Moss Motors, Ltd

Ok,  Here is the situation:  New radiator, new water pump, shroud, electronic ignition, rebuilt carbs, new valve job on head, new thermostat (180 and 160). All of this was done because it was needed. 

 starts right up runs fine, great idle but when I get out and drive down the freeway at 65/70 the engine heats up to over 190/200.  When I drive at 40 the engine runs at 180/190.  What am I missing here?

 
Suggestions?

 
Michael

 

Michael,

It's not all that unusual for you to get those readings. How old is your temperature gauge? They are notoriously inaccurate. Have someone check the actual temperature with a non-contact detector aimed at the water outlet of the head. Try installing a radiator shroud, and seal its edges well to the radiator. 

Also, what engine do you have? I have found over the years that for some reason the 1500s run generally hotter than the 1600s, but that if you've installed an 1800 from a B you'll have to take steps to improve the cooling.

How long has it been since the engine was overhauled? As things in the bottom end wear, you'll make less power and more heat. That's just the way of the physics involved here. MGA engine water jackets also tend to build up a bunch of rust and gunk which is extremely difficult to remove. This stuff inhibits cooling.

One last thing. Have you tried the bypass blanking sleeve offered by our host. It really can make a difference in the absence of the correct type of thermostst which is harder to find these days, and which used to block off the bypass as it opened. Also, try some Redline Water Wetter with a weak antifreeze solution. This nearly always brings down the temperature.

Just asuggestion, check your ignition timing. If the timing is to retarded the motor can run hot. Im proper cam timing can cause over heating as well. Have you done a compression chek since the head job? Compression to water leaks will certainly cause an engine to run hot, but you would expect it to run hot all the time. Hope this helps.

Rick

When I say this is a mystery I'm not kidding.  First I'm into this as daily driver  but it does need to be fixed correctly. 

Other details: Engine is 1500 with early B-18 Head.  Previous Owner did a lot of screwy little things that I have been fixing as they break.  When I bought her she had been sitting for quite a while.  All the previous stuff was things I had to do to make the her roadable.  (The brakes were a different story).  I agree that the temp gauge reads about 20 degrees hot.  This is based on delta's I saw when I moved from a 180 themo to the 160.  I can't speak to the bottom end of the engine but that could be the problem as this thing has a horrible sludge problem early on.  I'm running 100% antifreeze in the radiator.  It this ok?  I'll check the compression but don't believe there are any problems there (no bubbles in the raditor, etc).  I looked at the blanking sleeve but don't know if this would help given everything else.

I think I understand why having ignition timing retarded would cause it to run hot but I still don't get why timing chain would cause this a well.  Can you elaborate on this? 

Thanks,

Michael

Michael,

100% anti freeze will keep you from freezing up in the Antarctic, and it'll keep you from boiling over on Venus, but it won't cool your engine worth a darn in the real world. Antifreeze is not really a very effective coolant. Any more than 50% solution works specifically against you, and in the summer it's wise to run considerably less in an MGA. Try a 25% solution with a bottle of Water Wetter. You'll see a marked difference, I'm quite sure. Just remember to "anti up" in the fall so you're protected

I'm with you on the timing thing. Retarded ignition timing will cause hotter running due to greater water jacket exposure to the flame front, but significantly (and that ain't much) wrong valve timing wont do much in that area, mostly because you can't get the engine to run well enough to really produce any heat.

By the way, switching thermostats really doesn't do much to change the upper end of running temperature. Once a thermostat is open the engine pretty much runs at the temperature it's going to run. Thermostats actually work to assure rapid warm-up and to keep an engine from cooling too much in cold weather. If a thermostat isn't working properly, or is blocking flow by being the wrong type, that's a different story, but a properly operating 180 degree thermostat won't make your engine run any hotter than a 160 in the summer. It just takes a little bit longer to open, and therefore warms the engine to operating temperature a little sooner. The engine will achieve more than 180 degrees either way.

All,

 I wanted to close the loop on this as I think I just about have this figured out.  First thanks for all the thoughts and replies.  Between work and everything else I just haven't had a chance to post what I finally figured out.

 First and formost it was the timing.  I had put a timing light on the crank previously but for the life of me I hadn't been able to locate the notch.  I even turned the engine around by hand and tried feeling for the notch and still couldn't find it.  Finally I figured out that it was on the front of the pully and not the back side (Can you put this on backwards?)  There is not much of a notch left either to make matters worse.  I finally located the notch by pulling number one plug and l did a static timing with the piston up to TDC and making sure the points where pointing at #1 spark wire on the ingnition cap.  I then closely inspected the pulley.  With the notch located and painted the strobe showed the timing to be way way off.

I was amaze it ran.  It was idling nice and smooth, plenty of power etc. previously.  However, once I move it back to about 5 degrees before TDC and readjusted the carbs my gas mileage jump up about 8 MPG as well.  The shop manual only has the directions for a static timing.  What should it be with the strobe, the same as static?  (I do know to disconnect the  vaccum advance and keep it really slow so the weights don't kick in.)  What should the timing be when done dynamically?  I think I'm a lot closer now but not optimal. 

She still runs a little hot but not like it was doing before where it would just continue to climb.  At speed it tops out about 190 on the gauge and I think the gauge is off by around 15 to 20 degrees.  This is based on the fact that when it originally reaches operating temp and sort of stabilizes when I just driving around town below speeds of 40 MPH the gauge reads 180 degrees w/ the 160 degree thermostat. 

 I still have to drain some of the AntiFreeze out and put some H20 in and I think that should finish this thread out.

I read the thread on the "Water Pump" and the "Air Flow" Experiements.  If need be i can change the pully on the water pump to a spridet pully and pickup the additional flow through the increase speed on the pump.  I'm not read to go there yet but that is an option as well.

 Thanks for keeping me on track.

 Michael

I agree with motorbill on thermostat. It controls the lower end of temperature, not the upper end. Water wetter and ignition timing were real solutions for me. I was constantly creeping above the 212 degree mark at speed. You need to set the full advance timing to get it right. This will give you the best results at speed. Be sure the vacuum advance hose has a good airtight seal. Set 32 degrees full advance at 3500 RPM and it will be spot on. Of course, this approach depends on the distributor's counterweight springs that you have installed, but 32 degrees is good for stock springs. A dwell/tach and an adjustable timing light make this process much easier. If timing is advanced enough to help with overheating you will know it by how quickly the engine fires upon cranking. The shroud helped immensely in traffic...stop and go driving, but not much help at speed. The ram air effect takes over there. IMHO, 190-200 degrees is perfect! I started my early 5-main 1800 MGA for the first time in July '05 and it sees these temps as optimal for performance driving. I say grab a gear and go!

Darren.

MotorBill - I have had the same experience that my 1600 Engine runs cooler than the 1500.  What is the difference between the engines that would have one run hotter than the other?

-Devin

Devin,

My evidence for this is, I must admit, only anecdotal. However, I've observed it over a long period of years with a fair number of cars. I suspect there must have been some change in the block casting when the higher displacement engine was put into production. If I find out what this was (I seem to recall something about the "siamesing " of the center two cylinders for core strength) I'll post about it.

Thanks for the response.  I am more happy with my 1600 engine vs. my 1500 for the temp. reason alone.  I found myself looking at the temp. gauge constantly before.

Although, the prior owner had put the Fan on backwards on my 1500 engine.  I noticed this when I swapped in the 1600 engine.  How much of a difference would that make?

 Devin

Ladies and Gentleman-

Straight Anti- freeze causes cavitation in the waterpump because the viscosity is too high. This causes the coolant to not circulate properly. Also, it is not as good a conductor of heat as straight water is. This leads to overheating, especially at higher R.P.M.s. 

LCJUTILA 

Cavitation? I think the dentist said my kids have that chronic condition. At least the bills indicate so!

unruly,

Geez, you really drilled us with that one...