Overheating Roadster

[J_Phillips]

Re: Overheating Roadster

Martin, good to hear from you and thanks for your ideas. Yes, the electric fan is on the front of the radiator, between the rad and the mesh of the grill. It is directly clinging limpet-like to the radiator cores! The thermostat is set to max (or min, whatever the definition) and switches on the fan as soon as the ignition is on, irrespective of the engine temperature. At idle, I get up to 2mm from red (on the Marina gauge, i.e. well north of Normal) and on motorway @ cruising 70, it's about 1mm from red, about to explode, with the heater on full blast, it's not the most fun. Running 95 octane unleaded. Good luck with your build, I would hope you have less of this as an issue, with teh 1275 engine. Best wishes James

[HairyDave]

Re: Overheating Roadster

Re running on. An Anti Run on Device was fitted to some 1800s as seen in the Haynes manual. There was one on mine but not needed so far so it is not connected. The ARD is a solenoid-operated valve connected to the inlet manifold and operated by a 'Normal open' oil pressure switch. I have a three-terminal switch. 1 supply 1 N/closed oil pressure light 1 N/open ARD. When the engine is switched off the residual oil pressure closes the contact and opens the ARD valve to the inlet manifold flooding it with air and the engine stops. Wiring it is a bit of a pain so it is not connected.

[J_Phillips]

Re: Overheating Roadster

Hello Lil_red, I've not checked timing and mixture, specifically, and TBH I'm not sure what I'm looking for, but I see your guidance so thank you for that. It's running nicely (except when it gets majorly hot, so something of viscous circle perhaps). A million years ago, I did change the stock carb needles for something else, but I have no idea what, probably some sort of go faster flavour. Re jets, Waxstat does not ring any bells. I think I know that my twin SUs are worn somewhat, maybe I need to spend the ££ needed and just replace them, since I'm not really sure what I'm running. I also fitted a go fast cam from Piper or someone like that, some time in the 90s which as I recall made no material difference (as neither did the jets) so that also may not be helping but again I have no idea what flavour it is. My distributor is a standard vacuum advance type albeit with an electronic ignition converted, type/style I don't recall right now. I'm thinking it might be time for some professional help for the timing/mixture set up.... Best wishes James

[J_Phillips]

Re: Overheating Roadster

Dave, thanks re running on - I will put this ARD feature on a list of projects to get to
Meantime I'm switching off in 2nd with foot on the brake and stalling it!
Best wishes James

[J_Phillips]

Re: Overheating Roadster

Gareth, I'll look into that, I've just researched what you mean - now understood. Thanks and I'll add this now to the long list of actions I can/can consider taking to sort this out. Interested that no-one has suggested an oil cooler, would think that this might help too. BW James

[duncan]

Re: Overheating Roadster

Hi Guys
A Marlin with a clean radiator core should have an absolute ton of excess cooling capacity

I would suggest first buying two temperature probes and looking at the water inlet and exhaust on the radiator

If the radiator core is not clogged and you don't have something silly like the fan blowing backwards then the most likely fault would be in the water system

Thermostat, water pump, blocked passages - airlocks

The water in/out temp will tell you a lot

[milliemarlin]

Re: Overheating Roadster

As lil_red_roadster has mentioned in my limited experience lean mixture is the most likely cause of overheating in a kit car. A standard engine fitted with a free flowing exhaust, sports silencer and performance intake filter, exacerbated by E5, soon to be E10 fuel, is likely to run lean. In this country with typically low ambient temperature (excluding the last few days) is more than adequate to cool a relatively small radiator. This is particularly true if overheating occurs at speed.

One thing to check is your spark plugs Spark. Spark plugs that are clean or white is an indicator of lean running.
Paul

[HairyDave]

Re: Overheating Roadster

Re ARD, It can be wired in with just a switch turn ignition off. Turn ARD on when the engine stops remember to turn it off!.
Dave

[Gareth]

Re: Overheating Roadster

Gareth, I'll look into that, I've just researched what you mean - now understood. Thanks and I'll add this now to the long list of actions I can/can consider taking to sort this out. Interested that no-one has suggested an oil cooler, would think that this might help too. BW James

Hi James, if you look at my early posts from a couple of years ago, I put some pictures of the blower and also the metal fan which should help you. Gareth

[Ye Ol Ripper]

Re: Overheating Roadster

Hi James
I sent you a PM early yesterday providing you with advise to solve your overheating problems and have a Roadster running cool even in the recent 38 deg heat, whilst in traffic or on the open road.
Can you confirm if you have received it? There should be a notification showing when you log in at the top of the page.

[stevejgreen]

Re: Overheating Roadster

Hi James
I sent you a PM early yesterday providing you with advise to solve your overheating problems and have a Roadster running cool even in the recent 38 deg heat, whilst in traffic or on the open road.
Can you confirm if you have received it? There should be a notification showing when you log in at the top of the page.

Why not pluck up the courage and go into print yourself like I have done, rather than keep it to yourself.

If you have a tip that would add to my document, I would gladly add it.

What is clear is that without an IR thermometer it is impossible to validate a sensor, gauge and mechanical voltage regulator and ultimate temperature measurement by a 70’s era gauge is anywhere near accurate.

Many gauges of the 70’s era were simply approximations at best, there for guidance only.

[duncan]

Re: Overheating Roadster

I will add to my remarks about two temperature senders

If you know the water temperature going into and out of the radiator - top and bottom hose - you can instantly see what is going on

This will tell you if your problem is water circulation or engine or radiator

You can get a 12v temperature gauge and sender for about three pounds - the cheap ones will not last very long but they will tell you what is happening

[stevejgreen]

Re: Overheating Roadster

I will add to my remarks about two temperature senders

If you know the water temperature going into and out of the radiator - top and bottom hose - you can instantly see what is going on

This will tell you if your problem is water circulation or engine or radiator

You can get a 12v temperature gauge and sender for about three pounds - the cheap ones will not last very long but they will tell you what is happening

In essence that’s true. But it’s also true that the radiator as recommend by Marlin was significantly undersized for an 1800 B series engine.

After 40 years of intermittent service where ‘father time’ has many winter seasons to intervene with hidden internal corrosion.

Without wanting to get too political, summers are getting hotter, adding to the stress on any cooling system, everything must therefore be optimal to get the most from open top motoring, it would be a shame to crack a cylinder head, put under unnecessary stress.

[Ye Ol Ripper]

Re: Overheating Roadster

I note on the MGB /Marina water pump that there are extra bolt holes, so this got me wondering if there is another pulley for the water pump that holds the fan belt that is a slightly smaller diameter than the original.

If so, from another British car of that era, then the water pump would then turn faster for any given engine speed.

I haven't a clue whether it will help but certainly worth investigating.

Has anyone explored this avenue of thought?

[stevejgreen]

Re: Overheating Roadster

I note on the MGB /Marina water pump that there are extra bolt holes, so this got me wondering if there is another pulley for the water pump that holds the fan belt that is a slightly smaller diameter than the original.

If so, from another British car of that era, then the water pump would then turn faster for any given engine speed.

I haven't a clue whether it will help but certainly worth investigating.

Has anyone explored this avenue of thought?

A track through the parts lists, (guess where) might help, it’s an interesting avenue to investigate, but not for me.
Simply speeding up a pump does not necessarily increase the water flow, there is a complex pattern of cavitation that can rapidly destroy any perceived benefits, as well as the pump vanes.