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MG Midget and Sprite Technical - Oil in coolant; recent valve job

Background info:
1967 1275 midget blew head gasket between No. 2 & 3, so I removed head (engine out to braze crack in timing cover), and had resurfaced by competent machine shop (30 yrs experience, has done similar work on DOHC Subaru for me in past). He also installed hardened exhaust seats, and said that the head did not need any other parts, save for rubber valve stem seals). Receipt says he checked for cracks.

Cylinders looked very smooth and unscored, so removed studs and cleaned up deck w/red (very fine) Scotch brite pad. Studs and nuts in great shape, so cleaned and reinstalled.

NOTE 1: was not able to determine flatness of block with my lousy straight edge, but machinist said it's rare for these blocks to have problems in this regard, so I did not lug block to his shop for resurfacing. (Might as well rebuild at that point, and oil pressure is still great on this engine.)

Used correct part no. Payen black head gastket (Hap's suggestion), with light, even coat of copper spray sealant (NAPA), then torqued per proper sequence, using this method: all up to 25 lbs. in two stages, then large nuts up to 50 lbs. in two stages. Re-checked all nuts in sequence.

Set valve lash. Rinsed out block until water ran clear, installed engine/tranny.

NOTE 2: moved temp sender to head, in order to put electric fan switch in bung welded to side of Speedwell aluminum radiator's top tank (original location).

NOTE 3: thermostat is 180 deg. and water pump is newer version (says 'County' on side) with larger impeller.

Symptoms:
Engine started instantly, ran fine (after re-setting timing and carbs). BUT car runs a bit warm at speed, 190~195, and coolant is muddy.

Questions:
(1) How much higher, if any, is reading on temp gauge with sender in head? Fine with me to return sender to radiator, if need be.
(2) I see that Deborah and Hap say you *should* re-torque head as matter of practice. Will 1275 head that *does not* get re-torqued leak, such that oil will get into coolant?
(3) If I re-torque (as I did early this a.m., after car cooled overnight), has head gasket been ruined by leaking due to failure to re-torque? (If indeed this is what happened.) Must I R&R head again?
(4) Am I missing anything else obvious?

Thanks for your help,

Joel Young.
JM Young

Joel

The black payen HG does not need anny aditional sealant!
And does not need to be retorqued.....
This is a point that can be discussed as intesifly as fire arm posesion or faith so do what suits you and live with it

Temp sender in the head shows a higher tem than in the rad but this is no problem as all the later 1275 had it fitted there!

I would flush the coolant and drive it
And as long as it does not boil it is fine

Fitted the correct boss for the tempsender in the head?
Onno Könemann

Joel. Thermostats operate to the "rule of 20"--i.e. the thermostat begins to open at the rated temperature and is fully open 20 deg F later. With your 180 deg thermostat, your readings of 190-195 are to be expected. In fact, the thermostat has not even fully opened at that upper temperature. Consider, also, that the ambient air temperatures are rather high, often over 100 deg F which means that the surfaces you are traveling over are closer to 140-160 deg F. Yes, even with a 160 deg thermostat in place, I would expect your engine to be running at, or near, the temperatures you are recording.

Good thing. Higher engine temperatures, with good quality oils, result in less engine wear and longer engine life.

Agree with Onno that the Payen/Fel-Pro resin gaskets should be installed dry. But, this does not mean that you have ruined the installation. Drive the car some, look for leaks from the head gasket, and see what happens.

As to the "muddy" coolant, what are you running in the cooling system? Did you flush the cooling system before you removed the cylinder head and replaced the gasket? Sounds to me like you had some build up (rust) in the system which is being flushed out by the new coolant. Oil will show up as either particles of oil (beads) on top of the water in the radiator or as an oily foam in the filler neck of the radiator. Neither of which you seem to have noticed. Hence, my suggestion that this is most probably old residue from the cooling system not being drained, flushed, and refilled every two years in the past.

Les
Les Bengtson

Joel -
Send me an email, request "Boltbabble"

FRM
FR Millmore

Onno,
Yes - installed the boss for the sender, I presume it's intended to prevent bottoming out (thanks for asking).

I hear you on the debate over retorquing. Threads and texts seem pretty evenly split, and no-one has said it's damaging, so thought I'd at least try.

I did read that Payen gaskets do not require sealer (good to know that Felpro is an option, Les), but also have seen racers logging onto these threads who regularly add either copper coat or 'hi-tack,' and haven't heard that it hurts. So, went with 'belt-and-suspenders' here, too. Next time, I'll save a nickel on the can 'o copper coat.

Good to know that a head-mounted sender is OEM for later 1275s. Have you ever experimented to see what the temp drop is from there to the R/H top tank? Just curious, and don't have an infrared thermometer. I am trying to figure out the right temp switch range--and here, I merge into Les's comments on thermostats.


Les,
The 185 on/175 off fan switch (Painless brand) seems to come on fairly late, but since I moved the sender simultaneously with installing the new switch in the radiator, I don't have a precise frame of reference. I am now beginning to wonder whether--given what you've said about the 'rule of 20--it might make sense to go for a 160 thermostat. My thought was that, even though the 160 thermo might still have the engine running around the same temp once fully open (which you point out may be healthy for the engine), the flow rate would be greater through the fully-open 160 thermo roughly 20 degrees earlier. Perhaps more flow would cause the fan switch to kick on earlier in stop-and-go. The Painless switch has a flat front--not an elongated probe intruding into the flow like the gauge sender--and sits at the end of a boss identical to the one mounted in the head, so perhaps this is a faulty hypothesis.

So far, no external leakage at all, but the initial run was only 10-15 miles round trip up the freeway and back. I didn't mention the foaming at the radiator neck; it is very slight but present. I drew a sample to let it settle overnight in an old glass. Today, there is a small rainbow swirl on top (teensy oil slick), but mostly a brown muddy sediment on the bottom that readily suspends in the solution if you stir it, but precipitates out of suspension fairly quickly. I did not flush the block under pressure; was trying to catch everything, as our storm drains go straight into the Rio Grande. So, just poured a couple of gallons in through the heater tap and out the water pump *after* installing the new head gasket and before reinstalling the drivetrain.

NO doubt that this engine was not regularly flushed; my first post last year characterized the purchase as a 'rescue,' and I stand by that description. However, the ex-owner evidently didn't have the incentive to open his tool box long enough to damage this tough little motor. Maybe it's just r-e-a-l-l-y dirty. At any rate, I guess next weekend I'll back-flush her under pressure, and try her again. I guess I'm just afraid of overheating and warping the head.

FRM - will do, thank you.

Joel.
JM Young

Hi Joel,

Can you post a link to the debate(s) regarding re-torquing heads please. I'd like to read them.

As regards using glue on the head gasket, maybe it actually degrades the HG's ability to create a decent seal rather than enhance it.

I asked this question recently, and nobody who replied said you sould use glue on the Payen black, or on any head gasket, and that is what I have always believed and followed.

So could you also post the link(s) to the arguments in favour of Head gasket sealant/glue as well?

Thanks.

Lawrence Slater

I, too, was not aware of anyone advising additional sealant on a Payen black gasket - having "done my head" recently, I researched this quite a lot and could find no-one recommending that, since the whole point of the black gaskets is that the have the black (elastomer?) material to make the seal tight.

As for re-torquing, I can't point you at any specific debate (maybe try mini forums, they're usually good for that kind of debate :) ) but I wouldn't think that the head gasket choice would be the only contributing factor to the question of retorque or not - I would expect some stretch in replaced studs, for example, that even if the gasket clamps down in one torquing up could mean that a retorque would be required.

There are some very experienced and well respected engine builders on here, so it would be good to hear from them.

OSM.
OrangeSpyderMan

Yep and those exelent well respected engine builders do not agree on this point.

The only HG I blew that I fitted my self I did not retorqe.
Though blowing out between 2and3 on a 1380 that had run slightly to hot is not a big surprise ;)
Onno Könemann

I resenty retorqued my head on the new engine after the 1st good hot run of 50 miles I had with the bonnet on, and they were all off to the lightter side by 5 psi

So im now a fan of retorqueing,,,,like you said, it cant hurt, now looking forward to doing my valves in another 300 miles

Prop
Prop

Lawrence,

Here are a handful of the debates on retorquing that I've found (there are dozens if you Google the subject):

http://www.mgexperience.net/phorum/read.php?1,942931,943188

http://www.british-cars.org/mg-midget-sprite-technical-bbs/1275-a-series-head-bolt-torque-values-201003171902523746.htm

http://www.mgexperience.net/phorum/read.php?3,1716414

Here's the string where Hap (racer/engine builder) suggested that "Coating the black composite head gaskets is not necessary per instructions, and works most of the ttimes, but when I use that head gaskets on the race cars, I use Permatex Hi tack spray on gasket seal on the composite gasket, never had a head gasket failure with that set up."

http://www.mgexperience.net/phorum/read.php?3,1572073

At any rate, I'll update you guys whenever I have time to get back into the garage and see what's what. If it's actually harmful, as opposed to merely redundant/unnecessary, I certainly want to know.

Joel
JM Young

10.000 Mls 1360 engine driven spirited: no re-torque, no problems.
Alex G Matla

Thanks Joel,

I'll have a read through later.
Lawrence Slater

After recently having my head skimmed, I refitted it and torqued it up to manufacturers spec. Having read a recent post on here by Fletcher Millmore, I ran it up to temp then re-torqued it hot. Drove it approx 500 miles and came to re-torque again cold. I was surprised to find that when I went to back off the nuts before re-torquing, the first two were quite slack, which didn't fill me with much confidence, so I nipped them up again, ran it up to temp and re-torqued again which felt better. BTW. I didn't and never have used any kind of sealer or "Pig snot" as Prop would call it. so far, so good after another 150 or so miles.
Any thoughts?

Bernie.
b higginson

Bernie -
Typical, and why I retorque. I have sometimes seen HG leaks (cyl full of water) after one heat/cool without retorque. Far better to waste a few minutes than have to replace the gasket again. CI heads hot at least for first retorque, alum heads always cold.

I've said numerous times, some quoted in links from Joel above, that mileage is a surrogate for time and heat/cool cycles. If an engine sits for months or years after rebuild, even not run, the nuts will be loose. I retorque such before startup, when first hot, next day, after a hundred miles and/or several heat/cool cycles, at 500 miles, 1000 miles, a year, then about every two years.

And lest you doubt, back off each nut a bit before retorque, each in turn. Putting a torque wrench on a nut that does not move at all means nothing - it could be 50 % below what you have the wrench set at; this depends on the nut/washer/thread condition and lubricant used.

Simple test is to put witness marks on each stud & nut and the head, retorque, and see how much it moves. More than about 15 degrees means you should have checked it sooner. After torquing as stated above, I have checked cars (MGB example here):
"retorque head – all nuts moved ap 10-15deg RH rear & Rear-cent ap 20-25deg; Since install = 2250mi, 13mo Since last retorque = 1750mi, 11mo"
"July 09 check: retorque head – nuts moved ap 5-30 deg; Since install = 5200mi, 6yrs; Since last retorque = 3000mi, 5 years"

Suggest Alex try this and report!

FRM
FR Millmore

Hi all,

I've been reading all the stuff I can find about this torquing business. And there are definitely two camps out there.

If we assume that the standard studs are being used, not the more modern stretch bolts/studs. ----

After the first torque to makers specs,

One camp says, emphatically, torque COLD.
One says torque HOT.

Both have persuasive points on their side.

Is it possible that both are right?

Surely this can't just be a matter of opinion can it?

Aren't there conclusive facts/arguments/documents that dictate which is the correct procedure?

I always understood (perhaps wrongly it seems), that an iron head was torqued again after it got hot, and an ally head had to be allowed to get fully cold again.

I'm going to try getting a definitive answer if that's possible from various HG makers to see what they say about their own gaskets, and it's torque requirements.




Also, I have found that to use sealant on a modern HG such as the Payen Black, will degrade the surface of the gasket, because of a chemical reaction with the coating on the surface, that is specifically put there to aid achieving a good seal. Hence using a sealant unless it is included by the gasket maker will adversely affect the hg's ability to make a permanent seal.

and yet people report getting good results using a sealant. Again, I'm going to ask the makers for an opinion.


Lawrence Slater

Hi,

Dealing with coolant systems that are full of sediment, it can be a long drawn out process of flushing/running many times until it starts to clear up. You wonder where the stuff comes from. I just went through this with my Durango. The guy who owned it before me had mixed coolant types and there was a never ending supply of brown fine sandy material that would float to the top.Eventually after probably 10 or so flushes it was clean. Like you, I suspected head gasket issues, but it wasn't. Doubt yours is either.

Alan.

A Phillips

Maybe I will Fletcher. First replace the engine from my Volvo though.
Alex G Matla

Joel,

I had similar issue after I rebuilt my 1500. I out it together using a block that I had the cylinders checked for bore size and taper but did not get it hot tanked. After installing, it ran hot and the water was quite brown. I ended up putting some radiatoer flush in and running the car for 2-3 days like that and then flushed it again. The amount of rust and crud that came out was amazing.

I also usually run straight water in the cooling system, draining it each winter and filling the heater with RV antifreeze (non-toxic). This has always worked well for me and it does get very cold here in the winter. Living in NM, f you are not subject to freezing temps, you could probbly run water with a bit of water wetter and maybe some water pump lube mixed in. This way, if you do need to drain the coolant, you need not worry about environmental impact. Also, no need to worry about any pets ingesting anti-freeze. That's the main reason I do this. We had a dog that got into some and it came close to killing him..

Deb Evans had a very good explanation why you should always retorque cold. If you retorque hot one time and then cold the next, your values will be way off. I've always done retorque cold since you are dealing with a more consistant temperature of the engine. If you retorque hot, the engine is cooling while you are working on it so your values will not be consistant.

Good luck and let us know how everything ends up.
Tim Michnay

Tim,
What product did you use for the rad flush?

There are various here in the UK, whats the verdict on these? Which is likely to be the best product in our old brass and iron mix coiling systems?

re-torque
I've emailed various head gasket co's but so far no reply about there preferred method.

If the cold method is the best for retorque, where has the disent come from?

I have to admit, that after all the years of following the hot torque procedure, I now have doubts about which way to do it.

Maybe it doesn't matter which way? is that possible?
Lawrence Slater

Lawrence,
I used Prestone flush. I usually try to go with a name brand on such things since the quality should be the same throughout the product line. So far, I've had no ill effects from using it.
Tim Michnay

Re hot vs cold retorque:
The thermal coefficient of expansion for the usual cast iron is about 6 x (10{to the minus 6}/in/in/deg F). The coefficient for carbon steel (studs)is almost exactly the same. Any difference is indiscernible in the variation of the precise alloys of these materials; high alloy versions may vary somewhat, but we do not have those here.

Consequently, any changes in clamping of iron heads with normal temperature change, from "room temperature" = "cold" to "operating temperature" = "hot", are insignificant in workshop practice; you could torque hot or cold or in between. In fact, my "hot retorque" is usually 15 or so minutes after a road run, since it is just too unpleasant to do it "HOT". The temperature change over the less than 5 minutes it takes to actually perform this has no effect whatsoever.

Aluminum has a coefficient around 12, but the bolts are still 6, so we have a different situation. Here, as the temperature increases, the head expands much more than the bolt; the bolt restrains the head from actually expanding so much, but the clamping loads and stresses in the parts go up a lot. It is primary that there must be sufficient clamping to always prevent leakage, so torques are specified cold, and we have to trust the designers to ensure that stresses do not go too high when hot. This is why alloy head (cold) torques are often less than the same engine with iron heads.

For alloy heads, the differences at varying temperatures are sufficient that definitions of "cold" become important. There is as much temperature change from "dead=of-winter cold" 0 F to summer 100 F as there is from "summer cold" 100 F to operating 200 F, and you must deal with it. I have seen a number of engines with alloy heads begin leaking in very cold weather, only to evidently "heal themselves" in more moderate conditions. These gaskets will eventually fail; my procedure is to torque them to somewhat less than the book "room temperature" torque spec when very cold.

All the following re gasket flow still applies to alloy heads, but you can't torque them hot. My procedure on first run is to retorque as soon as they are "cool", say 100 F, to prevent coolant leakage, then redo when down to room temperature.

The reason for hot retorque is that the sealants on gaskets, and the binders in composite gaskets, flow under pressure; and, they flow fastest at higher temperatures, with the greatest flow on first pressure and first heating. This flow will result in loss of clamping once hot, and greater loss after the time it takes to cool. As stated previously, I have seen serious gasket leaks on engines where the gasket is replaced, brought to operating temp, and allowed to cool without retorque. Allowing sufficient time between gasket fitting and final torque before start will avoid this, but it will still lose clamping after being hot. The hot retorque will compensate for initial flow and assure that there is sufficient clamping to prevent leaks after cooling. There will be more settling with the passage of time and heat/cool cycling, hence the following retorques as stated previously.

So called "no retorque" gaskets are sufficiently stable that the flow and clamping loss is not as fast or severe, but it still happens. Payen gaskets do lose clamping and will leak after sufficient time. I've measured torque and nut movement, and I've replaced plenty of leakers.

I have retorqued plenty of "no retorque" gaskets on many types of engine and found the same movement of bolts. Recently I stopped head gasket oil leaks on a couple of my Mazdas, which were in the 15-20 year old 120-150,000 mile range, with "no retorque" gaskets; fortunately, I did these retorques before the gaskets failed in a more critical way.

Some gaskets are more stable. Single layer steel shim gaskets with a thin sealant might actually get by without retorque after the first one, but they are fussy, and I think not used much today. Multi layer steel gaskets are better, but they still need it at intervals. The Mazdas are this type.

It is always highly desirable that heads be tight enough that no coolant ever seeps past the gasket, as that diminishes the ability of the gasket surface sealant to do its' job. Failure to retorque soon enough will result in such seepage and eventual failure. Evidence of seepage can readily be seen on metal faced gaskets as dark stains, but this is difficult to see on fibre faced gaskets.

The gasket manufacturers put a lot of work into making the gaskets stable, and the car makers buy it, so long as the thing gets past warranty. People who build race engines take them apart for other reasons long before the better gaskets start leaking. However, if you expect your engine to not ever need a head gasket - as I do - then you retorque on a schedule similar to mine. See previous post - it works.

FRM
FR Millmore

FRM: Arguments based on figures! I like that.
J.W. Vlaanderen

FRM,

Thanks for that truly easy to follow and very comprehensive explanation.

I always believed hot for iron and cold for ally. That was what a RR mechanic told me almost 40 years ago. So thanks for confirming it with such a detailed argument.

Tim Michnay,
thanks for the tip about prestone flush, I'll look for the equivalent here.
Lawrence Slater

This thread was discussed between 08/08/2011 and 18/08/2011

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