coolant problems

[dave wj]

Hi Guys,

Apologies if this has been covered before, but this is driving me nuts;

Got a 4.6 RV8 in my kit car about a year old (SD1 front cover, edelbrock 500 carb, no heater). Had an issue last year , it overheated due to fan thermostat switch failing. Also had to replace water pump around the same time.

Since then I've never managed to get the coolant levels to remain stable.
Initially, every time I went on a short run, the level in the exp tank would drop so I'd have to add coolant.
Now I'm finding the opposite, after short runs especially if I give the engine some welly, I check the coolant level when the engine is cold and every time it seems to have gained coolant. It's getting close to filling the exp tank. had to remove some to stop this happening.
The engine does not overheat .
I've done the usual to try to check for air locks, jacked the front of the car up and ran with cap off to wait for expected air.
Curiously the level starts to rise within a minute or so of starting the engine and is overflowing before the thermostat is open ( stat housing has bypass spiggot, hose plumbed into back of waterpump). No bubbles at this stage. I dare not carry on for fear of draining excessive coolant and causing damage. Should I keep going to see if any air eventually comes out?
I'm starting to wonder if the earlier overheat caused a head gasket failure. Tried to use the gas detector to check for emissions in the coolant, but sadly the exp tank overflowed before anything showed (no bubbles in the coolant anyway)

Thermostat has the little hole in it to allow for passage of air when filling coolant.

Before I start pulling the heads, is there a foolproof way I can be absolutely sure there are no airlocks in the system.

Sorry about the length of the post, I.ve tried to give you as much info as possible.

Thanks for your help

Cheers

dave

[ramon alban]

Dave, try the link to be found on this page.

http://www.vintagemodelairplane.com/pag ... cks01.html

[ChrisJC]

So is the heater circuit just a loop?, or blanked off? I'm not sure about this, but I wonder:
If you blank off the heater circuit so no water can flow, does that mean that no water flows until the 'stat is open?

Chris.

[dave wj]

So is the heater circuit just a loop?, or blanked off? I'm not sure about this, but I wonder:
If you blank off the heater circuit so no water can flow, does that mean that no water flows until the 'stat is open?

Chris.

I have a hose from the rear of the water pump connected to the rear of the inlet manifold (a heater would normally be in this loop). The other connection from the back of the pump is connected to the thermostat housing. Iam not sure but I believe this allows for circulation of water around the engine before the stat opens, eventually allowing water to rad.

filling the system, I have done by the book. The continuous rise of the coolant would suggest pressurisation of the coolant by either airlock or failed head gasket.
Do I keep running the engine and hope for the elusive bubble (assuming it is an airlock) bearing in mind I'm losing coolant at a pretty alarming rate out of the exp tank. (the more revs I give it the faster the loss)

Ramon, thanks for the link very useful. I would add all the cooling components are only about a year old as is the engine, so blocked cooling channels etc wouldn't be a problem.

This is doing my head in.

Cheers guys

Dave.

[ramon alban]

Do I keep running the engine and hope for the elusive bubble (assuming it is an airlock) bearing in mind I'm losing coolant at a pretty alarming rate out of the exp tank. (the more revs I give it the faster the loss)

Dave.

Yes! It just the air trying to get out, just follow the process described, raising and lowering the revs and pouring in more coolant, check the rad remains full all the time.

You can catch lost coolant in a big tray, if its dirty, filter and reuse it.

[dave wj]

Do I keep running the engine and hope for the elusive bubble (assuming it is an airlock) bearing in mind I'm losing coolant at a pretty alarming rate out of the exp tank. (the more revs I give it the faster the loss)

Dave.

Yes! It just the air trying to get out, just follow the process described, raising and lowering the revs and pouring in more coolant, check the rad remains full all the time.

You can catch lost coolant in a big tray, if its dirty, filter and reuse it.

Thanks Ramon,

One thing I didn't make clear is that the top of the rad is lower than the top of the engine (has to be in my kit car), therefore the exp tank has to be at the highest point above the engine. The pressure cap is on the exp bottle. The Rad has a non pressure cap so in effect is a sealed unit. With this setup I have to rely on the exp tank for visual coolant level check. If I try to open the rad cap, coolant just pours out and of course empties the exp tank in the process. I guess what Iam hinting at is that it is not possible to check the radiator level once the exp tank is full, however the top rad hose is connected to a smaller hose which in turn is fitted to a small outlet on the top shoulder of the exp tank, any air in the rad should escape via this hose thus allowing the rad to fill (hopefully). Hope this makes sense.

Apologies if I seem a bit dense in this area, but I've been struggling with this problem for months without success.

Thanks again for your help.

Cheers

Dave

[Ian Anderson]

Jack up the front of the car and put in axle stands

Then bleed it

The radiator should then be above the height of the engine

We have the same problem with the GT40s but then we also have 8 foot of pipe fron the engine to the rad and back

This will also allow any trapped bubbles in the engine to moveand possibly escaps

Ian

[ChrisJC]

I'd let the expansion tank spit out as much as it wants to, then I expect it will suck loads of water in, so be ready with a big jug of it!

Chris.

[dave wj]

Jack up the front of the car and put in axle stands

Then bleed it

The radiator should then be above the height of the engine

We have the same problem with the GT40s but then we also have 8 foot of pipe fron the engine to the rad and back

This will also allow any trapped bubbles in the engine to moveand possibly escaps

Ian

Thanks Ian,

Thats the next thing to try, I started to do just that at the weekend ,then the heavens opened. Never got the car off jacks and back in the garage so quickly ( open top, everything drenched) and to think I built this car for a bit of fun.

Cheers

Dave

[dave wj]

I'd let the expansion tank spit out as much as it wants to, then I expect it will suck loads of water in, so be ready with a big jug of it!

Chris.

Thanks Chris, Judging by the speed at which the water rises and puthers out, I reckon a watering can will be handy.

Sheesh this is going to be fun!

Cheers

Dave

[ian.stewart]

Did you ever have issues with the level before you fitted the new stat and pump, I am wondering if the new pump is more efficient than the old one and playing with you, Can you fit a larger expansion tank on just to eliminate the pump theory?? and before the fan probs, were you so conscious of the water level fluctuating,
You also say is there a check that you can do for a head gasket or liner leak, yes, you can take the car down to your local friendly garage and ask them to do a Hydrocarbons test on the water system, no hydrocarbons, no compression leaking into the water,

[dave wj]

Did you ever have issues with the level before you fitted the new stat and pump, I am wondering if the new pump is more efficient than the old one and playing with you, Can you fit a larger expansion tank on just to eliminate the pump theory?? and before the fan probs, were you so conscious of the water level fluctuating,
You also say is there a check that you can do for a head gasket or liner leak, yes, you can take the car down to your local friendly garage and ask them to do a Hydrocarbons test on the water system, no hydrocarbons, no compression leaking into the water,

Hi Ian,
Sadly it was not long after the new engine went in that I had a boil up as mentioned in my first post so I didn't do enough miles to know if the coolant was playing up or not, the new water pump went in shortly afterwards. Its over the past seven or eight hundred miles since these episodes where the coolant levels have been all over the place.
Initially coolant was being lost. This made me think that maybe I had cracked a liner or block during the overheat (no visible leaks and worst when accelerating hard).
I did as you suggested and contacted my local garage for a hydrocarbon test but owing to the coolant being pushed out of the exp tank at a great rate of knots this didn't work.
Recently, instead of losing coolant (ie constantly topping up the level after a run), its gone the other way with coolant levels rising. I check when the engine is cold and after each run I find the level has risen compared to the previous measurement. As I mentioned, the exp tank is now almost full to the point where Iam going to have to empty it. This makes me think that either air from an air lock (after this many miles???) or emissions from blown head gasket causing an air lock is causing the coolant level to show higher after each run. Even if I remove the excess coolant from the exp tank, it is still higher next time I check after a run when cool.

I have just got a larger exp tank from the scrapper which I may try, but am not convinced this is the whole problem.

Is it possible to drive for upto a thousand miles with an air lock and yet have no overheating probs and on the face of it the airlock not escape of its own accord eventually...mine doesn't appear to have(assuming it is an air lock).

Please let me know what you think about the above. I'm sort of chasing my tail over this a bit.

Many thanks for your help.

Cheers

dave

[ChrisJC]

I have a Rover SD1 expansion tank on my 4.6 Landie, and it's only marginally large enough. In fact, it probably isn't large enough to cover all extremes of operating.

Chris.

[dave wj]

I have a Rover SD1 expansion tank on my 4.6 Landie, and it's only marginally large enough. In fact, it probably isn't large enough to cover all extremes of operating.

Chris.

Hi Chris,

Any idea on the volume of your exp tank? The total capacity of mine is 1.1 ltrs.
I'm starting to think it is way too small.

Cheers

Dave

[dave wj]

Now this is weird!

You know I've been telling you my coolant has been rising recently, well:

Went for a blat last night, probably about 15 miles.
Checked my coolant this morning and would you believe there is significantly LESS in the exp tank than when I started last night.

I don't get it, the last few times I check it when cold, it has risen every time. Now its on its way down. If it continues this trend, there will be nothing in the exp tank after the next run and who knows, may well start rising again in a few runs time. Its up and down like a yo yo.

Can anybody make any sense of this?...........please!!

After my hols I shall be fitting a larger exp tank to see what happens.

This is just insane!

Thanks for your help guys

Cheers

Dave