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MG TD TF 1500 - Coolant in cylinder

Picked up my YT from Upholsterer yesterday after he finished all the work I requested. It has been in his workshop for 5 weeks.

When we started the engine (it fired straight away without choke), but every 10-15 seconds there was a clunk / knocking sound, like metal hitting metal / tin. Killed engine straight away. Started engine a couple more times, to try and determine location of knocking but in the end the engine wouldn't start (ie siezed).

I had car transported to my shed and today I started investigating possible problem. On the suggestion of a club member, I pulled the spark plugs and found that #3 cylinder had coolant in it. I have removed carbs and exhaust manifold and top radiator hose, after draining engine in readiness to remove head tomorrow, and then check if head is cracked. I have a number of spare copper XPAG head gasket.

As engine will not turn over with the crank handle, can someone give me an idea where else to look as to why engine will not turn over. (rusted and broken ring(s)?)

My Jackall Ram and pump refurbishment will need to wait.

Thanks Stuart
Stuart Duncan

Stuart
Is this with the plugs still out
William Revit

Yes, with plugs out engine will not turn over.

Tomorrow, I need to check head to ensure the welding up of a PO attempt at smoothing inlets and outlets to manifolds is still OK. See photo of earlier problem.

I am thinking it may be a full engine dismantle again, after only a year since it was built.

Stuart Duncan

Hmm
sounds a bit nasty
Head off first and see what can be seen from there
William Revit

As water will not compress, Unfortunately, it sounds like you may have bent something.

Let us know what you find.
Bruce Cunha

As stated, water will not compress! Possibilities, bent rod, broken piston ????
PJ Jennings

Are you sure it’s out of gear? Easy things first.

Gene Gillam

Many decades ago I worked on a TD engine that had apparently hydrolocked. It ran OK but there was a strange ticking in the block. Upon removal of the sump we found that one rod had bent just enough to touch the bottom edge of the cylinder. We found that after finding a shiny edge to the rod. Replaced rod with a used one and changed head gasket and all was well.
John Quilter (TD8986)

I am a happy YT owner. Head is off. Only a few droplets of coolant (when looking in through the plug I must have been looking directly at one droplet), but I did find a mangled washer on top of #3 piston with a bit of scoring on top of the piston. Photo 1 shows piston #3 & #2 and the squashed washer that I have moved off piston. Photo 2 is close up of piston top

A while ago, I had problems with the inlet manifold gasket seal, so I would suggest by looking at valves (next post photo) I dropped the washer into the inlet manifold and over time it has been sucked in and caught on the value. And whilst sitting at upholsters for past 5 weeks it has fallen into the cylinder.

Now to clean all gasket surfaces and put head back on etc.





Stuart Duncan

With a knock every 10-15 seconds, I would suspect a broken crank from the hydraulic startup.

Modern coolant is not good in parked up engines in my experience.

Safety Fast

Tony
A L SLATTERY

When you look at #4 and #3 valves in photo I would suggest #3 cylinder hasn't had any compression or firing for a while, suggesting the washer was stuck under the valve.

Valves in all cylinders now appear closed equally.

Also attached is a photo of head gasket. Is the burnt oil stain on gasket a problem?

Engine turns over easily and smoothly. I was unable to hear or feel anything.




Stuart Duncan

That No3 exhaust valve looks dodgey/burnt out to me
Question is where did the coolant come from, and
He's fairly grotty inside if that's after a 12 month old rebuild, I'd be checking the valve stem seals are correctly fitted, but looks like you're up for a valve job anyway--the valve probably burnt out from having that leaking manifold gasket previously
Hmm just relooked at the pic of the head and the gasket, the gasket has been blowing from no3 out into the waterjacket, so the coolant probably came from there, actually it's starting to go in a few other spots as well
It looks like there's been a fair bit of rubbish in there under the gasket---everything has to be clean, clean and the gasket needs retensioning after it's first warm up and again later but the main issue is cleanliness, you can't be too clean
willy
William Revit

put a socket on the drive dog and turn the crank back and forth to check the crank is OK. Any noise or slack is a no no.
These engines will happily run with a broken crank at No 1 web, but a mate had his go at high revs, we salvaged the head and nothing else.
Ray TF 2884
Ray Lee

I would be having the valves , guides and seats on # 3 looked at very closely. Also the # 3 rod, piston and bearings should be removed and checked as well
W A Chasser

I agree with Bill - check the valves, especially, by chucking them in a drill-press and seeing if they spin true.

I would also be very certain the head and block surfaces are dead flat. I remove the studs and run a small, circular whetstone over the head and block surfaces, looking for high and low spots.

Tom Lange
MGT Repair
t lange

I would say the washer jammed on the piston top likely stretched the head studs allowing the water into #3.

Check everything prior to re-assembly.

Safety Fast

Tony

A L SLATTERY

I believe Stuart has a set of my super-quality ARP head studs, which can stand up to a lot of abuse without damage. My studs with rolled threads are also much stronger than factory or replacement studs available today. My opinion is that the piston suffered rather than the studs.

I'm glad to see that you have used the correct banana gasket with your round block and banana head. I would certainly replace it.

Tom Lange
MGT Repair
t lange

I worked at a motorcycle shop in high school. We always advised customers to turn the tank petcock off when they parked the bike. We saw a number of bent rods, when the carb float needle would leak gas into the cylinder. Then they jump on the kick starter and would bend the rod! Agree with above- looks like ding in piston, carefully check the bore, etc. George
George Butz III

My first Porsche, a 55 Speedster bought for $350 (I had my choice of three at that price at a junkyard) had a fuel-shutoff under the dash I didn't know about (no manual). I parked uphill one day - the cylinders filled with fuel, and I bent two rods when I tried to start it. It still ran (sort of), so I sold it the next day for $150 back to the same junkyard. Oh, the folly of youth...

Tom Lange
MGT Repair
t lange

All the advice so far is worth pursuing.

A "hydrolocked" (or "hydrauliced") engine, especially one that sandwiched a washer in the squish band, can bend a rod. You can easily check for that by measuring the piston height to the top of the block.

One additional check I suggest is to use a straight edge & feeler strips to evaluate the block deck surface (and head, too, while the tools are out). We kept burning out head gaskets in the widest area, between cylinders 2 & 3. I've also read these engine have a habit of blowing head gaskets there. Bear in mind, this is a supercharged engine run hard (woman driver). Ourschecked out .005" low in the middle of the block. I had the block decked exactly that amount and the pistons are virtually flush to the deck, so approach that carefully if you decide to proceed (which probably isn't in the cards for you). I came close to pulling the pistons to recontour the flat tops but I also love a squish band and left it alone.

It doesn't look like you're issue had anything to do with the block surface, but now's the time to size it up, for piece of mind or just to keep an eye on.

JIM N

The staining between two and four is somewhat indicative of a leak. No damage to the gasket is visible on the pictures.

What caused the leak is what needs to be determined. The washer would have made the noise.
Bruce Cunha

Stuart, just to sympathize and let you know that you're not the first to have something sucked into the motor, the following is from the 2014 archive:
https://mg-cars.org.uk/cgi-bin/or17?runprog=mgbbs&mode=archiveth&archiveyear=8_2014.dat&access=&subject=8&subjectar=8&source=T&thread=2014091615331219727

Jud



J K Chapin

Hi all, many thanks for your comments.
I had already decided to take the head back to the machinist to check valves and seats (especially those in #3 cylinder) and the flatness of head surface, on Tuesday, after the long weekend.

I have checked piston heights: 2 & 3 are the same and so are 1 & 4. All just shy of top of block. I will check with feeler gauges on Monday and also buy a socket for dog nut and check crank for any rotation roughness. Concerning cleanliness of surfaces, both I and the mechanic were meticulous on that during the rebuild.

I will also do as Tom suggested and run a wetstone over the block surface, plus use a straight edge to see if there are any hollows or raised points, especially around stud holes.

Yes, the engine block has Tom's ARP head studs installed in it. (just checked paperwork and engine was rebuilt 3 years ago, not a year ago. How time flies!!)

Stuart Duncan

FYI - Close up of cleaned up #3 piston

Stuart Duncan

Those chewed-up marks on the upper right of the cylinder are odd. Are there similar marks on the edge of the head gasket?
Bruce Cunha

Bruce
If you have a look up at the top rh corner you can see where the gasket has been blowing accross into the water--i reckon that's where the coolant came from-----and the burnt exhaust valve there as well

William Revit

Unfortunately, all the rough spots on the piston top will create hot-spots, to encourage run-on - not ideal.

Tom Lange
MGT Repair
t lange

Just wondering, does the damaged piston require replacement?
gl rombough

What was keeping the engine from rotating with the crank handle? I don’t see anything in the photos that would have stopped it.
Gene Gillam

Tom, I was also wondering about rough spots and subsequent hot spots on piston top. I am undecided whether to use my dremel to smooth these out or replace piston which will require removing engine from car.

Gene, I think when the piston went down the washer ended up against the cylinder wall and when piston came to near the top, the washer was vertical and became squashed between piston and the head, and the piston was not able to complete its upward compression cycle.
Stuart Duncan

I'd have some concerns about thin, sharp edges on a high compression or supercharged engine, as the pistons in the photo. They run up to, and sometimes into engine knock.

Unless you race your YT or have a supercharged engine running on regular gas (like we do), I wouldn't worry about it.

I'd probably smooth it down with a flapperwheel for some peace of mind.

JIM N

There is no way I could be confident that the ring groove in that piston has not been compressed. Pull the donk, strip it and evaluate the full extent of the damage sustained.
G Evans

Stuart,
I replaced the pistons on my engine without taking the engine out. They come out the bottom not the top as the conrod is wider than the cylinder. I believe it depends on the overbore size of the piston.

Regards
Declan
Declan Burns

These pistons are quite robust and the top ring groove is a fair way down, I doubt that the groove has been pinched up- you can check by pushing the piston over one way and look down the bore with a good light or check with a feeler to make sure the ring is staying on the bore then push it back the other way and check there as well
I've seen plenty worse than that, that were still ok---If the ring is ok and staying on the bore when you move the piston, just knock the high spots off flush to the top of the piston and forget about it,
willy
William Revit

Stuart, thanks...makes sense.

Gene
Gene Gillam

From your description, to me, it didn't hydrolock but the washer was responsible for seizing it. It is VERY unlikely the rings or lands would've been damaged by coolant.

If you really want to examine them, you can drop the pan, remove the con rod cap and drift the piston & rod up . Grab the ring compressor, slip it back down and button it all up.

I just happen to do that a few weeks ago while a head was off.

JIM N

Loving the confidence that the piston has retained its shape. My suspicions are based upon experience, I had an air cleaner nut come lose and end up on top of a piston on my Austin Healey. when the piston was removed it had severely compressed ring grooves. Admittedly a nut is considerable thicker than a washer and I had driven the vehicle over 200Kms, I would still have my suspicions.
G Evans

Thank you all for your comments and suggestions, very much appreciated.

Update:
Cylinder head company has got back to me, they had to replace an exhaust valve which had a slight bend, otherwise all good.

When I dropped off the cylinder head, I showed him a photo of the piston. He suggested smoothing off the roughness which I have done with a Dremel stone bit (see photo). I still need to smooth off the cylinder edge (top right).

After looking at head gasket, he suggested I tighten the head nuts with a bit more torque, as the gasket showed it was not tight enough. He stated:- ensure the engine is hot when tightening the head down.

I felt around #3 piston with gauges and it was even. I could get the 0.025" gauge down but not the 0.030" guage. Gauge was hitting aginst the ring all the way around.

Whilst turning the crank in reverse, I felt nor heard anything different during the rotation.

I purchased a 400mm steel ruler and checked the head for flatness by shining a bright light against head and ruler - no light showed under the ruler, no matter where I placed the ruler. I noticed the pistons protrude about 0.02" or less above the block surface.

I have been one very lucky owner. The only cost will be the checking of the head and valve replacement, as I have spare gaskets. Now to collect the head, reinstal it, etc ensuring I do not drop anything into engine or manifolds, and start up making sure head is tightened down with the correct torque. AND LISTEN for any unusual noise. THEN frame the "squashed washer" as a reminder what not to do.

I will do compression and leak down tests once head is installed.

Again thank you
Stuart


Stuart Duncan

This thread was discussed between 02/04/2021 and 06/04/2021

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