Loosing Coolant

Hi all. I've been trawling through all the threads I can find on this topic and think I have probably emptied the barrel of knowledge on it already, but, one more question:

How does the heater effect coolant temperature? To expand a bit, I have spent all morning running my engine 10P Td5 trying to locate the leak. I was running it at idle then revving it trying to get it up to normal running temp (by gauge). I had the heater on full blast and the cab was getting very toasty. But the gauge was only up about a quarter and no sign of a leak. So, quick drive around for a bit and still staying at around the quarter mark and driving lovely. I then decided to turn the heater off, hit the off switch and the temp gauge suddenly rose up to the halfway point!
So, can anybody explain to me what is happening? I thought that the coolant flowed through the heater matrix all the time and it was just the air blower that blew the hot air into the cab. Is there more to this and could it be the source of my coolant loss problem?

All (most :doh suggestions most gratefully received

Sounds like you have an airlock somewhere ...

check the level, when cool, re-fill if low ...

Make sure that the cap is fully tightened and let it run a bit with the bleed nipple out, u must have a clean/airless flow there..... refill the expansion tank if u loose much fluid while bleeding...

Is the rad hot all over ?

Dippypud said:

Sounds like you have an airlock somewhere ...

check the level, when cool, re-fill if low ...

Make sure that the cap is fully tightened and let it run a bit with the bleed nipple out, u must have a clean/airless flow there..... refill the expansion tank if u loose much fluid while bleeding...

Is the rad hot all over ?

Click to expand...

I have already checked and topped up coolant. I must admit, I have not felt the radiator(s) - not with that big fan spinning!

I've had problems with this for a couple of months but thought It was just a leak. The worry is when you're driving along and suddenly you lose power and the temp gauge moves up to the red. This happened and I pulled over, let it cool down then topped up with water. It was ok then until one day it happened again, but when I opened the bonnet, water was spouting out of the expansion tank. I thought I'd not tightened the cap properly as it was loose and boiling water was coming out. After cooling, topping-up and tightening the cap, it all seemed fine again. A couple of weeks later, I noticed the symptoms appearing again: first the heater does not warm up for a good 20mins then when it did, gauge flew up to red zone, lost power and limped to side of the road. Checked and coolant was low again. Topped-up and off we went, however, the power was now down. Low revs power was definitely down and it was struggling to accelerate under load.
I did a lot of researching this issue on LZ and other places and quickly realized this is a common problem and that I probably had a blown head gasket or worse, a crack somewhere (no sniggering), so I decided to try and eliminate a few things before looking at the head. I would point out that there is no sign of oil contamination of the coolant or visa versa.
First I thought I'd have a seriously good look for the leak. That's what I was doing today but didn't find it, just another question (or clue?) I really am curious why turning off the heater blower would cause the temp gauge to rise so sharply? Was it really taking that much heat out of the coolant?

Tomorrow I plan to drain the coolant and replace it. Bleed the system, and replace the expansion tank cap with a new one.

As far as the head goes, I can see no sign of a visible problem. It's not easy to see much mind even with the cover and cowl off. There is obviously a problem somewhere as the coolant must be going somewhere. There is water/coolant on the crossmember below the bell-housing and I would assume this is it, but cant see where it's come from. I thought that could be drainage from heater/aircon?

take off the the fan top cover, turn the engine off and feel the rad all over, make sure it is warm all over, mine was only getting warm top right corner as you look at it from the front, so i replaced thermostat and new good quality rad and expansion cap, flushed system and has been ok since, but i didn't have the symptoms as bad as your having, but was worried it could be head gasket, is bleed system properly

Have you done a sniff test on the header bottle for exhaust fumes not every HG prob means oil water mix . And if you shut off heater it does restrict the water flow . But as said above I would 1st have a good check of rad and thermostat . And when refilling add the new coolant slowly

Waterpumps leak internaly.also check fuel cooler.whilst you have it drained and for what it cost fit a new water pump.all new hose clips and think about new rad.mine used to drop an inch in header tank so i did all above been fine since.

Vanmancan said:

Have you done a sniff test on the header bottle for exhaust fumes not every HG prob means oil water mix . And if you shut off heater it does restrict the water flow . But as said above I would 1st have a good check of rad and thermostat . And when refilling add the new coolant slowly

Click to expand...

Are you absolutely sure about that? I was of the opinion that the coolant/heating circuit remains the same - completely open - irrespective of the heater position selections.

The cabin heating and ventilation system merely affects the air-flow via or by-passes the heater matrix.

So irrespective of heater controls, the coolant flows through the heater matrix.


Dave

thebiglad said:

Are you absolutely sure about that? I was of the opinion that the coolant/heating circuit remains the same - completely open - irrespective of the heater position selections.

The cabin heating and ventilation system merely affects the air-flow via or by-passes the heater matrix.

So irrespective of heater controls, the coolant flows through the heater matrix.


Dave

Click to expand...

I will check on it . Soz if I got it wrong . Was always shaw it stems flow when set to cold . Hence why when you have a air lock and open the heating you can often here the air bubbles gurgling round .

Vanmancan said:

I will check on it . Soz if I got it wrong . Was always shaw it stems flow when set to cold . Hence why when you have a air lock and open the heating you can often here the air bubbles gurgling round .

Click to expand...

I think you find it hasn't worked like that since before DI.

Dave

Clearly my age is showing :-/ I did go through collage in the 80s and there's only so much you can learn working on a mini metro . Think a read up on rave is in order at coffee break time.

Vanmancan said:

Clearly my age is showing :-/ I did go through collage in the 80s and there's only so much you can learn working on a mini metro . Think a read up on rave is in order at coffee break time.

Click to expand...

I'm not saying you're wrong mate honestly, maybe thing have just moved on a bit that's all. And there's alway a good chance I'm wrong !!!!!!!!!


Dave

thebiglad said:

I'm not saying you're wrong mate honestly, maybe thing have just moved on a bit that's all. And there's alway a good chance I'm wrong !!!!!!!!!


Dave

Click to expand...

No m8 . You prob called it right . Happy to be wrong

Paul

Well had a read and I was wrong in saying the heating is bypassed . There seem to be a bypass but as it's not a stand alone part looks like it's all I with thermostat. Found this on rave :
Thermostat - Main valve
The thermostat is used to maintain the coolant at the optimum temperature for efficient combustion and to aid engine warm-up. The thermostat is closed at temperatures below approximately 82°C (179°F). When the coolant temperature reaches approximately 82°C the thermostat starts to open and is fully open at approximately 96°C (204°F). In this condition the full flow of coolant is directed through the radiator.
The thermostat is exposed to 90% hot coolant from the engine on one side and 10% cold coolant returning from the radiator bottom hose on the other side.
Hot coolant from the engine passes from the by-pass pipe through four sensing holes in the flow valve into a tube surrounding 90% of the thermostat sensitive area. Cold coolant returning from the engine, cooled by the radiator, conducts through 10% of the sensitive area.
In cold ambient temperatures, the engine temperature is raised by approximately 10°C (50°F) to compensate for the heat loss of 10% exposure to the cold coolant returning from the bottom hose.
By-pass flow valve
The by-pass flow valve is held closed by a light spring. It operates to further aid heater warm-up. When the main valve is closed and the engine speed is at idle, the coolant pump does not produce sufficient flow and pressure to open the valve. In this condition the valve prevents coolant circulating through the by-pass circuit and forces the coolant through the heater matrix only. This provides a higher flow of coolant through the heater matrix to improve passenger comfort in cold conditions.
When the engine speed increases above idle the coolant pump produces a greater flow and pressure than the heater circuit can take. The pressure acts on the flow valve and overcomes the valve spring pressure, opening the valve and limiting the pressure in the heater circuit. The valve modulates to provide maximum coolant flow through the heater matrix and yet allowing excess coolant to flow into the by-pass circuit to provide the engine's cooling needs at higher engine rev/min.

cambridgecockney said:

Waterpumps leak internaly.also check fuel cooler.whilst you have it drained and for what it cost fit a new water pump.all new hose clips and think about new rad.mine used to drop an inch in header tank so i did all above been fine since.

Click to expand...

My money would be on a blocked rad or knackered water pump or stat too

quick update. I've drained the coolant, flushed the rad, re-filled. fitted new drain washer and expansion tank cap. Bled the system and topped up. went for a drive and all seemed to work fine and no power loss issues. I'll see how this goes as I'm sure I do have a leak somewhere. Rad looks fine.

And the thermostat? you didn't mention you had changed it!

Two possibilities ( I've experienced both ) for a leak at the bellhousing end are :
1) oil cooler and
2) a plug in the head inside the exhaust manifold .
When I took off the oil cooler the gasket had practically worn away in one section - new gasket sorted it .
The plug inside the exhaust manifold was more troublesome :
* remove exhaust manifold ;
*unscrew plug using Allen key ;
* had a problem when unscrewing plug - the part of the plug inside the
head was corroded , threads in poor condition resulting in damaged
threads in the head ; just about managed to clean them up

discodrivercumbria said:

And the thermostat? you didn't mention you had changed it!

Click to expand...

No, I hadn't ordered one, so not changed. However, when I did my test drive I watched the sequence of events as they unfolded:
Engine cold, temp gauge on cold, heater blowing cold
Engine warming, temp gauge cold, heater blowing warm
Engine warmer, temp gauge cold, heater much warmer
Engine warmer, temp gauge, moved up to quarter, blower getting hotter
Engine warm, temp gauge halfway, blower hot

This fits with thermostat opening at temp and thus allowing water to flow out over the coolant temperature sensor and thus the gauge moving up in the 2 stages observed.

Since I had lost coolant and had been topping up without raising tank or opening bleed valve, I'm sure I had allowed air into the system. This would account for a lot of the earlier probs. Having drained and re-filled properly this time, I am much more confident that the system is working correctly. However, I don't know what happened to the original coolant that went missing but it must have gone somewhere. It could be that the cap affected the temperature and caused a boil over loss, but I reckon I have a leak.
The rad looks dry and corrosion free, the hoses look good, but I wonder about the pump or a core plug. I can't really see with the turbo etc in the way so I guess I'm going to have to take that off and have a closer look. I'll wait first and see how much coolant I now loose and how quickly.

I still hope the head/block are ok.

dooroy said:

Two possibilities ( I've experienced both ) for a leak at the bellhousing end are :
1) oil cooler and
2) a plug in the head inside the exhaust manifold .
When I took off the oil cooler the gasket had practically worn away in one section - new gasket sorted it .
The plug inside the exhaust manifold was more troublesome :
* remove exhaust manifold ;
*unscrew plug using Allen key ;
* had a problem when unscrewing plug - the part of the plug inside the
head was corroded , threads in poor condition resulting in damaged
threads in the head ; just about managed to clean them up

Click to expand...

That's interesting. I'll have to investigate this when I get stuck into mine. Thanks for the pointer

well lets hope you are nearer! when it's upto temp is rad hot all over, ie down near thermostat, which rad is it, mine was the 1 with 2 pipes at the thermostat end PCC00150 new part no (PDK000080) just wasnt getting hot all over, new stat and rad, cap been ok since