Advice on oil coolers please

[Stag About Town]

Still trying to resolve the heavy thumps and clonks engaging forward or reverse on my type 65 auto. This does not happen when the gearbox is cold but gets worse as the gearbox gets hotter. I am thinking now maybe it is to do with the oil cooler? Mine is looking pretty tatty so I think I will change it anyway but in the meantime I notice the cowl bolted on to the bottom of the radiator frame looks perfectly positioned to prevent air flow to the oil cooler? What is the purpose of the cowl and would it cause problems if I took it off, maybe cause an issue with the fan or something. Has anyone removed it and if so did it cause a problem?

Many thanks

John

[markmark2]

Still trying to resolve the heavy thumps and clonks engaging forward or reverse on my type 65 auto. This does not happen when the gearbox is cold but gets worse as the gearbox gets hotter. I am thinking now maybe it is to do with the oil cooler? Mine is looking pretty tatty so I think I will change it anyway but in the meantime I notice the cowl bolted on to the bottom of the radiator frame looks perfectly positioned to prevent air flow to the oil cooler? What is the purpose of the cowl and would it cause problems if I took it off, maybe cause an issue with the fan or something. Has anyone removed it and if so did it cause a problem?

Many thanks

John

The purpose as far as I can see to to protect the fan as it is lower than the valence. Without it any obstruction would damaged the fan then possibly the rad/cooler. I removed the rad and forgot to refit the cowl and noticed it. The clonking gearbox is normal. My car is set to tickover at 500 in drive, think thats as good as it gets. I may be wrong. Mark

[Lingen]

John.
I would advise that you leave the fan cowl in place. A stag owner I know didn't even know his car was supposed to have one, and the fan picked up some polythene sheet of the road. Fortunately the radiator survived, but he has now bought and fitted one.
Mike.

[Stag About Town]

John.
I would advise that you leave the fan cowl in place. A stag owner I know didn't even know his car was supposed to have one, and the fan picked up some polythene sheet of the road. Fortunately the radiator survived, but he has now bought and fitted one.
Mike.

Mike. Thanks for that, I did think it was there to protect the fan but it does seem strange to position the oil cooler that needs air flow directly behind the cowl that seems to limit air flow to the ends of the cooler only? Seems an odd design feature. If the engine fan was constant it would probably provide the air flow but of course when the fan turns, the gearbox is not normally working if the car is stationary, but and when in motion and the gearbox working, the fan stops. At least that is my limited understanding. Maybe a grill set into the cowl or a line of holes in line with the cooler might help. I am only looking at this because my gearbox "clonks" from N to D and R do not happen when the gearbox is cold, even on higher choke revs, but get worse as the car gets hotter. Could be a wild goose chase but I thought it worth checking out.
Regards
John

[DJT]

John,

I would say that you have a problem not related to the cooler, unless it is blocked. I suspect that all the fins are flattened. Half an hour with a small screwdriver will straighten them out and improve the cooling. FWIW I have a standard radiator, OE fan and run a ZF through the OE cooler.

[mallardstag]

Have you checked the gearbox fluid level?

Changes from cold to running temperature are normal as the gearbox fluid getting less viscous as it warms up. It's unlikely that the oil cooler is causing this problem. What is the idle RPM hot and cold? As DJT says unless the cooler is leaking just straighten out the fins and wash clean between the fins with a pressure washer.

[Stag About Town]

Have you checked the gearbox fluid level?

Changes from cold to running temperature are normal as the gearbox fluid getting less viscous as it warms up. It's unlikely that the oil cooler is causing this problem. What is the idle RPM hot and cold? As DJT says unless the cooler is leaking just straighten out the fins and wash clean between the fins with a pressure washer.

Fluid level is ok. The idle is about 1500 on choke when there is almost no thump. About 600 / 700 on idle when hot in neutral, a bit less in drive. Will take advice from you and DJT on cleaning and sorting out the fins. Thanks both John

[mallardstag]

Fluid level is ok. The idle is about 1500 on choke when there is almost no thump. About 600 / 700 on idle when hot in neutral, a bit less in drive. Will take advice from you and DJT on cleaning and sorting out the fins. Thanks both John

Try reducing idle RPM to 500 when warm and about 900 on choke. This should reduce the 'clonk' when selecting a gear. Also check for play in the propshaft, diff and drive shaft joints which will make it sound worse. Some 'clonk' is normal.

[Stag About Town]

Try reducing idle RPM to 500 when warm and about 900 on choke. This should reduce the 'clonk' when selecting a gear. Also check for play in the propshaft, diff and drive shaft joints which will make it sound worse. Some 'clonk' is normal.

No more adjustment on the throttle stops. Any way I can get the revs down a little more?
John

[dickr]

on my 76 auto, a previous owner extended the pipework and moved the gearbox oil cooler to the lower front of the rad, fixed with the normal type of plastic pins. This does not seem to have affected the engine cooling at all and presumably improves the gearbox cooling. As to clunks, it's usually the drivetrain, the diff oil thins as it warms which would contribute to noises, also grease in the u/js would warm up as well.

[Lingen]

John.
I think you may be misunderstanding the operation of the engine driven fan. It operates continuously, but the viscous coupling "Slips" when the engine reaches around 2000 rpm, stabilising the fan at that speed. The only time it stops is when you turn the engine off. The cowl may restrict the air flow to the cooler a bit, but on the move, there is more than enough air blowing about down there to cool it.
Mike.

[markmark2]

No more adjustment on the throttle stops. Any way I can get the revs down a little more?
John

Hi John, I would disconnect the linkages and adj accordingly. Sounds like not set up correctly, which in turn could affect your gear changes, not clonks. Ask me how I know...Mark

[Stag About Town]

Hi John, I would disconnect the linkages and adj accordingly. Sounds like not set up correctly, which in turn could affect your gear changes, not clonks. Ask me how I know...Mark

Thanks for that Mark. Something else to look at.
John

[Stag About Town]

John.
I think you may be misunderstanding the operation of the engine driven fan. It operates continuously, but the viscous coupling "Slips" when the engine reaches around 2000 rpm, stabilising the fan at that speed. The only time it stops is when you turn the engine off. The cowl may restrict the air flow to the cooler a bit, but on the move, there is more than enough air blowing about down there to cool it.
Mike.

Thanks Mike. You are correct, I was under the wrong impression about the fan operation. Glad I asked the question though.
John