95 Jaguar XJ6; ran a cold compression check. Each cylinder has exactly 257 psi. This is the first car i've ever owned that each cylinder had the exact same pressure and yet the car runs very quietly and smooth, yet doesn't have any power. You would expect a lot more pick up than what it has, very sluggish and disappointing.

Do you find it strange that a 95 would have the exact compression in every cylinder and it being high (257 psi even all the way down)? Never seen a car like that!

They have always been a few pounds different. Used two different compression gauges. Please send some feedback.

Thank you!

 

Recently bought this Jaguar and it really look nice but on the way home from buying it: the radiator pressurized. It sounded like it was coming apart, but the temp gauge was sitting in the normal position. I'm a mechanic by trade, but been retired for two decades. This car sounded like it either had a cracked head or head gasket from hearing the radiator run. If the thermostat stuck on it, then you would expect the temperature gauge to climb. But, it stayed in the normal range. I drove the car home. I thought the radiator was going to explode; i was making so much noise.

Removed all of the spark plug and did a cold compression check. All cylinders are 257 psi. I've never seen a car this old with 257 psi even! I suspect the head must be warped and that would cause the cylinders to bypass each other and maybe have the same compression: i don't know. The car certainly didn't have a lot of power for a Jaguar. This jaguar is non-turbo.

Does anyone have any other suggestions other than just pull the head and take a look? Is it possible to put an aftermarket turbo on this engine? I know that there are several Jags that came with a turbo. Is it possible to use the same turbo? I wouldn't know if the valves are different on turbo engine or not; i don't know that much about them and what i'd need to change the head. Also, will a turbo engine make much difference in power because when you see this car: it looks like it should run. Yet, when driven, you feel like you're driving a beetle! Very disappointed i didn't look more closely when i bought it.

If anyone has any ideas on what to do, please let me know. I believe the radiator is pressuring and i'm disappointed in the amount of power it has. I've even thought about pulling the transmission and engine and putting an LS in it with an automatic 5 speed transmission.

Any help would be greatly appreciated!

 

Bob ?

The AJ16 engine as it is factory supercharged has a different head , crankshaft , Mass Air Flow meter , Rear end ratio if not stronger casting , fuel injector size , headbolts , ECU mapping , extra fuel pump , transmission and crossmember , ect . then the normally aspirated version but is the same block . I think if I remember correctly the valves are higher rated but the valve seats may be the same for parts count reasons . Any CEL codes that would put the ECU in limp mode ?

 

I'd recommend trying the X300 section

We habe the same basic styling, but the X308 is a totally different car

 

The temp. gauge is a glorified idiot light. It won't move off center until the 225 F or higher, at which time the engine may be done in.

The radiator was making noise? I don't understand.

257 psi does not make sense, I think you compression gauge is faulty.

 

The problem with the compression gauge being faulty is that i used two different compression gauges, and had the same reading. Is there anyway that say the head was bleeding compression from one head to another all the way across. Is there anyway possible the head could be warped, causing the cylinders to bleed into each other?

I just want to understand. The radiator was making a rumbling noise. Like i said, it was gauge, not a light and it sits in the dead-center. Something was going on and what would you suggest i do? I also have a camera that i could actually go down into the cylinders and look at the bars and valves, which i haven't done as of yet. Is there any way a stretched timing chain will cause the compression to be higher?

I did look up compression ratios on this particular engine and it said there were several six cylinder engines with that kind of compression, but i've never done a compression on an engine with over 100k miles and have 257 psi of pressure. I don't really know what all has been done to this engine.

If it was your car, what would you do? I can't drive it around with the radiator pressurizing! I always thought when it pressurizes: it means the cylinder was pumping compression into the radiator. Either via warped head, block, or head gasket. Even a cracked head could cause it! Is this right or wrong?

Please give me some advice because i've actually never worked on a Jag before. I have been a line mechanic at a local Ford dealer and most of the time and if we thought it was bad, we would just put a brick on the accelerator until it blew up if it was under warranty. If it wasn't, we would just order a new block, head, whatever. But, i'm at a loss with this Jag! I kind of feel like i should pull the head and put a new timing chain on it and have the valves checked to see if they need to be regrounded and have the head resurfaced and check the block to see how straight it is and the block deck.

Any help on what to do next would be gratefully appreciated because i know how expensive parts are for a Jag. However, i can get another used engine and guarantee for a year for under a grand. I would really like to see what's wrong with this Jag, but i don't know where to go next. Do i pull the head or what would you do?

Thanks so much for your help!

- Superdave

 

So, what you're saying is i can't put a turbo unit on this block because it would make it go into limp mode? I really liked your answer; can you give me some kind of answer as to what sort of compression this engine is supposed to have? The radiator is pressurizing and making a lot of noise. As soon as it is started up, within five minutes, i don't think the thermostat has enough time to open. I feel like that it's a headgasket or head problem,

I did a compression check with two different compression gauges and both said the same thing (257 psi) all the way down. I know that i've seen blown headgaskets that will leak into other cylinders. The head could be warped, causing this. But i've never worked on a Jag so i wouldn't know...

Can you please give me some advice on why you think the radiator is pressurizing? The engine itself runs very quietly. You can't even hear it run! There are also no codes stored on the computer. So, i'm at a loss.

But, the way the radiator is pressurizing: i'm afraid of blowing the engine up! What would you advise me to do next?

 

I have two compression gauges. Both say the same thing, but i haven't used them in decades due to retirement. But, if you think they're faulty: i'll buy a new gauge. They're really not that expensive. I really don't think they're faulty. The reason is i looked up the compression readings for some of these 6 cylinder blocks and some of them flat said that 257 psi was what it was supposed have. Others gave you some sort of equation (Cylinder v. size of piston and length of cylinder).

But that got WAY too complicated.

When i do a compression check, as long as each cylinder has over 100 psi and no more difference than 10%, then engine should run smoothly. If there is more than a 10% difference: then it's going to have a miss to it. What i'm really concerned about is the radiator pressurizing and my only thought is a cracked head or bad headgasket or even a warped head or block.

Thank you for your advice, however! If you have any more advice, please let me know, as i have never had this kind of opportunity to work on a Jaguar.

- Superdave

 

Still confused about my jag...

Radiator seems to be pressurizing and makes a lot of noise, like you would hear in a house with copper pipe but VERY loud. Does anyone know if this particular car is one you have to jack up the front end to burp it? In other words, to get the air out of the radiator. So far, i've done a compression check and it had 257 lbs. Did another compression check with a different compression gauge.

This compression check was done while the engine was cold, and it was the same. Every cylinder was 257 lbs. I was kind of hoping that one of the cylinders would be low, would explain the radiator pressurizing but the only thing i know to do is to pull the head and take it to a machine shop and have the head resurfaced and check the deck and make sure that it's square.

If anyone else has any other ideas, please let me. Also, this car is very underpowered. Is this normal for this particular car? I know it weighs 3,000 lbs which is kind of heavy for a 6 cylinder, but i just bought the car and was expecting it to have a lot more power. But this engine does not have a turbo.

Maybe that's all she can do? I don't know...

If anyone knows what would cause the radiator to pressurize like it has, i appreciate any help. I really think it is a head or head gasket, but i don't want to tear into if not.

 

The normally aspirated X300 is by no means underpowered. So far your description is a car that is underpowered but makes a noise at the front of the engine. Maybe you should not assume it is the radiator. What is the noise that it is making? A hiss, knocking? Is it constant or intermittent?

 

Hi superdave,

I have merged your thread from the X308 forum and your other thread in this forum so all your information is in this thread. Please don't start any new threads related to this subject. It becomes too confusing for other members to keep track of all that has been discussed.

Regarding your 1995 XJ6, when performing properly the AJ16 engine produces around 245 hp. That won't make the 4,000 pound vehicle a drag racer, but it's plenty of power to move it with grace and pace.

Regarding the compression tests, yes, it is very unusual to have the same reading for all cylinders, and for that reading to be so high. Forgive me for asking, but are you zeroing the gauge in between each cylinder test? Are you certain you are reading the psi scale and not another scale such as KPa?

Aside from the noise, what causes you to conclude the "radiator is pressurized?" Have you tested the pressure in the cooling system? One thought that occurs to me is that low power steering fluid can cause a groaning noise like pipes in an old building.

With a test fluid you can check for exhaust fumes in the coolant. Is there any white smoke in the exhaust that would indicate coolant is leaking into the combustion chambers?

If there is no sign of a blown head gasket, perhaps it just needs a good tuneup. For your Jaguar, a good tuneup includes the correct Champion spark plugs properly gapped, air filter, fuel filter, cleaning the ground points (especially those associated with the engine management system), cleaning the battery power connections, checking for cracks or leaks in the air intake plumbing, vacuum hoses and crankcase breather hoses, adding a good fuel injector cleaner to a full tank of gasoline, etc.

Another possibility is that a problem with the transmission or its electronic control circuits is causing the transmission to remain locked in one gear, such as 3rd. Is any kind of warning lamp illuminated on the instrument cluster? Have you checked the transmission fluid level?

Also, please visit the https://www.jaguarforums.com/forum/n...-intro-must-5/ and post a required introduction so we can learn something about you and give you a proper welcome.

Cheers,

Don

 

The noise from the radiator i heard was determined by i heard the noise and heard other radiator pressurize and how they sound. Hearing it so much that they'll actually blow apart! Also, i put my hand to radiator and the noise was making the radiator vibrate to pitch of the noise, which was VERY loud. I bought the car and took it for a test run. I only drove it for about 10 miles and had no problems except for the lack of power. Maybe i had it in the wrong gear? I drove the car home after paying for it, which was approximately 3 miles then once i switched it off, i began hearing this awful noise so i raised the hood back up, making the noise even louder. I squeezed the top radiator hose. It was very firm and hard, so i wasn't about to fool with the radiator cap but did feel of the radiator.

I didn't feel like it was very hot, but the radiator was vibrating with noises coming out of it. That's why i say it was pressurizing. Maybe it is something else! Maybe i need to check into this further and check the water pump, but i know when water pumps go out: they usually drip water from them. There was no water coming from the car at all.

I decided to do a compression check and i cranked each cylinder over, watching the compression gauge during each stroke. It got to the highest point on about 8 strokes, and each cylinder reached 257 psi. I thought it was kind of higher for an older car so i went and got another compression gauge and got the same results. I did let all of the air out of it between cylinders. But, i've heard you should get all of the compression within three strokes. Maybe this is where i went wrong?

I let it turn over 6 to 8 times because the compression kept building and building till it reached the 257 mark. I've never seen an engine with the same amount of pressure in each cylinder. I haven't used these gauges in over 10 years. I'm going to go buy a new compression gauge and check the compression, then i'm gonna check it by an air tank and pump 100 lbs w/ the valves closed and do a leak-down test. Maybe this might be helpful, i don't know.

But, with such high compression, maybe i should use 150 lbs of compression with both valves closed. There shouldn't be anymore than 20% difference than either cylinder or is it 10%, i'm not positive. I'll go online and research this; it's been so long since i've last done this!

If you have any other ideas or suggestions, please let me know and is it possible that there is something wrong with the radiator itself? The next day, when the engine cooled, i took the radiator cap off. The radiator had plenty of anti-freeze and showed no signs of oil or anything else in it. So, i pulled the bottom hose of it and water just GUSHED out of it. This tells me i don't think the radiator is plugged. I put the bottom hose back on and did it again, and water continued to pour. If the radiator was plugged up, that much water wouldn't just pour from it! Maybe i'm wrong; i didn't check the water pump. Maybe the noise is coming from the water pump.

But, maybe i should take the radiator down and have it checked.

I'll check on this and let you guys know. I'll definitely get me a new compression gauge and i know that i zeroed the gauge because i watched it during each revolution to see how long it would take to build up to it's maximum. It's just a habit of mine to do that.

Also i did notice that someone changed out all of the hose clamps with new ones and didn't bother putting new hoses on them since some of them were swollen.

Thank you for your time and consideration! I'll get back after i check this, and thank you for the help you've given me so far. You're right: there are a lot of things i should check. Thanks for the reminder. I am an old man, and i doubt if you've ever seen or used what they call a 'sun machine', which is what they used to use for tune-ups. Now they use computers that plug up to the car and that's used to diagnose. Kinda hard for me to get my head around lol

Thanks for your help!

- Superdave

 

The noise that i heard was a loud, bubbling rumbling vibrating noise that happened after the vehicle was turned off. I felt of the radiator and it was vibrating with noise. I could actually hear the noise coming from the radiator! But, maybe you guy are right. There are some thing that i need to check out on the car. The water pump and all bearings that are located on the front of the engine. Since this happened, i bought new belts and hoses. I just haven't gotten around to fooling with it.

I've heard radiators pressurize before but when they do: it's a loud rumbling, roaring noise. Like i said, i put my hand on the radiator and could feel the radiator vibrating with the noise. I had a feeling that the pressure cap was going to blow, so i left it alone until the next day. I undid the radiator cap and looked at the water; it looked normal and the water was yellow in color like anti-freeze. No oil mixed or any other substance, then i took the bottom radiator hose off and water shot out of it. Then i put the bottom hose back on it and filled it back up with water and checked it again.

Water shot out extremely fast which tells me that i don't think the radiator is blocked, i think it has plenty of flow but maybe there is something wrong with the water pump. I didn't occur to me to check the water pump or any other bearings on the front of the engine. Before i put the new hoses on, i'll go ahead and replace the water pump with a new one.

Thank you for any advice and anything else you can tell me. What do you think about a leak-down cylinder test? I've never done this test, but i understand all i have to do is pump 100 lbs of air and make sure both valves are shut. If there's a leak, there should be bubbles coming from the radiator or i should hear a hissing noise coming from the intake manafold or the exhaust pipe. Is this correct?

- Superdave