Changing a Type 4 Oil Cooler

[Pabloako]

Hi everyone,

I am still fighting a cooling issue and the oil temperature getting over 120 celsius in my Type 4, 1800cc engine, so I have purchased a new oil cooler, which arrived today.
Does anyone know if replacing the cooler is major surgery, or can I just remove the cooking fan and tinware?

Many thanks

Paul

[Mordred]

Major surgery?  Depends on your definition, but it is a bit more complex than you may think. It can be done in the car, but it is way easier engine out.  There a few things that might make it harder.  

BTW When you fit the new cooler make sure you follow the torque settings which are extremely light and you can't do them with a normal torque wrench as it isn't accurate down that far.  The upside is you can use the smaller one for the sump plate nut and a few other things if you go to buy one, so it isn't a one off purchase.

First is going to be the heater boxes. there are little covers that you can remove where the air bleed from the cooling fan is connected at the bottom of the housing, but you will have to cut and bend the tin on rear side the heater box where the fan housing outlet is (just a single cut down with tinsnips and bend it towards you, then bend back when you refit) to free it without taking off the exhaust and heater boxes.  Reason being the fan housing has to come back to clear the mounting studs and the top engine tin and also up to clear the heater boxes.

Second, you have to disconnect the alternator connections from the starter motor and regulator and feed the cable through the tin ware or remove the alternator altogether (remember to release the rubber boot at the back of the alternator with a phillips head screw driver from below before trying to take the alternator out). as it is attached to the cooling housing.

Third, and most painful really, the oil dipstick tube has a rubber bellows on it that joins the tube through the housing to the engine case, quite fragile and it will probably leak if it isn't now. Bugger to get back on too. Get a new one made of Viton before you start and then just replace it.

They are the things I can think of off the top of my head.

Then while you have it all apart, look sat the top of the cylinders and heads under the tin on both sides and see if they are clean and free of grease dirt leaves etc. Is the existing cooler clogged up with rubbish. (amazingly common)  Make sure the flaps are there and working.  Even without a thermostat to operate them they will sit in the warm position and are important for air flow.

Before you go down that track here is a few things that can affect your temps.

1. Checked all the tin is in place
2. The engine seal is in good condition
3. Timing is correct, and engine tuned, valve clearances correct
4. Engine case relatively clean and not covered in grease and dirt.
5. Using the correct oil in hot weather.  A slightly lighter oil may help as heavy oil increases oil pressure and may operate the bypass valve which reduces the oil going through the cooler.
6. Carbs and distributor the correct ones for the engine (1800 has a 205P Dizzy (last 3 digits stamped on the side) with vac advance and Carbs with a number 4xx stamped under the float bowls. (hard to do without a camera on a phone 3xx is 1700 and 5xx is 2l) and in good condition. 
7. 1800 engine with a 002 gearbox is happiest around 90-100 kmh, you might be pushing her a little hard on a hot day at 110kph if that is where you are seeing the overheating issue.

not an extensive list but all could be contributing to your issues.

good luck

Adrian

[Pabloako]

Amazing information Adrian, thank you.
What is quite frustrating is that I replaced the alternator and the dipstick bellows not long ago and had it half apart then.  Such is life.

I live in a very hilly area and I think my main problem is that she isn't cooling down after getting hot.  Down hill she is around 100C, on the flat around 110C and going up hill she gets to just over 120C.  If going up hill and then on a long flat, the temperate doesn't go down again.  The only way I can get the temp to drop is pull over, turn her off and brew a cup of tea and wait.

Also a big thank you for the 7 bullet points too.  #5 would be something for me to test.

[Pabloako]

Hi Adrian,

Once again a huge thank you for the detailed instructions. So far it is progressing suprisingly well, which with my bus, is a very rare occurrence. No doubt there will be a surprise soon. 

I am up to snipping the heater box to bent the small section out of the way and in the process of dismantling things, I found one small cover where the bleed air enters the heater box under the alternator is missing, which explains the small puff of air I am receiving in the cabin.  It is a pretty small piece, so I will have a go at making one.

Thanks for suggesting snipping a bit of the heater box. I wouldn't have been game enough to do it without you suggesting it.  Bend it back together, weld it up and no one will ever know! 

[Pabloako]

Still going well and I am almost in shock!

Here is the oil filter in all her gummed up with 50 years of crud glory.

A bit of cleanup need needed and I haven't taken the two parts of the fan shroud apart yet, to see what slimy stuff is inside that.

Should I expect the old cooler to be full of oil?  There is a dribble in there, but that is about it.

[Barry]

Pabloako
Do yourself a favour and loose the see through dizzy cap. 
That could be part of the problem. 
The quality is so poor it is probably misfiring

[Pabloako]

Hey Barry, thanks for that. I have never liked that cap, because the clips are so tight on it, they almost break my fingers trying to get them on.

I have just ordered a Bosch one from JK.

[Pabloako]

The new cooler is in and I took her for a drive up the hill (21km up) last weekend and she still got very hot (over 130C), however she did cool down again on the flat, so that was an improvement.

The new dizzy cap arrived yesterday, so i popped it on today and I just took her up the hill again and she didn't get above 110C.   She then cooled back down to 100C on the flat.
I reckon I owe you a beer Barry!

I will give her a tune up tomorrow.

[Mordred]

Glad you have started to move forward sorting it. I have seen oil coolers blocked up a lot worse and still not causing too much of a concern, but it is definitely a good start. I would check the timing now you have a new cap, that old one seems to have been a factor.

Don’t get too fixated on the temp on the gauge, use it more a guide to what is normal and what isn’t, but regardless 130 after 20km is a red flag, especially if you are going hard. Other things that can contribute are poor mixture(lean), advanced or retarded timing, poor fuel quality( tends to cause other issues including rough running) worn or wrong carbs, worn or wrong distributor, etc. 

They are relatively simple engines but 50 years of people fiddling and mechanics who think they know better than the engineers who designed them contribute, and variable quality aftermarket replacement parts can all contribute to things not being quite right.

A good example is there are a ridiculous amount of variants of the original solex twin carbs that all look basically the same, but they have to be a matched set to each other and also to the engine, distributor and even gearbox. Auto and manual, plus different levels of emission control equipment, 1700, 1800 and 2l and year and market sold in. One side stuffs up and someone has a similar in an old engine so wack it on and it will work closely enough but never quite right, then add a few other adjustments and aftermarket parts and things continue going down hill.

Anyway, looks like you are on the right track, get out an enjoy it.

Adrian

[Pabloako]

Quick update on my on going cooling issues.  Whilst cruising 85-90kmph I am still getting oil temps up to and slightly over 120C and the oil pressure was still sitting above 2.5 Bar.   I have changed the cooler, set the valves, set the timing, all tin is there and all engine seal (foam stuff) is there.  I have experimented with 10/40 oil and 10/30 oil, plus experimented with 91 and 98 fuel.

I found that once she got hot (over 120C) the only way to get her to cool down was to either stop for 10 mins, get to a T junction and let her idle for a few minutes of enter a town and slow down for traffic lights and crossings etc.

On my latest oil change, I unscrewed the oil pressure valve screw by the oil filter and found that the plunger part of the valve had been installed upside down by previous owners, with the flat part touching the spring and not the recessed side, so the groove was at the bottom.  Bentley has it the other way around.  I reckon I may have had very little oil going in to the cooler.



This may be something to check if you have similar cooling issues.  Anyway, I will let you know what difference it makes.