XJ6 Series 3

I have had a problem recently with coolant loss.

Today discovered that coolant is getting into the inlet manifold. The rubber pipe from the manifold plenum drain developed a slight split and I found coolant leaking out after a short period of running the engine in the carport to check something else. Having run the engine a couple more times to investigate I find that about 10-15 minutes after turning off the engine, some coolant seems to collect in the manifold

I am thinking this must be from a gasket failure between the cylinder head and the manifold. I can’t think of anywhere else it could get there from, apart from the throttle body which has coolant feed, but I don’t see any evidence of a leak there when looking down past the butterfly.

I’ve just ordered a new manifold gasket, but would appreciate any contributions from members if there might be any other areas I should check. I had the cylinder head off about 6 months ago for valve replacement and the manifold gasket was renewed at that point….perhaps I didn’t torque it back adequately?

 

What year Series 3 ?
The 4.2 long stud engines were notorious for cracking between the bores and causing HGFs, (my 1980 Series car suffered this). Only cure is to fit top-hat cylinder liners so the crack is covered. Later blocks had the narrow slots cut, with no liners and the head gaskets last a bit longer, but eventually fail. The slotted block was essentially a spatchcock to get the engine a few more years before the aluminium AJ6 engine replaced it. Even these used to ocasionally suffer HGF !! ONe clue is to check for pressure in the coolant passages when the engine is cold. There should be none at all.

The other place to look you have already identified, namely the gaskets on the inlet manifold to head, and also possible the water rail on top of the manifold.

Is the engine oil OK ?

 

I have ths rather uncleqr memory of a coolant line to the intake to heat the mixture. You mihgt cap mit off and see if the manifold continues to collect coolant/

Carl

 

I had similiar issue and the oil was milky all of a sudden with a lot of coolant loss. My mechanic found a leak at front of the engine block in the timing chain cover .
My mechanic thought this was the cause as the coolant leak was severe and he felt ahead gasket it would have not accumulated so much coolant quick in a short time. He welded the leak up and 4 months later still going well, slick coolant loss but oil no longer milky.

 

The car is an ‘85 model and has the slotted block. There is no sign on contamination of the oil so I don’t think it’s a head gasket failure. Head was off earlier this year for new valves to be fitted so it had a new head gasket at that point.

Is the coolant passage in the throttle body a know problem area? Is it designed to heat or cool? I am using the car in a tropical climate where we never have cold weather. The heater is not connected.

I haven’t begun stripping down yet as the car is booked into the body shop for Monday morning for some minor paint rectification work. I’ll get started on this when it returns.

 

Presumably with the head taken off, all the related gaskets required for the job were replaced, correct ? It does sound as if there is a leak on the inlet side somewhere.

 

Yes I used a set of new gaskets when reassembling after doing the valves. Perhaps I didn’t torque down the inlet manifold well enough as some of those nuts are very difficult to access.

 

1. loose bots can be the issue!!!

2. in that clime, you can get along just fine sans the pipe to the throttle body. it is intended to warm the mixture and make the car more responsive in cold weather.

In take heaters have been around for decades. many hace defeated them for the same time.

Carl

 

This morning I drained the coolant and removed the loop through the throttle body. Replenished the coolant and took for a test drive. After cooling off again I checked in the intake manifold and the problem remains. There is a pool of coolant in the manifold.

So next step will be to remove the manifold and check the gasket. That will probably be a week away as the car is going for some paint rectification on Monday

 

The head does have to be retorqued after a gasket change. I can’t remember the interval but I would guess 2500 miles or less.Check with your mechanic,

 

I did re-torque the head after about 500km of use following the valve work.

At present, I do not think the head gasket is giving a problem. The coolant is appearing in the inlet manifold, and that doesn't have anything to do with the block-to-cylinder-head joint. It surely must be the cylinder-head-to manifold joint, or possibly a crack or other fault in the inlet manifold allowing coolant to get from the water rail to the manifold plenum. If the head gasket were at fault, the coolant would be getting into the bores or the oilways, which it does not appear to be doing as far as I can tell. There is no evidence of contamination of the oil. The engine must be ingesting coolant and burning it off, as the coolant level does gradually drop.

If the car were not booked into the body shop tomorrow, I would have removed the manifold today, but as it is still drivable and the body shop is only about 500m from home, I'll get that work done first and continue with the investigations next week. Meanwhile my new gaskets are on the way from SNGB and should reach me by middle of the coming week. Just hoping it is merely a gasket problem and not a fault with the manifold as it might be tricky to find a replacement one here in Thailand.

 

I once managed to trap an intake washer between the face of the manifold and head.

Those washers are quite thin, but it leaked as soon as I added coolant.

You can JUST get the nuts off, if you have a hoist, and pull the manifold back enough to check.

Using a small magnet to position the nuts and washers during reassembly helped.

Please post your results,

Rob

 

Yesterday morning I got the intake manifold off. It was siezed on and took a lot of swearing to shift it.

I couldn’t really tell if the manifold gasket had failed as it tore on removal and left bit on both faces.

I bought an endoscope that links to the phone for a screen and had a look inside the manifold and the cylinder head inlets. Could not see any sign of any cracks or holes that could be causing the leak. It’s all back together again now, but I plan to add some “stops leaks” fluid to the coolant before starting up again. Couldn’t find any in town so had to order some from the city yesterday. Will report back after it’s tested.

If the problem remains, I’ll be taking the cylinder head off next, although I can’t really see how a head gasket failure could result in water in the manifold.

 

Test the intake on the bench for leaks. either with liquid, air or vacum.

Any connection of the water rail and the intake.

Any signs of liquid in the intake ports on the head. head cracked in an intake port. possible.

Sealant, NO. Invited other issues.

!!

Carl

 

I couldn’t think of an effective way to test the manifold for leaks because it has so many orifices that would need to be somehow sealed and the thing filled with water. Any suggestions on how to do that would be appreciated.

I forgot to mention that before removing the manifold, I discovered the problem had worsened as the oil has got contaminated with coolant and gone milky. Is it possible that this can happen if coolant is drawn into the combustion chambers, or is that a sure sign of head gasket failure?

Today I ran the engine again a couple of times and so far have not detected any more coolant in the manifold. I changed the oil and filter but after running the oil is milky again. I was wondering if this could be due to residual contaminated oil which didn’t drain from the oil cooler etc affecting the new oil? Opinions invited.

Before filling with coolant and running the engine I did a compression test which was normal.

I still cannot think of a way that a head gasket failure could result in coolant pooling in the manifold, so I am delaying pulling the cylinder head just now.

 

Milky moussey oil is a sure sign of head gasket failure.

 

I just found this quote on another motoring forum:

“Milky, frothy oil on the dipstick could mean you have coolant leaking into your oil pan, but doesn't necessarily mean a bad head gasket. This symptom is too often mis-diagnosed as a bad head gasket with unneeded repairs performed. There are many other things that can also cause this and it is rarely a headgasket. The majority of head gasket failures do not show this symptom. This usually only happens if coolant collects and sits on the piston and hydro-locking usually occurs first if this is happening.”

In my case, coolant has been collecting in the manifold and could well have got sucked into the combustion chambers and ended up sitting on the piston.

So is it likely / possible that coolant pooling in a combustion chamber can leak past the oiston rings and get into the sump?

I also read just now that, after getting contaminated oil, it can take 3-4 oil changes to get rid of the milkiness.

Comments invited! I can change the head gasket if that is what is required but it is a lot of work if that might not be the problem. Just trying to get as much info and opinion as possible before I steam in there. (It is a big job)

 

Andy
A head gasket can fail between the oil passages and the coolant passages, but that does not necessarily mean the compression of the cylinders is affected if there is no failure in the sealing round the cylinders.

As far s I know, coolant in the oil means a head gasket failure, as the join between the block and the head is the ony place this can happen, absent a coolant/oil type of oil cooler.

 

1/ although a leaking intake is now the ess likely cause of coolant loss, i offer the following. On the bench. Support it as level as possible. ports up. Plug all other orifices. Fil;l with a colored liquid.to the top of the port. Observe. Any loss and any pooling under it Similar to the way to check a head on the bench for leakig valves.

2. I can envisage a head gasket failure. Coolant enters the combuation chamber. some can get passt the rings and enter the sump. And/or some can leak from thje combusation chamber oin to the intake via the intake valve. Any that gets past ans exhaust valve gets atomized and not noticed.

Bottoim line?

Teh head gasket has failed....

Sorry!

Carl;

 

Thanks for the input from all so far. Here is today's update:

I changed the oil and filter again this morning and went for a test drive. Car performed well in terms of responsiveness etc and engine ran smoothly. On return I let the engine cool off and checked the oil. It is staying clear, so it looks like the coolant contamination is not ongoing.

However, I just had a look into the intake manifold and there is a large pool of coolant in there again, so the original problem remains.



Tomorrow I plan to remove the manifold again and do a fluid test on it, following the lines suggested by Carl in the previous thread. This sounds like a good idea, and I reckon I can block up the other holes to check for water-tightness. I still think the problem is most likely to be in the manifold, as I cannot see how water in the combustion chamer could get sucked into the intake manifold, as when the valve opens, the vacuum is in the cylinder drawing inwards. It could, however, be a fault on the cylinder head at the intake port admittedly. I can't see this being caused by the head gasket though, so will not yet remove the head until I have evaluated the manifold more thoroughly.

I will report back once I have the manifold off again and bench tested.