Engine overheating

[BedfordStag]

Hi Guy's,

I need some help. I have a 75 Mk2 with a Rover 3.5 Rover engine fitted, apologies to the purists, it's not the engine I love its the styling... the car drove beautifully 3 months ago after spending about £8k sorting the underneath stuff out. The last two times I have taken it out it has overheated to the extent that the gauge is touching the red. I have run the engine a few time with the expansion cap removed watching for bubbles and topping up as necessary, it appeared that all the air had been removed, it made no difference to the temp.

My main question is, would the car overheat if the only fault was a stuck heater lever not allowing hot air in the car, would this mean no water is entering the heater matrix. I ask this as if the lever was in the cold position this surely would not cause the engine to overheat. A few people have said it's this which is the issue. there is no heat entering the car.

There also seems to be a bolt at the top of the radiator where the top hose is, is this some kind of bleed device? I haven't taken the thermostat out yet as it seems to reach a temp then the water leaves the expansion bottle which I assume is the thermostat opening. I do have an additional heat controlled fan fitted.

Just had another thought, if the thermostat wasn't opening would this also stop hot water going to the heater, is this a possible problem?

As you can tell I am no mechanic just trying to keep her on the road rather than be in the garage.

Any help would be really appreciated. I have never driven more than 15 miles as initially, it would break down, now all appears to be sorted and it overheats. Gutted.

[Kithmo]

Assuming you have the original radiator, the "bolt" at the top of the radiator is the filler plug, where you should be topping it up from.

[StagJonno]

The fact that water is being sucked from the expansion bottle as the car warms is the opposite of what I'd expect. Suspecting that you may have got an air lock. As Kithmo says, the correct filling point is the the "bolt" at the top of your rad. Have you been using the expansion bottle as your top-up point?

Suggest you remove the "bolt" and top up with coolant, then running the engine for a while with it off watching for air burps, topping up further as necessary. There are masonic-style techniques (lifting one corner or another) favoured by some to clear airlocks - not found necessary myself. Hopefully one of these guys will be along shortly to give more detail.

The heater is in circuit (assuming the lever is to Hot) from cold, so not directly impacted by the thermostat.

Jonno

PS - put the "bolt" back in (snugly, not overtight) before going for a run.

[Andy S]

Mine had some airlocks and can still hear a slight swirl in heater matrix suggesting still have air trapped.

However, make sure heater is on when topping up and park on steep slope with front as highest point. Run engine until thermostat opens and top up as coolant goes down. This should help get any air locks out.

The next day with top bolt still in and engine completely cold make sure expansion bottle is half full, adding or removing if necessary.

Andy S

[BedfordStag]

Kithmo - Jonno,

Really appreciate your help, thank you. I cannot believe I have been using the expansion tank as the filler, that seemed so logical. It may seem you provided simple advice but this could save me a small fortune, would have gone back to Robsports next week. Thanks again, guys. Have a great weekend.

[BedfordStag]

Thanks Andy

[Kithmo]

You're welcome, let us know the results

[StagJonno]

You're welcome - it's an easy mistake as usually on moderns, this is the procedure. Difference with the Stag is the expansion bottle level is below the top of the rad.

As Kithmo says, please keep us posted, especially if you're restored to happy Stagging.

Jonno


Jonno

[Phil S]

try a drop of washing up liquid in the rad..used a lot by plumbers to break down air locks in heating systems as it breaks the surface tension.
Phil

[Andy S]

Thanks Andy

Hopefully you’ll be able to enjoy a drive out tomorrow.

[mjheathcote]

try a drop of washing up liquid in the rad..used a lot by plumbers to break down air locks in heating systems as it breaks the surface tension.
Phil

I can understand the logic, but wouldn't, after using washing up liquid a few years ago in a dishwasher...
You want something non foaming!!

[Ian F]

Bedford Stag - did you also say the heater control lever is stuck? This won’t help when refilling the rad! As the guys have said, ideally fill with the heater ON and with the front nearside raised if possible. If your heater lever is stuck, search heater control valve on here, there is plenty of advice as to how to free this off, but you do need to be a contortionist.

ian F

[BedfordStag]

Here you go for stupidity, I had a mod by Robsport, they put a fan on with a sensor(temp I assume) so when the water temp gets to a certain heat the electric fan turns on.This means that if it's stationary surely the car will overheat as no wind is cooling the radiator. Am I right in saying a normal fan would be spinning as soon as the car is started?

[StagJonno]

That arrangement is fine - just like mine. You're correct in that the electric fan will be controlled by a thermostat - this means that it only runs when it's needed. It shouldn't promote overheating if your cooling system is operating OK. Engine and radiator flushed through so that coolant can properly circulate, and there's enough coolant. Some water loss might be tolerated, but if the level is below the level of the water pump (sits in the Vee, underneath the air filter/ inlet manifold), you'll be in trouble. From what you've described, I don't think yours is in that category.

Some owners reckon that the viscous fan (standard engine-driven) should be retained to keep general underbonnet temperatures down, though I've never found any issues and I know of several owners who have a similar arrangement. Just a word of caution, electric fans are not all equal. Therefore you need to be sure that they'll shift enough air to do the cooling effectively. Mine is a Kenlowe recommendation for the Stag and is capable of shifting 3740 m3/hour, which consumes 24A - this is on the high setting, though I normally run it on the "Normal" setting which only consumes 18A. I'm sure that, with their extensive Stag experience, Robsport will have supplied a suitable fan for your application, but if you've any doubt, contact them.

Jonno

[BedfordStag]

Well been at this all day, bloody cars!!!

Anyway put the car heater to hot, filled the radiator to max through filler plug/bolt, left plug off, checked level in the expansion tank, was low so topped that up, put the cap on and started her up. I got some air bubbles from the radiator plug, not much. Put the plug on and left her to cool down as she overheated.

Once cool took of the expansion cap and water down again, took off the radiator plug and topped radiator up, when I was filling noticed the level in the expansion tank went up. This time remembered to check all hoses, top hose very flexible but when I squeezed the bottom hose felt crusty inside, spent 10 minutes squeezing until it felt flexible like the top hose. Not sure what that was about. Started her up with the cap off and get a few more air bubbles out.

Let her go cold, topped up rad and halfway up expansion bottle, put the cap back on and started her up. Seemed to take longer to warm up, left her running and it did go over half way on temp gauge but not as hot as before. This time though the fan came on and the temp gauge dropped a little and fan cut off. That's a first normally the fan doesn't stop until 5 minutes after switching the car off. Appears to be better but still may be running a little hot. Didn't get to go for a drive will try tomorrow after checking levels. Fingers crossed.

Thanks for your comments again.