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MG TD TF 1500 - Overheating - ...And so it begins

Some of you may recall that my TD (25009, XPA/TD2/25404) has been suffering from severe overheating when I drive up our lovely Blue Ridge Mountain roads. Recently the temp needle went up into the oil pressure range and the overflow tube was insufficient to relieve the pressure. When I attempted to remove the cap, the pressure blew the cap over 12 feet straight up.

I've had the radiator refurbished and I've used the expensive radiator/block flush all with no joy. So, now it's time to ensure that (1) the pump is actually moving coolant through the block and head and (2) that the water passages in the block/head are actually open to allow the passage of coolant.

Toward that end, this afternoon the lump came out. We disconnected all the peripherals and removed the radiator. We were able the pull the engine/tranny without having to remove the newly installed floorboards although we did cut reliefs in the floorboards to gain access to the bolts holding the rear tranny mount.

Now, disassemble the thing and take if to the machine shop for a thorough internal cleansing. Also, the "freeze" plugs have started leaking so they will be replaced with Tom's good ones.

In the "while we're at it" category, I'm also installing a new Bell exhaust system and Len's roller cam stuff.

Updates will follow is this project progresses. Wish me luck.

Jud

ps: Sorry, still haven't figured out how to get iPhone pics to be rightside up.





J K Chapin

I hope you weren’t scalded by hot water. Thats why you never take a radiator cap off a hot engine. Even on an open system. I learned this lesson the hard and very painful way when I was in high school.

There is a transition hole between the inner and outer block core water passages. The hole is inside the front and rear side core plugs on the manifold side. If these are plugged up with sediment the engine will overheat.

If you have not invested in a modern thermostat and housing I highly recommend Tom Lange’s SS item. Stay away from the aluminum housing as there have been write ups on the forums about them quickly disintegrating.

It Is also possible you may have a cracked head or a cracked cylinder wall causing hot combustion gases to enter the cooling system.

Let us know what you find out

W A Chasser

Also invest in a water pump with a 6 blade impeller.
W A Chasser

Gee...looks like the engine could have fallen right out of the car :-) Try turning your phone 180 degrees next time you snap a picture and see if that works.
L E D LaVerne

Go to photos. Click on the pic. Click on edit then click on the lower right icon.
(Looks like a square with arrows circling) Top left corner will be two icons. One flips the pic for a mirror image. The other rotates.

W A Chasser

Keep in mind that the cooling system only accounts for around 11% of the heat removal from an engine. The oil/lubrication system also accounts for 11%.

Make sure both systems are working as they should.

The other 78% goes out the exhaust pipe as hot gas, and by radiation and conduction.
A L SLATTERY

Jud,

Here’s a link to an article concerning the “hidden” water passages mentioned above. If they’re blocked they’re definitely hidden.

Gene
Gene Gillam

Jud - I don't mean to beat a dead horse, but along the same lines that most carburator problems are electrical, the best coolant repair you can ever do is having the distributor rebuilt by either Jeff Schlemmer at Advanced Distributor, or Rob Medynski at British Vacuum Unit.

The distributor is the variable in the engine's timing, and if it is worn or otherwise not adjusted properly, it can certainly cause overheating.

Plus, you will be surprised how much better your car will run!

Tom Lange
MGT Repair
t lange

Whoops, here’s the link: http://www.mg-tabc.org/library/the_hidden_water_passage.htm

And I agree with Tom...check your distributor/timing.

Gene
Gene Gillam

JD,
The cooling system on a TD is supposed to be NON PRESSURIZED !! Find out why it had soooo much pressure to blow off the cap !!
Also, Tom s suggestion is very good! check out the dizzy..

Steve
SPW Wincze

When I replaced my re curved T type distributor, as recommended by one of my camshaft customers who dyno tested the CSI distributor on all 16 programmable advance curves,it was better out of the box, but when I set it to my customers recommended curve it transformed the performance!
http://www.csi-ignition.nl/en/dealers/usa.html
T type Lucas 23 D (type housings) in stock as well as 25 D with a vacuum advance ( it helps lower coolant temperature) for those with MGA TR3 1 1/2" carbs with a vacuum port.
Len Fanelli


Len Fanelli

When my TD overheated I saw steam coming from the radiator overflow pipe
As already stated I am surprised there was a pressure build up on an open vented system !
Mel Pascoe

WA, I was slightly scalded and the pretty TR6 parked next to me was doused with rusty water but no lasting damage to me or it.

I've been in touch with Butch Taras about a 6-vane pump but he is having issues producing new impellers. I like Butch and would prefer to buy from him but I may have to shop elsewhere. Are there other vendors with good quality 6-vane pumps?

Tom, my dizzy was rebuilt by Jeff about 4 years ago so I think it's OK. I'll make sure the timing is set to 0 TDC static and goes to 32 degrees BTDC at 3K rpm.

Gene, great article. I knew about the "hidden passage but had not seen such a clear set of pictures of it. Thanks.

Mel, I'd been going very hard up a very steep mountainside on a very hot day. I watched the gauge crawl past 220F and when it read 230F I stopped. I saw steam rushing out of the overflow tube and I thought (incorrectly) that I could safely remove the cap and add fresh water. WRONG!!

What I don't know is what I should have done - (1) let it idle hot; (2) shut it down and let it cool; (3) something else.

Jud
J K Chapin

I think that letting it idle would allow the engine to cool better
If it did not ease off after a few minutes I would then shut down and only open the radiator some ten minutes after steam ceases.
Top up water level very small amount over many minutes as cold water could shock casting and might result in a crack.

Of coarse this is easily stated here at home on the chair
Mel Pascoe

If you have the coolant passages cleaned out, which just flushing won't do it, long wire brushes through the core holes will get a lot out. if the head is off, it should make it easier. You would be amazed just how much rust can accumulate in the passages.
PJ Jennings

PJ, that's the plan. Thanks. Jud
J K Chapin

Cooling system was pressurized? Have you checked the radiator overflow tube? If I is hit from below, clogged or blocked with something like a mud wasp nest, the system will pressurize, and the car will overheat. I drove with an overheating problem for years, flushed the system, rebuilt the distributor, messed with the timing, etc. finally figured out the overflow tube was blocked. ,
D. Sander

J K Chapin, with an overheating car that still has coolant in the radiator, it is best to let the engine idle and pour cold water continuously over the outside of the radiator to help cool it. Once the temperature drops into safe territory you can shut it down and let it cool right down before attempting to open the radiator cap and refill it. If you think the coolant is all gone, just shut it down and wait a couple of hours for it to cool down. Rapid temperature change in the head can warp it.
J P Hunter

Thanks D and JP. Hopefully I won't have to face this again.

So, the engine is disassembled and a couple of things have been found.

Image 1: I think I'll replace this piston and, while I'm at it, all four. This is piston #1. The others look OK but they will all be replaced. Has anyone had experience with the Moss Aerolite pistons? I'm already at 60 over so may have to bore to 80 over. Recommendations? Thanks.

Part of the lack of cooling problem may have been the rear plug in the block (image 2, the block is upside down on the bench). This plug looks like something from the plumbing supply aisle at Home Depot. It is so thick that it buts against the inner face of the block. The effect is that it severely, or completely, blocks the coolant flow to the rest of the block and up into the head. New plugs were already the order of the day and this one will go into the bin.

So, where we are: New exhaust (just because the old one is loud and I want a new one); New roller cam (the existing cam looks real good but I want the new roller can anyway); All new welch plugs; four new pistons and appropriate rings; honed or, if necessary, bored cylinders out to maybe 80 over; and, of course, all new gaskets everywhere.

I'll also inspect the recently replaced throw-out bearing because John Twist mentioned, and I've read, that some new throw-out bearings are defective and disintegrate after a very few miles.

That's all for now.

Jud





J K Chapin

The Moss Motors 6 vane worked wonders for me.
Peter Dahlquist

Holy crap Jud! That piston looks like it disintegrated and that back plug definitely was the wrong type of plug...but it's not your problem with the cooling...see this link: http://www.mg-tabc.org/library/the_xpag_cooling_system.pdf

Gene
Gene Gillam

Gene, that’s a great link but Pipe cleaners are probably more efficient than electrical wire for cleaning out all those passages🤡!
I also had a long session with a high pressure washer when I cleaned out the block on TF 2071 and was amazed at how much crud came out. Running temp is very stable and the MGB fan is probably overkill but I do live close to the tropics.

Chris
C I Twidle

I think the plug was indeed blocking most of the water flowing up the back to the head. Of course the head is where the heat is produced. I'm surprised it ran well at all and didn't make some really bad noises. I wonder if your hard drive and major overheat fried it? George
George Butz III

George, see the link above...water doesn’t flow up to the head from this point.

Gene
Gene Gillam

Just looked at carefully your pictures again to refresh my memory and of course you are right. But that blob of rubber plug corked up any flow in that local area. Likely the block is full of crud or something. George
George Butz III

Gene's photos are also at http://www.ttalk.info/XPAG_Cooling_System.htm. Bud
Bud Krueger

So yesterday evening we popped the plugs out of the block and attacked the block with my pressure washer. As foretold, copious quantities of slush and crud came flowing out. I believe that the engine flush that I had used helped by softening the crud but that, without popping the plugs, the slush and crud had nowhere to go. The block is now in the hands of my machinist who will finish the clean-out.

It appears that the cylinders have already been bored to .060" over. My machinist will check them for circularity and bore them out another .020". There is a very small amount of damage from that broken piston and that should be resolved by the additional boring.

The inner surfaces of the cylinders are mirror smooth. I expected them to show cross hatching from the previous boring. I guess the wear since the last boring has removed the expected cross hatching.

Today we disassembled the head. It was refurbed about 5 years ago and it still looks very good. It measures 2.995" thick. Although my block is 25404, the head is a banana hole from a pre-22735 engine. I've found a previous thread where Mort notes that the head was originally 3.022" thick so mine has been shaved a smidge over 0.022". In the same thread LED states that removing up to 0.100" is not uncommon so I think I'm still OK.

I have no idea whether blocks are shaved nor, if so, whether mine has been shortened. Again, my machinist will check for flatness and do whatever magic may be required.

The reason that I care about this is that I'm getting new push rods from Len and this information will, I think, be necessary in choosing the shims to go under the valve train towers.

The next step is getting confirmation from my machinist that I need to order +.080 pistons and rings. Waiting is less fun than doing but, at least, I have the A and the B to drive around in.

Jud
J K Chapin

Yesterday and today were Red Letter Days!! Yesterday several club members and I successfully reinstalled the rebuild motor and started her up. It started easily and ran smoothly but with no radiator attached and no coolant we ran it for only about 30-45 seconds.
If I knew how to post a video I'd let you see and hear it.

Today we reinstalled the radiator, tunnels and seats. Added coolant and fired it up again. Sitting in a 60 degree F shop with no motion, the temp rose to 75C and just sat there. We ran it for about 10-15 minutes and the temp was absolutely stable. In addition, after shutdown there was no noticeable residual heat - the gauge never climbed above about 77C.

After a celebratory brewski we took it out for a 5 mile shakedown cruise. The ambient temp was about 40F and the coolant temp never rose above about 50C. Mostly because, I think, the engine never really reached proper operating temp (BTW, there was also no bonnet), there was some rough running that smoothed out with the application of about 1/4 choke (enrichening). Again, most pleasantly, when we shut it down there was virtually no residual heat rise.

The new Bell exhaust system sounds great. Len's roller cam and lifters appear to be pushing the pushrods up and down. The oil, water and smoke all stayed where they are supposed to be.

All in all, a Red Letter Day!

Jud
J K Chapin

Glad she’s up and running again for ya!
W A Chasser

Thanks Bud that link was very helpful to me as I THOUGHT I'd completed my water jacket cleanout but will have to check those two holes. PLUS have managed to clean between barrels 1 and 2 and between3 and 4 with a small hacksaw blade vise between 2 and 3 needed. Is there a passageway and if so other than air and pressurer washer any advice on clearing. I have incidently had the block in an electrolysis tank derusting.
JK Mazgaj

Jud,

Earlier in the post you refered to setting your static timing at TDC. If your distributor was reconditioned by Jeff, you should be able to set your Static @ 8 to 10 degrees BTDC. That will further help with over heat issues, and as other's say.... will result in a little better running.

... CR
CR Tyrell

Thanks CR. I do think I need to advance the timing. For reasons I can't recall I thought the appropriate starting point was 4 degrees BTDC at idle but I just read john Twist's tune-up guide which suggests 13 degrees. I'll try that.

Also, when we went to hook up the fuel line between the pump and the rear carb it was about 1/2 inch too short. This leads me to believe that the motor is further to the front that when we started although I can't see how that could happen. Anyway, I replaced the large diameter Moss woven stainless hose with a smaller diameter woven stainless slightly longer hose that I just happened to have on hand (can't remember why). Is it possible that the smaller hose is restricting the fuel flow enough to cause the engine to sputter from fuel starvation?

Tomorrow is supposed to be sunny and high 60s F so I'll get it out for a longer drive and see if I can get the motor up to proper operating temp. I remembered last night that when it was overheating we removed the thermostat and we haven't put it back in. That will be rectified this weekend.

Thanks.

Jud
J K Chapin

Bud. The one hole existed. Not the second. But does now. Still no answer to how to clear between pots 2 and 3! If what was between 1 and 2 and between 3 and 4 even after electrolysis and "boiling" and pressure washing was anything to go by.
JK Mazgaj

Jud - I'm puzzled that your pump-to-carb fuel line is too short, and doubt the engine could be moved that much. As I remember, the pump line is 16", and the carb-to-carb line is 14", with plenty of slack in the installation. A TD/C line is 18", so you could use one of them in an emergency, but I still don't understand why you might have to.

Tom Lange
MGT Repair
t lange

I'll measure the old line and make sure it's for pump to carb and not for carb to carb. Maybe sometime in the confusion of the project it got switched. Thanks for the hint.

Jud
J K Chapin

I just received my stock dizzy back for Jeff@Advanced and he suggested to set the timing 14-16 BTDC. I haven't installed so I'm not sure how happy the engine will be.
Bill TD24570
Bill Brown

I measured the old pump to carb hose and it's 14", supposed to be 16". Don't know how it reached before but it doesn't now. The smaller OD 16" hose seems to be working just fine.

Friday we reset the static timing to just a tick before TDC but the weather was horrible so no test drive. The car ran great in the garage for about 45 minutes but with no load so not a fair test. At least we confirmed that the overheating seemed to be cured.

Saturday was a 200 mile mountain drive. I didn't want to take the untested TD so I drove the MGA MkII. It, of course ran great and it really spoils me.

Back to the story - Today the ambient temp is about 70F so we took the TD up the mountainside to a wonderful BBQ place in Saluda. Because I have not reinstalled the thermostat, we blocked about 2/3 of the radiator. That was too much blockage so pulling the steep hills and curves caused the temp to go up to about 105C. Once we got on the plateau the temp came back down to a respectable 90C. When we shut down at the BBQ place the temp stayed about 90C with very little overshoot from residual heat in the block/head.

After lunch we headed back, mostly down hill curvy. We removed the radiator curtain and the temp stayed between 75C and 85C. The motor seems to run best at 80+C.

Oh, by the way, I should mention that with the new cam (Len's rollers), the new pistons (80 over) and the new Bell exhaust it runs great, pulls hills great and sounds GREAT!! I'm just ecstatic! I feel like I've got a new car. Real wide torque band. Revs from 3K to 4.5 K very fast even up a 4 t0 5 degree slope. Just wonderful.

Jud
J K Chapin

Sounds like you’ve got it licked, Jud.
Congratulations!
Gene Gillam

"even up a 4 t0 5 degree slope."

Oops! I meant to type 4% to 5% grades.

Anyway, it goes up steep hills much better than before.

Jud

J K Chapin

I blew a frost plug on the track once in my TF. Took only a couple of minutes for me to have pistons that looked like Jud's photo.
D A Provan

The initial Ignition timing is a starting point but what you really need to look at is your total advance at about 3000 rpm to prevent detonation. This should be in the 28-32° range depending on compression, the cam and the octane rating of the fuel you are using.
W A Chasser

I won't further hijack the cam bearing thread. I dropped the tire pressure to 28 lbs. and put 110 miles on the TD today. It drove wonderfully except for the following little incident:
FBCC/BCCWNC Roadside Heroes

It was a beautiful March day and David Benson had invited me and Peter and Jeff to go for a drive in the mountains. It turns out that BCCWNC was having their drive to Jump Off Rock that day so we decided to join them. The “join up’ spot was on Hwy. 64 at Laurel Park just west of Hendersonville.

Well, driving up through Hendersonville to get to Hwy. 64 had no appeal so I scoped out a route that took us from Hwy. 176 just north of Flat Rock across some very entertaining roads that ultimately came out at Hwy. 64 a few miles west of the join up spot. We were all chatting on the walkie-talkies and most of the chatter was something like “Well, Jud’s got us lost again.” Oh ye of little faith. Some 55 miles later we came out just where I expected to and arrived at the gathering with 20+ minutes to spare.

I was in the TD with my just rebuilt motor running like a well oiled sewing machine. Pulling hills like a draft horse and revving to 4.5K with ease. And, absolutely no overheating. Just wonderful. The crowd, about 20 LBCs, took off for the fairly short but twisty sometimes almost vertical drive to Jump Off Rock. From there we drove down to a nice coffee shop for a snack before heading out to Mitch Andrus’s place to see his Jag XK120 project.

Well, we didn’t make it and here’s where the Roadside Heroes story starts. We’re tootling west on Hwy. 64 toward Mitch’s place when – Bang!!- the TD stopped running. There were no shoulders to pull off onto but fortunately I had just enough rolling momentum to coast up to a paved residential driveway. [Miracle One: The owners weren’t home and they didn’t get home until after this tale is over] I sent SOSs over the walkie-talkies and the group, four FBCCers and three or four BCCWNCers, u-turned and came back to offer sympathy and help.

We quickly determined that fuel was doing what it’s supposed to and so we shut up that side and moved over to the electrical side. Plenty of battery to spin the motor but no spark. Removal of the distributor cap revealed that although the motor was turning nicely, the distributor was not turning at all. Clearly something between the cam shaft and the rotor was amiss.

OK, I’m ready to call Haggerty for a rollback but Peter and Mitch and the others would have none of that without seeing if a roadside fix was possible. Peter (Roadside Hero One) dives in and extracts the non-functioning distributor (all I have is a small crescent wrench but in the hands of an expert that’s all that is needed). There’s supposed to be a helical gear on the bottom of the distributor shaft and the shaft is supposed to spin easily in the housing. Well, in my case there’s (1) no helical gear and (2) the shaft will not turn at all. The consensus is that it’s broke. Once again, I’m pulling out my Haggerty card to call for a rollback. Once again, Peter and Mitch say “We can fix this.”

[Miracle Two] Mitch, who is a master restorer, says he’ll just tootle up to his place, pull the distributor out of his race TC (it has a TD motor) and we’ll just stick it in and Jud will be on his way. Fifteen minutes later Mitch returns with his distributor in hand and thirty minutes after that Peter has it in my car and it’s time to see what happens. My job throughout all this is to turn the starter crank to set the motor at TDC and to occasionally pull the starter knob to see if it will run. The trick here is to get the newly installed distributor lined up with the firing order of the motor, i.e., to fire plug one when piston one is approaching TDC. It’s either going to be plug one/piston one or plug one/piston four so it should be a 50-50 shot. Of course the first try was plug one/piston four but Peter persevered. A little fiddling and the application of some mechanical expertise later and [Miracle Three] “Varooom!” It starts and runs like a well oiled sewing machine. Unbelievable.

I have to thank, in addition to Peter and Mitch, Fred from BCCWNC for the use of his tool kit, another great guy from BCCWNC for the use of his ¼” socket drive extension, and the other FBCC and BCCWNC guys for their moral support. I also have to thank Julia and the lady with the BCCWNC guy for their patience.

In any normal universe I’d still be on the side of the road shivering and waiting for the rollback. In the universe of British Car Clubs I drove the TD home in glorious sunshine and without a hiccup or a sputter. That’s Miracle Four.

Thanks Robert and BCCWNC for a wonderful drive to Jump Off Rock and thanks everybody for making these outings the wonderful adventures that they are.

Safety Fast!!
Judson Chapin
1953 MG TD
J K Chapin

This thread was discussed between 21/08/2020 and 08/03/2021

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