Inlet manifold & thermostat anomoly

[Pirate]

Hi all,

I know the discussion surrounding Mk1 & Mk2 inlet manifolds & thermostats has been covered many times on this forum, however having read the thermostat article in this months mag I thought it was time I should check it, as it has been some time since I fitted it and I've always had a niggling doubt whether it had the bleed hole in it.

Anyway I've always assumed I have the Mk2 manifold as it doesn't have the raised studs either side of the stat housing, and sure enough I had the Mk2 thermostat fitted with the foot (and I established it had the bleed hole).

HOWEVER, from the article in the mag showing the stat housings, it appears I have a Mk1 stat housing without the water bypass passage. If you look at the photo you will see this, and also see there are no raised studs per the Mk2 manifolds (top right of the pic just in front of the bolt is a circle with 'P' stamped in it where the cut-off studs normally are), so I guess as my car was registered April 1972, this was manufactured part way through the change of production. Following a search on the forum I could only find reference to Mk2 manifolds on a Mk1 engine and vice versa, but nothing about what looks like a Mk2 manifold externally, with a Mk1 stat housing and no water bypass.

IMG_1856.jpg

Having measured the internal depth of the stat housing, and the total length of a thermostat with a foot, it does look like there is about 5mm of clearance for the stat to open, but is this enough or should I really be fitting a Mk1 thermostat without a foot?

LD parts website suggests that the thermostats with foot they supply are suitable for all Stags, however I have read elsewhere that if there is no bypass hole for the thermostat shaft to slide into, the longer thermostat with foot may not be able to fully open.

I'm sure this question has been raised before, but following the useful article in the magazine its probably an opportune time to raise it again!

Your advice much appreciated!

Thanks, Jeremy

[Lingen]

Jeremy. Having written the article in the magazine, I can add a bit more information that I have come up with as a result of your questions. The Mk 2 thermostat that I have now measured is around 33mm long (closed) from the top disc to the spring loaded foot. If this is fitted in to a Mk 1 manifold, it will bottom out on the inside of the casting, well before becoming fully open. This will almost certainly cause overheating problems. With the Mk 2 manifold, the hole in the inner casting is smaller than the spring loaded disc that closes it off, but the rod to which it is attached can continue to pass through the hole in the casting, which will allow the thermostat to continue expanding till it is fully open by compressing that spring.
For this reason I think it would be unwise to assume that a Mk 2 thermostat will fit any Stag. Its dimensions would need to be carefully checked first. I would always recommend fitting the specific one for the manifold, to be absolutely certain.
Mike.

[Pirate]

Thanks Mike, that was my opinion too having read your article so reassuring to see you agree. I did measure the internal distance to the rear of the housing to be about 38mm so as mentioned it would have opened about 5mm (and there is some movement when pushing the stat open), but presumably this may not be fully open, so I'll stick with your advice and get a Mk1 thermostat.

It just shows how useful your article was for me personally, I always thought I had a Mk2 manifold from pictures posted on the forum in the past, and without your article I would never have realised I needed a Mk1 thermostat!

Thanks again Mike both for your article and your response.

Jeremy

[Ian F]

Jeremy

Means I've got to check mine now! Mine is April 1973, was diabolical with a new Mk 2 thermostat so I reverted to the original one and all was OK again. Maybe now I know why, but I don't want to have to strip it again to check, so I might leave well alone.

what if anything may be the issue of a Mk1 thermostat if I have a Mk 2 manifold?

ian

[Lingen]

Ian. The same thing really, only for a different reason.. A fair amount of coolant will bypass the radiator all the time, which may also cause the engine to run hot.
Mike.

[Westfaling]

It was a really great article in the mag thanks. I checked mine and was surprised to find it has a Mk 2 casting. Fortunately I'd installed (nearly) the right thermostat. So I just drilled a hole in it and put it back - with the hole at the top.
What's interesting is that the car is a Federal Mk1 (1972) and I've no reason to suspect the manifold has been changed. It could be another example of "Mk2" items that were fitted to Mk 1 Federal cars. Other items that come to mind are the engine air intake and the expansion bottle system.
Nick

[elvimto]

http://s903.photobucket.com/user/Malkey2003/media/IMG_2033.jpg.html

This is a MK 1 manifold with a stat which has a jiggle pin if you have a Mk 2 manifold it takes a different stat but you can drill a hole in the stat to get the same effect.

[Pirate]

Jeremy

Means I've got to check mine now! Mine is April 1973, was diabolical with a new Mk 2 thermostat so I reverted to the original one and all was OK again. Maybe now I know why, but I don't want to have to strip it again to check, so I might leave well alone.


ian

Hi Ian,

If it runs at a steady temperature I think I'd leave well alone as whatever you have fitted seems to be doing the job it should. The thermostat is a simple check but also a messy one! I only checked mine as the temperature started to creep up slightly on a run and I had a doubt about which thermostat I originally fitted.

New Mk1 stat now on order so I'll see if it makes a difference once it arrives.

Elvimto - your photo shows clearly the raised studs I mentioned on a Mk1 manifold which mine doesn't have, so in my case I'm pleased I have now also checked the thermostat housing.

Jeremy

[Westfaling]

Interestingly I just refilled the cooling system after an engine rebuild. Normally I have to top up the system a couple of times after running the engine. With the hole drilled in the thermostat it seemed to fill in one shot.
Nick

[Pirate]

Just to conclude my initial query, Mk1 thermostat fitted and after a 100 mile run at the weekend including 15 minutes stuck in traffic, winding gradients over the Horseshoe Pass and motorway speeds back down the A55, the needle never budged above the halfway mark.

So, if your car is running above halfway but not worryingly hot, before calibrating gauges and changing senders check you have the correct thermostat fitted that can fully open when hot!

Thanks for your advice Mike,

Jeremy

[Registrar]

An old post I know but let's just clarify the situation of mk1 / mk2 inlet manifolds. This change in the inlet manifold was not a change made at the mk1 / mk2 change point i.e. LD20001 and engine LF/LE 20001. The change was made in the States at LE 10001 E (i.e. 1972 model year cars) and in the UK and Continent at LF 11429 (H)E i.e. at cars made around February/March 1972. so let's stop talking crap about mk2 parts being put on mk1s and vica versa. If you bothered to check the relevant parts manuals, the information is all there.

Sorry to be grouchy but if we stopped using the made up Mk1 / Mk2 term and started to use the correct Triumph terms i.e 1971 model year, 1972, model year etc. then people wouldn't get quite so confused. Alternatively, try reading the relevant Triumph produced literature as the answers are mostly in there somewhere.

Peter

[sujitroy]

I haven't got my mag. yet, but I created a poor qualify YouTube video showing the manifolds, early verses later, side by side.; https://www.youtube.com/watch?v=Rd9UVjCNP8M&t=25s

Sujit

[Wheelz]

I ran my car for some years with a Mk1 type inlet manifold, with no sign of an overheating tendency, and I am sure many other cars run perfectly well with it, yet there is a permanent bypass to the radiator which you might assume reduces the cooling margin to some extent albeit, apparently by a negligible amount.

But someone raised an interesting question as to why they changed it on the Mk2 system? Was it a desperate move (along with any other changes) to try and cure the overheating problems that some cars exhibited?