THE ROVER SD1 FORUM

Kassi · SD1 User Joined: 17 Feb 2007 Posts: 19

Hi,

after rebuilding an SD1 and fitting a 4L engine first I had to resolve problems with airlocks. Now I 'm quite sure no airlocks are in the cooling system anymore.
But cooling is very bad. Engine is running at different temperatures regarding the load and the outer temperatures. Driving at about 140 km/h at about 25°C, temperature is rising up to 95°C, then the electric van starts turning and then I go slowly.
The electric van (kenlowe 12") is in front of the radiator and could affect cooling when not running?
From the Rimmers I bought a new viscous van but is already broken again after 2000 km driving.
Possibly I need a more effective radiator, it seems to be not the first one and in principle in good condition. I have a new 75°C thermostate fitted and a new water pump.

Thank you for your help.
Christof

chris_derby · Posted: Wed Oct 03, 2007 10:12 am Post subject:

You have a kenlowe fan and the viscous fan fitted? Have you made sure that the fan blades are the right way around? the Kenlowe should be pushing the air & the viscous fan should be pulling. Have you flushed the cooling system out? You could have a blockage somewhere, or the thermostat could be faulty, maybe you should also test that?

ramon alban

Hello Kassi, Here are some observations in red

Kassi wrote:

after rebuilding an SD1 and fitting a 4L engine first I had to resolve problems with airlocks. Now I 'm quite sure no airlocks are in the cooling system anymore.

I have a personal process to eliminate airlocks in my Vitesse and would recommend it to you:

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But cooling is very bad. Engine is running at different temperatures regarding the load and the outer temperatures. Driving at about 140 km/h at about 25°C, temperature is rising up to 95°C, then the electric van starts turning and then I go slowly.

This smacks of airlocks still in the system possibly generating local hot spots and steam which will affect the temperature gauge sensor in the manifold giving a false "high" reading, but make no difference to the way the viscous reacts. Although I've never had electric cooling fan is it possible that the sensor for the fan may positioned and set in such a way as to prevent the viscous from ever operating.

The electric van (kenlowe 12") is in front of the radiator and could affect cooling when not running?

No, I think it may rotate freely in the airstream when moving.

From the Rimmers I bought a new viscous van but is already broken again after 2000 km driving.

The reason you may believe the Viscous fan is broken is that the engine temperature is generally not getting consistently high enough to make it operaste correctly. this link may help.

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Possibly I need a more effective radiator, it seems to be not the first one and in principle in good condition.

Original 3.5 rads had more pipes and cooling surfaces that other models so it may be the replacement rad is the wrong type.

I have a new 75°C thermostate fitted and a new water pump.

My understanding is that the optimum temperature for a 3.5 Engine is approximately 90 deg C. This is because of multiple references in the Rover SD1 Efi workshop manual regarding sensor measurements and running temperature and the option to fit 2 different thermostats 82 deg summer and 88 deg winter. Running a 75 degree stat in my opinion may be too low and will cause rich running, inefficient lubrication and excess wear. I do appreciate that you may not be running an Efi system.

_________________
Ramon

Kassi · SD1 User Joined: 17 Feb 2007 Posts: 19

- A viscous fan isn't fitted.
- Ratiator looks very original, with oil cooler for automatic.
- I cleaned the system already, no important residuous could be seen
- Electric fan is correctly fitted and is pushing through the radiator
- I have SU carbs fitted
- I used the 75°C thermostate due to beeing too hot with 82°C one

Air was thrown out at 4000rpm at stand, and then releasing throttle jerkly.

I hope this helps for further diagnosis.
Thank you so far.
Christof

ramon alban · Posted: Wed Oct 03, 2007 7:25 pm Post subject:

Kassi wrote:

Air was thrown out at 4000rpm at stand, and then releasing throttle jerkly.

But was WATER sucked back in its place or did the air just come out and be replaced by more air? My process ensure that water is sucked back.

Regarding thermostat choice I explained about hot spots and if you read the Rover workshop manual 3.5 specification the choice of stat is clear and does not include 75 deg.

It seems you are having to use a lower stat because the whole system is not functioning well enough to control the temperature. I believe that to be the wrong compromise.

_________________
Ramon

tim leech · Posted: Thu Oct 04, 2007 9:50 am Post subject:

I still think the viscous fan is the best Idea, yes a electric one will release a couple of horses but after having driven my car in very hot summer traffic more than once and seeing the temperature never go above 90 degrees Im happy with the original set up.

_________________
1979 Rover SD1 V8-S
1987 Rover 2600VDP Auto.
1985 Citroen BX 19GT
1990 Citroen BX 16v
1994 Citroen Xantia 1.8i SX

Kassi · SD1 User Joined: 17 Feb 2007 Posts: 19

Ramon,

I tried it as you described.
The problem is, that it's absolutely impossible to run the engine without the filler cap. The fluid level raises and fluid is getting pushed out.
Procedure begins again. No way so far.
I agree, air locks are the main problem. Second, as Tim said, I also believe that the viscous is very effective and is needed for good cooling. But It's very expensive, because my broken viscous fan I could only remove with an angle grinder. The Rimmers seem to have a quality problem with this part. Where can I get a good quality viscous coupling?
I will try the 82°C stat again next time. But not so important, because I don't drive in the winter. My car is sleeping already.
Cheers
Christof

ramon alban · Posted: Thu Oct 04, 2007 7:35 pm Post subject:

Kassi wrote:

Ramon,

I tried it as you described. The problem is, that it's absolutely impossible to run the engine without the filler cap. The fluid level raises and fluid is getting pushed out.

Procedure begins again. No way so far. I agree, air locks are the main problem.

What you are describing is exactly the heart of the problem. That air is trying to get out and is pushing the water out in front.

Dont worry, let it do so, but as soon as the burping stops and the water level starts to fall pour in some more coolant into the overflow tank and jam on the pressure cap. Lower the rpm and let it settle.

Check that the radiator is still full, if not just top it up and refit the bung.

Now remove the pressure cap, raise the revs, let the air do its stuff again, pushing out liquid and air until there is no more air. Let it ALL come out. Pour in more coolant and repeat until all the air has been expelled.

Providing the engine is not too hot you cant do any damage and if it does look like over heating then stop for a little while.

I promise you that it is the air that is causing the problem and when its gone so will the problem be gone too.

Think about it this way. Air expands more than water when heated, air spaces allow hot spots, hot spots generate steam. Expanded air and steam create great pressure, pressure sends the trapped air out of the system pushing the water in front of it.

Get rid of the air, no hot spots, no hot air, no steam, no problems.

Second, as Tim said, I also believe that the viscous is very effective and is needed for good cooling. But It's very expensive, because my broken viscous fan I could only remove with an angle grinder. The Rimmers seem to have a quality problem with this part. Where can I get a good quality viscous coupling?

Can you explain what happened to break the fan, how is it broken? is it physically damaged or does it just not lock up when hot?

I will try the 82°C stat again next time. But not so important, because I don't drive in the winter. My car is sleeping already.

Good luck

_________________
Ramon

Kassi · SD1 User Joined: 17 Feb 2007 Posts: 19

I bought a new viscous coupling from the Rimmers. Difficult to fit, because the fitting was too strong. But no problem so far. Then I never noticed any difference in moving regarding different temperatures. If engine was hot, nevertheless the load in turning the fan by hand was easy.
But after about 1000 km I found the fan sticking also when cold down. I could not turn the fan by hand. I tried it faster then the fan was turning again. After a short run the fan made a big noise like rattling. Observing it I found that the fan was wobbling. Absolute destroyed. Trying to remove the fan with an extractor, it was broken. The rest I had to remove with an angle grinder, the extractor was short before destroying, no chance to pull the flange off.

I got a discout from the Rimmers and I think they knew why.

Kind regards
Christof

ramon alban · Posted: Fri Oct 05, 2007 8:51 pm Post subject:

Kassi wrote:

I bought a new viscous coupling from the Rimmers.
I got a discout from the Rimmers and I think they knew why.

Christof,
Sorry, I did not realise it was kaput. Sounds like you have grounds for complaint, but not so easy from abroad. You could look into finding a substitute from another vehicle.

All one can really say is the system was designed to run with a viscous. Even so many people have success with electric fans on rover V8's too.

I'm not sure where that leaves your current situation but if you continue to have problems getting rid of air locks you may be able to bypass the fault by adding an extra overflow bottle as mentioned in the last paragraph of the article to take advantage of the suction that occurs when the engine cools down.

_________________
Ramon