PaulBuz
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| posted on 14/2/10 at 03:40 PM |
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engine overcooling
I've only recently got my car on the road, fun, but very cold
Unfortunately, I seem to have an over cooling problem with the car, only when its driven hard on the road. (temp. is perfect when car
idles-controlling around 90 degrees c.)
When driven the temp. drops to 70 degrees, with an ambient temp. of 3-4 degrees.
I have removed the stat. & tested it in boiling water, its perfect.
The engine is the 8v dohc sierra one.
As I had to make a custom manifold for the carbs, the coolant flow is'nt as standard( using remote stat.)
I don't want to continue driving it in its present conditions for obvious reasons.
Here's my coolant flow diagram , can anyone spot a problem?
[Edited on 14/2/10 by PaulBuz]
ATB
Paul
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PaulBuz
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| posted on 14/2/10 at 03:41 PM |
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diagram
 
Rescued attachment cooling.jpg
ATB
Paul
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austin man
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| posted on 14/2/10 at 03:43 PM |
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Have you checked for an airlock in the system we had a problem on a zetec the airlock was near the temp sendor so not giving a correct reading, on
tickove all was okay but dropped when accelerating
Life is like a bowl of fruit, funny how all the weird looking ones are left alone
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prawnabie
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| posted on 14/2/10 at 03:45 PM |
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Are you sure you have the remote stat plumbed in correctly? I would say that the flow goes straight through the stat when its open, but it takes a 90
degree bend in yours?
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prawnabie
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| posted on 14/2/10 at 03:46 PM |
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Actually looking at it, you have the water entering the rad though the botom hose and exiting through the top??
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PaulBuz
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| posted on 14/2/10 at 03:46 PM |
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No defo. no air lock. The coolant sensor is directly in the coolant flow on the manifold I made.
ATB
Paul
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PaulBuz
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| posted on 14/2/10 at 03:52 PM |
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Yeah I know the rads back to front. Its real tight under the bonnet, so it was easier to plumb that way.
The stat. is plumbed correctly. it has a very big bypass, I think its the same as the K series mod. one.
ATB
Paul
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rachaeljf
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| posted on 14/2/10 at 05:16 PM |
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I've never seen a bypass thermostat go via the heater matrix. It would work as a simple on-off stat unless you have the heater on. The bypass
should go back to the pump inlet, but not via the heater.
Cheers R
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PaulBuz
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| posted on 14/2/10 at 05:23 PM |
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Have the heater on???
The heater is ALWAYS on. Its just sometimes you don't blow a fan thu it.
What difference will the restriction of the heater matrix make?
[Edited on 14/2/10 by PaulBuz]
ATB
Paul
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rachaeljf
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| posted on 14/2/10 at 05:47 PM |
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EACH to HIS own. Most cars with heaters have some means of turning off the coolant flow. It probably won't bother you in an open top car, but in
tin tops the heater can still cook you even with the fan turned off.
Since you have the heater matrix permanently on it won't bother the engine. However, once the engine's warmed up you won't have a
heater, whether you want it or not. That's how a bypass thermostat works, coolant flows through the rad OR straight back to the engine (via the
heater matrix in your case).
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PaulBuz
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| posted on 14/2/10 at 05:57 PM |
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Yes , I see your point.
The ony thing I can think of is that a bypass stat is normally fitted in the rad. return line.
BTW, I wasn't being funny with the capitals, but I've never seen a car where you could stop the flow thru. the heater matrix
edit to say .apart from my old mini!
[Edited on 14/2/10 by PaulBuz]
[Edited on 14/2/10 by PaulBuz]
ATB
Paul
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rusty nuts
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| posted on 14/2/10 at 06:04 PM |
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quote:
Originally posted by prawnabie
Actually looking at it, you have the water entering the rad though the botom hose and exiting through the top??
Seconded , Water is like air it will rise when hot and fall when cold.
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PaulBuz
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| posted on 14/2/10 at 06:21 PM |
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Yeah like I said I know its upside down.
If I had an overheating prob. I would change it over.
But I don't think its causing the underheating problem.
But I've been wrong before!
ATB
Paul
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snapper
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| posted on 14/2/10 at 06:28 PM |
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Over cooling is a good thing means you have plenty of capacity for the hot summers ahead.
Do what the racers do just tank tape over some of the rad, this way you can easily remove it in the summer
I eat to survive
I drink to forget
I breath to pi55 my ex wife off (and now my ex partner)
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PaulBuz
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| posted on 14/2/10 at 06:40 PM |
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But excessive overcooling causes engine wear
It should be simple.
the thermostat should maintain engine temp. regardless of ambient.
But it does'nt
ATB
Paul
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Bluemoon
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| posted on 14/2/10 at 06:52 PM |
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A lot of fords are plumbed like that with the heater always on. This includes my CVH doner Sierra! Has flaps to ensure no airflow when heater is
"off".
My fiesta has the same setup (with flow through the heater all the time well at least when moving anyhow). This would over cool on a long run when the
temperatures were low. Tested the stat in hot water all seemed o.k. On closer inspection there were witness marks on the wax stat where it had been
rubbing on the stat body (can't tell if this happen on removal as I didn't look before testing so it's possible I damaged it on
removal). Anyway replacing the stat fixed it. I guess sometimes the stat was getting stuck open a bit and hence the marks. Cheap enough to try a new
stat...
Dan
[Edited on 14/2/10 by Bluemoon]
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dlatch
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| posted on 15/2/10 at 12:48 AM |
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i think you are getting false temp readings prob due to how you plumbed top and bottom rad hoses
its actually more likely to be over heating
i would really swap them over asap and re test sure you will have a flow problem as the water is having to fight gravity to flow through the rad which
would also figure to the ok at idle but not when the engine is running higher revs.
plumbed the way you have it will also be much more likely to get airlocks as the pump will be sucking against the available water thats at the top of
the rad which is also where the air will be
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Bluemoon
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| posted on 15/2/10 at 09:09 AM |
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Tend to agree, the rad is plumbed in backwards.. Maynot be the problem, but I would re-plumb this..
Dan
quote:
Originally posted by dlatch
i think you are getting false temp readings prob due to how you plumbed top and bottom rad hoses
its actually more likely to be over heating
i would really swap them over asap and re test sure you will have a flow problem as the water is having to fight gravity to flow through the rad which
would also figure to the ok at idle but not when the engine is running higher revs.
plumbed the way you have it will also be much more likely to get airlocks as the pump will be sucking against the available water thats at the top of
the rad which is also where the air will be
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PaulBuz
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| posted on 15/2/10 at 09:32 AM |
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Good points.
TBH I had'nt really thought about the effects of pumping against gravity( which in turn I suppose could also cause cavitation & poor flow
not to mention the fact that if there is air in the rad. it will be at the top where the pump is trying to draw from.
I will replumb the rad ( areal PITA)
& report back.
Thanks to all for info
ATB
Paul
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thepest
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| posted on 15/2/10 at 11:37 AM |
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Use one of those IR temp sender guns, very usefull to see what temp is doing all around the engine and the cooling system. Also shouldn't your
water temp sender be in the flow out of the engine not on the in?
"Cold" water will always go into the engine after passing the rad. I believe its the temp coming out of the engine that you need to know.
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PaulBuz
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| posted on 15/2/10 at 12:38 PM |
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quote:
Originally posted by thepest
Use one of those IR temp sender guns, very usefull to see what temp is doing all around the engine and the cooling system. Also shouldn't your
water temp sender be in the flow out of the engine not on the in?
"Cold" water will always go into the engine after passing the rad. I believe its the temp coming out of the engine that you need to know.
The water temp sensor in directly in the flow out of the cylinder head.
Thats the fan switch you're looking at on the drawing.
ATB
Paul
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MikeRJ
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| posted on 15/2/10 at 01:36 PM |
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quote:
Originally posted by dlatch
you will have a flow problem as the water is having to fight gravit
Fighting natural convection, but not gravity. Not sure this will make a great deal of difference though, low temperature is most likely to be related
to the thermostat position and plumbing IMO,
Don't forget the Rover thermostat is a PRRT valve i.e. it opens under pressure as well as temperature. If something is causing an unusual
pressure drop across the thermostat under higher engine speeds it will open irrespective of engine temperarture.
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rachaeljf
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| posted on 15/2/10 at 04:37 PM |
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Paul, the thermosiphon effect is far weaker than the pump. Your "reverse" flow rad is not the problem.
Still think you need to re-do the thermostat plumbing though!
Cheers R
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britishtrident
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| posted on 15/2/10 at 07:34 PM |
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coolant circuit for external PRRT thermostat
[Edited on 15/2/10 by britishtrident]
 
Rescued attachment prt.JPG
[I] “ What use our work, Bennet, if we cannot care for those we love? .”
― From BBC TV/Amazon's Ripper Street.
[/I]
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PaulBuz
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| posted on 15/2/10 at 07:35 PM |
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Just come in from the garage.
I've worked out a pipe layout that is identical to the modified layout on the k seies using this stat.
http://web.tiscali.it/elise_s1/
Hopefully that should sort it out.
The best thing about this mod is that it reduces the thermal shock on the engine, & with the known head problems on this engine, that can only be
a good thing.
I'll report back my findings!
ATB
Paul
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