Hi Guys,

Since 3 weeks I am the proud owner of a 2001 MGF. Driving it I noticed that the coolant temperature stays low to very low , behaves erratic all the time, and it takes a very long time before the coolant/oil temperature reaches a 'normal' level compared to all my other cars, if ever!

Ambient temperatures are low at the moment, in the region of 1 to 7 degrees C.

Two days ago I decided to 'duct-tape' all air intakes at the front of the car more or less shut and 'surprise-surprise' coolant temperature reaches the normal level (one notch below the middle) in about 5 minutes en oil reaches a 100 degrees in about 10 minutes. Both 'rock steady'...

One of the main reasons for head gasket failure is thermoshock because of the amount of cold water from the radiator and the position of the thermostat. IMHO this steady temperature AFTER duct-taping the inlet decreases the thermoshock risk, doesn't it?

Is there something wrong with my reasoning? Is there anybody on this forum with experience with taping off the mesh inlets? (I can't think of anything against this procedure because oil and coolant temperatures are normal now and steady....)

I am curious what other forum members think about this...

Hi Alex,

from your description I would say that either the thermostat is stuck open or a previous owner has removed it to “improve” cooling. Had the former on my TF when I bought it and the latter on a friend’s car this year.

With the TF having a PRT fitted, putting a new ’stat in was quite easy, on an “old school” vehicle this is a bit challenging. On my friend’s car (as I know there was no thermostat fitted) I swapped the hoses for the PRT setup (story here).

Duct taping will of course hinder the air flow through the radiator but might lead to problems in slow moving traffic. So you should rather find the roots of the issue and get it fixed properly.

Thank you Mykel, your reply sounds logical.

The thing is that I'm awaiting the delivery of a lot of components from Rimmerbros to change the head gasket (SAIC/Oil rail) timing belt and cooling system as a preventive remedy. (I wil be fitting a remote thermostat + bypass). It will be interesting to see if you are wright! (I'll let you know...)

Hello Alex!
I have the same problem since one year. The Thermostat stucks open all the time. But this prevents the thermal shock because the water-circuit is all the time open. But the warmup is incredible long and the heating is at 0 degrees outside very low. And as Mykel said ducting the inlet can be dangerous in city stop and go. Change the thermostat to 82 dgrees instead of the original 88.
I drive with this stuck thermostat since 2 years without Problem, oiltemp is at 90 to 100 degrees, no bad signs of beeing too cold.

Hi Sepp,

Thank you for replying! I am not so very worried about the temperature in stop&go traffic, to be frank. Yesterday I did some and the temperature stayed solid. The cooling fan did not even kick in. When really stuck in traffic there is no circulation whatsoever standing still and than the cooling fan should be able to circulate enough air, doesn't it?

I will nevertheless check the thermostat in days to come and plan to fit a remote 78 degrees one,. as recommended in the nearly scientific article on Dieters site... (written by Dave Monk)

I found a beautiful remote thermostat housing on eBay and received it last week. for the other end of the bypass I plan to use the revotec couplings.

have a nice day!

Alex

Without thermostat (in fact the same as a stuck one) the water temp goes along with the oil- and block temp, depending on the accelerator pedal...
So no thermal shock will come up. Like with my Jaguar MKII, 75 to 85 degrees water, but the heater-radiator is bigger.
To make the Long short, no problem at all (as you said the fan will do the thing, but this is not valid in all situations) and as long as you can stand the temp inside the car...

Yesterday I finished the head gasket replacement and all looks well! No leaks, no hiccups, and a normal operating temperature. I came to the conclusion that in its former life someone removed the thermostat without altering the cooling system, so that has been the reason for the erratic behavior of the engine temperature. This is what the new thermostat & bypass looks like:

Well done at the easier location in front of the radiator.
Thanks for sharing

You're welcome Dieter! Your site was my main source of inspiration & information...

@Alex. Well done, this thermostat will be my next Project. Btw, the fittings are selfmade or buyable products?

Hi Sepp, I found this thermostat housing on e-bay (USA). Search for "billet inline Thermostat Housing" and you will find one for 50,73 euro's with a 'bypass or sensorport'. They make them in badges, but there are still a couple left. I had to change the thread for the 'schlauchstutzen' from 1/2" NPT (can't get that anywhere in The Netherlands) to 1/2" BSP, but that was easy. In it I used a Gates thermostat of 82 degrees Celsius as in most Lotus Elises and it works like a charm. Watertemperature is at a normal level in about 4 kilometers normal driving and oil temperature in about 8 to 10 kilometer (80 degrees). Watertemp. is very stable at one notch below the halfway mark; oil never goes higher than 100 degrees with the actual ambient temperatures and fast driving.

All in all I am very satisfied with the way things turned out to be! I changed the head gasket, plugs, timing belt, oil rail, SS-cooling pipes, etc. I painted the subframes, cleaned out the wheel arches and applied a fresh coat of 'bodyschutz' to the underside of the car and changed the tires to Vredestein Sportac 5's so it should be serving me well for the years to come!!!

(The tires are a succes as well... less noise in the car and far better cornering than with the Continentals formerly used under the car! In the future I am going to try Bridgestone Potenza's -semi slicks- as I did on my Caterham, I think the car can handle them...)

It's a joy to drive!!

Have fun!

Alex

Had some further research for different sources just to enhance my website and provide some more info.
https://www.mgfcar.de/thermostat/

Remote Thermostat or pressure relieve thermostat are terms to look for.
likewise PEL500110 is mentioned already on the webside.

New for me is this one: GATES TH35882 (has the low 82° Spec).
(Not sure whether the hose diameters will fit with 35 and 33mm connection.

The T-piece is another case.