water temp goes down to the opening temperature of the thermostat it shuts and keeps the engine warm. Radiator will cool rapidly but the engine block will stay warm till it is cooled by airflow. The engine is still ticking over and hot oil is still being circulated and the engine should be cooling evenly.
FollowUp 3 of 3
AnswerID: 296239   Submitted: Wednesday, Apr 02, 2008 at 20:34

Davo_60 replied:

It may cool quicker with a little throttle given the increased water flow and fan speed. Just surmising as I try to keep a little throttle on after a big climb to keep the fan and water pump working a bit faster in an effort to keep cooling.

Cheers,
Dave
Reply 2 of 5
FollowupID: 562345   Submitted: Thursday, Apr 03, 2008 at 05:42

pt_nomad posted:

Davo,
my experience with a LC105 1HZ is that this is one of the most dangerous times as far as EGT is concerened. AFtr cresting a hill the tempation is to hold full throttle to allow the vehicle to build up some of the lost speed making use of the down hil run. My observations is that this action consistantly and v. easly this sends EGT into the 700+ region with very little effort.
So after cresting back off 30% for 10 secs and then poke the loud peddle to get some speed.
Paul.
FollowUp 1 of 2
FollowupID: 562488   Submitted: Thursday, Apr 03, 2008 at 18:45

Davo_60 posted:

Thanks Paul,

I think we are talking about the same thing. I back off at the top of a hill but not to the point of no throttle. I will usually leave it in third (4 speed auto) to keep the revs up a bit until EGT drops and temp starts to reduce, then slip it into top.

Cheers,
FollowUp 2 of 2
AnswerID: 296240   Submitted: Wednesday, Apr 02, 2008 at 20:39

Mick15 replied:

yea, i see what they are saying, obviously that wouldn't apply to a diesel as it will run cooler when lean, but with aluminium it conducts heat roughly 4 times the rate of steel,
Therefore i would assume that if there was any excessive heat generated then it would be wicked away from the combustion chambers fairly quickly and provided the cooling system is in good nick should then be transfered away...
Maybe if your coolant level was low or had an air pocket in the head there could be problems though, i'd still think that there would be more heat generated going up a hill under full power.

imho :)
Reply 3 of 5
AnswerID: 296256   Submitted: Wednesday, Apr 02, 2008 at 21:12

Member - David P (VIC) replied:

you may not think you need anti-freeze, but it is an important anti-cavitation component, that is the formation of bubbles in areas of high turbulence eg the water pump impeller vanes which tend to gather in the highest part of the engine , the cylinder head combined in many instances with turbo and or supercharging The modern engine is being pushed to its limits to satisfy the requirements of reduced emissions, increased power and reduced consumption......silverback

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silverback
Reply 4 of 5
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AnswerID: 296321   Submitted: Thursday, Apr 03, 2008 at 09:10

DIO replied:

By allowing vehicle to coast ('angel over-drive') you not only run the risk of loosing control through increased speed but with engine only idling (say 500 - 700 rpm) water is not being circulated as quickly throughout engine/radiator as when say engine revs are at 1500 - 2500 (or whatever). If water pump is engine driven why not consider a electrically driven unit. Added benefit of increase in engine power and greater cooling efficiency. Link
Reply 5 of 5