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]

diagram
Rescued attachment cooling.jpg

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

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?

Actually looking at it, you have the water entering the rad though the botom hose and exiting through the top??

No defo. no air lock. The coolant sensor is directly in the coolant flow on the manifold I made.

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.

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

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]

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).

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]

quote:

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Originally posted by prawnabie
Actually looking at it, you have the water entering the rad though the botom hose and exiting through the top??

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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!

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

But excessive overcooling causes engine wear
It should be simple.
the thermostat should maintain engine temp. regardless of ambient.
But it does'nt

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]

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

Tend to agree, the rad is plumbed in backwards.. Maynot be the problem, but I would re-plumb this..

Dan

quote:

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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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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

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.

quote:

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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.

---

quote:

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Originally posted by dlatch
you will have a flow problem as the water is having to fight gravit

---

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

coolant circuit for external PRRT thermostat

[Edited on 15/2/10 by britishtrident]
Rescued attachment prt.JPG

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!

Hmm, the very last diagram makes sense. The heater matrix is not involved with the bypass circuit. As I said before, with your current layout once your engine is properly warmed up you won't have a heater.

And I note the last line: "Also worth mentioning, on the Lotus Elise, the possibility to close the heater circuit with a valve (very useful during the hot summer months) without significantly reducing the overall bypass flow."

Cheers R