DTR - Project Recommission 1972 'Dolomite' Manual

[Mahesh]

When testing the senders, leave them in the same spot to get to room temperature for at least
30 mins to 1 hr.

[James467]

When testing the senders, leave them in the same spot to get to room temperature for at least
30 mins to 1 hr.

Yep, did that. Not intentionally mind!!

Driving it now the temp will rise to under 3/4 then will stay there no matter how hard I push it. I am not sure if the fan is cutting in and out, I'm pretty sure it isn't running all the time because it wasn't on when i pulled up to the traffic lights at the end of the slip road.

I'd like to wire in an indicator light to tell me when the fan is running, I'll get an LED and wire it into the power terminal to the fan that should flick on and off as the fan comes on and off.

[Mahesh]

Do a quick check to make sure the temp gauge goes over the 3/4 mark, just to be sure your not hitting the
gauges limit.

I used a led toggle swtich, lights up when the fan is on, and I can swtich on the fan if I want to with the ign
off, the cover acts as a failsafe to revert back to ign temp switching, mounted on the fog light swtich bracket.

[James467]

Yep, already got the revotec fan controller switch on there.

Gauge is fine!

[MIG Wielder]

I have some different temperature senders to try.

Hi James, As Mahesh says, these senders are very temperature sensitive. As an example my original Smiths sender reads 682 ohms at "room temp " ~ 68 deg F right now but hold the sensor element for a few seconds and it will rapidly drop to 610 ohms.
And the resistance is not linear with temperature.
Fro memory it is related by something callec "B" value which is different between sensors.
Now the one sender I do like is the 3rd original one:- like mine from your photos.
Can you check the d.c resistance from the copper bulb to the screw thread is <1 ohm please.
I see you have quite a clever dvm. Does it have a thermocouple accessory ?
If so can you check with the sensor in an oil bath at various temperatures please ?
( If not I can help with this )
It would be interesting to compare all 4 units.
Ta,
Tony.

[James467]

Sorry Tony, I have had a busy day dealing with an unhappy child! Will do this later for you.

This one doesn't have a thermocouple on it, I can get one that has though, they aren't expensive.

Looking at the engine today I was wondering about fitting a 5/8 UNF hosetail to the water transfer housing at the back of the head and feeding it into the heater inlet to remove that hot spot.

[sprint95m]

Looking at the engine today I was wondering about fitting a 5/8 UNF hosetail to the water transfer housing at the back of the head and feeding it into the heater inlet to remove that hot spot.

Doing that won't remove the hot spot James
but it will give (some) more heat from the heater (when it is set to hot).

It won't work because it will only take a very small amount of coolant away from said hot spot, given the small diameter of the outlet in the transfer housing.




Ian.

[James467]

Ok, thanks Ian. I thought that by letting the water flow out of the back of the heat it may displace some heat, but if that's not the case I wont mess with it.

[James467]

DTR ran superb on Saturday across to South London in the heat, temp stayed between 1/2 and 3/4 on the M25, had a few big hills to climb as well. Accelerated up Leatherhead and Reigate hill happily, then all they way up Shepherds hill and Farthing down. On the way back we had to sit in bad traffic on the M25 and although it got hot there was never a problem, once on the A3 it cooled down nicely.

Still only done 650 miles on the new engine but it is as smooth as anything cruising at 75.

I'm tempted to drive into London in it tomorrow.

[James467]

We had the same power loss issue again but this time on the M3, luckily I was able to get it into one of the lay by's on the smart motorway bit between junction 4 and 3. Yes I was pushing it, deliberately, flowing with the traffic at 140kph the engine temps were fine.

It's funny, the fuel light was on and the gauge was reading under a 1/4 tank, when I left Hampton it was 1/2 tank.

The coil was VERY hot but the car would idle fine, I popped the bonnet and left it to cool a bit. Spoke to the highways agency, who I may add were absolutely superb, they offered to close lane one so I could get back onto the motorway safely but to be honest the traffic was so light it was fine.

Cruised back home with the bonnet popped and yes the temps dropped as you would expect but the car was fine.

I am not convinced that this is a fuelling issue (vapour lock), I think its one of two things.

The Lumenition optical switch is failing in high temperatures.

or

The coil is failing, it was extremely hot.

However, something is bothering me and that is the fuel gauge reading, after setting off again it went back up to just under 1/2 so I am also wondering if there is a fuel tank venting issue as well?

I have a Bosch coil so as I have a spare dizzy so I am going to set it up on points and swap the Optronic dizzy for the points dizzy and run down to Hook and up Beacon Hill and see if does the same thing, it's safer for it to fail off a motorway! If it is fine then we can deduce that the Lumemition system is at fault, if it does it again then we can rule that one out, if it happens again I'll take the tank cap off and see if there is a venting issue if not it's probably the coil which needs moving to the bulkhead anyway.

[Tony Burd]

I had a fuel gauge problem the other day turned out to be the earth connection on the sender.

[Mahesh]

James I think you have the same problem as I have.

The electric fan blows heat from the rad right up to the coil passing the carbs.

All is well until fully warm, then the fan cuts in and the coil heats up.

[Galileo]

Musing about this, wondering if with the stock fan at idle the fan is only doing roughly 1000rpm (I've not measured the pulley size difference) so wafting air through the rad and around the engine when stationary but the electric fan is going full speed no matter and so shifting a lot more heat unto the engine bay? With the standard set up and moving along the air would be dragged out of the engine bay in tandem with the increase in fan speed so heat would not build up. I'm playing the devil's advocate here, as since fitting a Sprint rad the only issue I have is stiff steering in traffic when it's hot.

For example, Friday's journey home from work in 28°C was a 'spirited drive' for 30 minutes up until the last 5 miles which was full on stop start crawling traffic (A14 *shakes fist*) all the way to my front door. There was no spluttering, no loss of power, just the usual stiff steering and the shaking itself to bits when pulling away (engine mounts maybe? Dunno, fine in anything <25°C).

One thing that I think is a must is having the original air filter box with the cold air feed tubes in place. When I first got the car the PO had installed K&N* pancakes, sounded good, drove like s##t in traffic when hot, spluttering, stalling and not revving so I bought an original air box but didn't put on the hoses until recentish, first step made a huge difference when hot, adding the hoses eliminated all issues. The only non standard thing other than the electric fan I have is a Viper 12v dry coil.


*Nothing wrong with a K&N as such, on my Golf I had a K&N but quickly discovered that it did not like the under bonnet heat and so put a piece of ali sheet across the wheel arch to the front slam panel to separate the filter area from the engine. Problem completely fixed, drove great, even in Spanish 40°C+ heat and caning it around the Nurburgring...

[James467]

You could be right there, but the electric fan was running so that should have blown air out of the car.

Interestingly the optical switch on the Lumenition has a maximum operating temperature of 120 degrees. I'm going to tape my cooking temperature probe under the bonnet and see how hot it actually gets under there when I'm giving it some beans. It could be getting so hot that the optical switch is outside of it's operating range.

[Galileo]

I was thinking more about Mahesh's point, wondering if an electric fan actually could generate a higher under bonnet temperature or at least more directed at the carbs/coil areas, by shifting more heat out of the radiator when stationary. I think that's what I meant, it was still early for me when I wrote that!