Hi Gary.

Or just drill about 3 or 4 6mm holes around the edge of the flat piece of the stat, you will get flow all of the time and stat control when needed.

Tim

Other then internal heating what is the main issue with running without the stat?

That housing can be quite brittle and fragile so for me I didn't want to go back in.....expensive little bugger too to replace!!

I've not looked into it on mine but is there any position under the front seat that the heater pipes could be T jointed and a supplementary radiator be mounted under the front bumper a bit like the abarth 850tc had(not the full 1000tcr cooling type though)

This way it would be in the natural air flow

FR85 said:

Other then internal heating what is the main issue with running without the stat?

Click to expand...

My understanding is the thermostat creates a small amount of back pressure even when fully open. This helps with the heat dissipation from the cylinders to the water (happy to be corrected, I'm not an engineer). The other more obvious change is that without the thermostat the warm up time will be increased. Not such a problem as I don't intend to use the van in winter.

A secondary radiator spurred off from the heating pipes is a possible option - there is plenty of space underneath the van. However, to avoid the rad quickly clogging up with road gunk etc. there would need to be quite a bit of ducting needed to keep a clean airflow.

Having said that, one of the forum members regularly drives his van across the Australian outback without problems so it shouldn't really be needed.

I have a horrible feeling that I'm in for a numptie moment and that I've missed something really basic.

Hi Gary. Can I ask if it's possible to take a photo of the side of the head where the spark plugs are showing the full height of the head.
Tim

Hi Gary. Can I ask if it's possible to take a photo of the side of the head where the spark plugs are showing the full height of the head.
Tim

Oooh double entry whoops.

Alternatively measure the actual thickness of the head. I'm just thinking if the head has been skimmed too many times the compression might be too high and hence making it overheat, ours was marginal on the cooling for a while and I put a 1.8mm gasket on it and it helped. Later on I used a standard 1.2mm gasket and machined some metal out of the combustion chamber.

In relation to the second rad I'd not be worried about road gunk if you are not going to be driving in winter. The gunk you find in the main rad will be far worse given a lot of it will be oil and vapour based and it forced in via the fan. I am convinced cleaning the main rad with compressed air and blowing it from the other side in the opposite direction to the fan sorted a lot of my problems, it was caked with crud to the point light wasn't visable through it. Also there was zero warm air being felt from underneath where as now it's jetting warm air out below.

It to me all seems to be rad and/or thermostat related. Cleaning the rad and removing the stat at least would,d trouble shoot and eliminate those.

None of my 850's have dirty rads. I generally put an acid through the water way to clear out any chalk(I live in the chilterns) also I clear the exterior of the fins with a degreaser when I take the rad out. I do have a newly reconditioned 900t radiator(high efficiency core) that I've never used, I shall have a look at it and compare it to a coupe rad.

Tim

Attached is what I mean, this is a spare rad I have, the one on the car was 10 times more gunked on the outside and in the veins then this.

Connie's rad looks factory fresh, I think the previous owner replaced it not long before we bought her 19 years ago at 70k miles. In the few years we had her on the road we clocked up another 10k and the over heating in traffic was a regular problem - hence looking at adding the electric fans as part of the rebuild.

Getting a full height photo of the block wasn't easy but here's a couple of photos to give an idea (one showing the heat tape on the 4-branch exhaust).





As far as I'm aware the head has never been removed. It's on my to do list as there is a very slight oil weep on the exhaust side - only noticeable because I cleaned the engine before refitting.

The second image also shows the blanking plate for the old fuel pump. I kept the original bolts just in case I had to refit the pump... best place not to lose them was in situ.

It looks like you have plenty of meat left on the head so it wouldnt be too much compression.

Gary50 said:

Connie's rad looks factory fresh, I think the previous owner replaced it not long before we bought her 19 years ago at 70k miles. In the few years we had her on the road we clocked up another 10k and the over heating in traffic was a regular problem - hence looking at adding the electric fans as part of the rebuild.

Getting a full height photo of the block wasn't easy but here's a couple of photos to give an idea (one showing the heat tape on the 4-branch exhaust).

As far as I'm aware the head has never been removed. It's on my to do list as there is a very slight oil weep on the exhaust side - only noticeable because I cleaned the engine before refitting.

The second image also shows the blanking plate for the old fuel pump. I kept the original bolts just in case I had to refit the pump... best place not to lose them was in situ.

Click to expand...

The oil weep could be from the rocker cover gasket, check that out before removing the head. Also look at the vapour pipe on the filler cup, mine weeped from a slight crack in the hose

In the past I've had oil seepage from between the block and the head where the pushrods are as the oil drains down there on the inside and its offset from the head bolts clamp pressure. Most of the new gaskets have a silicone line around the edge to help with this.

Still doesn't help with the cooling issue though.

One snapped bolt and several skinned knuckles later the thermostat is no more.

Made next to no difference with the hot running and now takes much longer to warm up - therefore needing to run on choke much longer.

On the plus side the thermostat was okay and the bolts and nuts are now all freed up, making removal in the future much easier. I will need to put the thermostat back at some point - although I'm tempted to fit an in-line thermostat housing (to avoid the risk of damaging the thermostat housing in the future - rare and expensive to replace).

To recap, the extra fan behind the louvres makes a huge difference and the combination of the two electric fans (the other fitted on the rad) and original mechanical fan seem to keep the dashboard temperature gauge at around 3/4. Open up the cabin heater and the gauge drops to around halfway and is steady around this - I took Connie out for around 45 minutes in mixed driving much of it at 50mph. Interestingly, the temperature gauge on the 123 Dizzy reads a constant 90C and the electric rad thermostat reads around 80C - regardless of what the dashboard gauge reads. Maybe the dashboard sender unit is faulty?

Overall though it appears to point to a partially blocked radiator core. One for further investigation/more powerful flush and/or a new core. Either way this will have to wait as we are moving house soon and loads of DIY to do.

Sorry, I feel now like I gave you a bum steer on the stat removal but when I combined the system flush with the rad flush and compressed air clean it transformed mine. Rad removal is very simple and well work doing, as I said shine a torch or light through it and see how clogged it is.

Best of luck with the move and DIY, hope it goes well for you!

No worries. The stat was 20+ years old so potentially it may have been only partially opening - especially as it had been dry for a few years when the engine was sat on the garage floor. Luckily I had a pair of thermostat gaskets as part of a engine gasket set. These aren't easy/cheap to obtain, so if I have to take them off again I'll probably need to cut my own.

I've used rad flush a number of times, both with the radiator in and out of the van. I know there is more heat from the 4-branch exhaust but I can't believe that the tolerance is so marginal that this would cause all these problems - and I'm not putting the old exhaust back on.

The rad fins are clear and air flow is good, so everything is pointing to a serious blockage in the rad core - it's the only thing left to replace. Once we have moved I'll take the rad out and fill it up with rad flush and leave it for a few days. The worst case scenario is that it might spring a few leaks but as it's not doing it's job it's worth the risk before I need to get it replaced/recored.