After about 15 minutes of driving I could easily cook an egg on my bonnet. Is this normal for a 4.2 series 3? I recon I could fry bacon if I put it right on the cam covers.

I have done, new rad, new thermostat, all new hoses, all cooling sensors, and new coolant at the correct ratio. The temp gauge sits right where it should too.

Anyone else find this?

 

Is your hood/bonnet insulation blanket present and accounted for?

Cheers
DD

 

Nope! It has a bituminous stuff that has been sprayed on, I don't think that's much of a heat shield.

I'm assuming you are talking of one that is similar to new cars? That fabric sort of stuff that's pinned under the hood?

Also, Doug, I'd like to thank you for all the help you offer to everyone, you've helped me MANY times. My jag would not be on the road with out you! I'd buy you a box of beers if i could. I think a lot of people would.

 

The Series IIs and early Series IIIs had a spray-on type insulator--'bituminous' , yes.

Later Series IIIs has a fiberglass blanket pinned to the underside, as you say. I think it insulates better. But nowadays you can buy modern trim-to-fit under hood insulating material and/or your local Jag-specific suppliers might offer a pre-cut version. Years ago I bought a gorgeous pre-cut insulator from Coventry West in Georgia. It was a dense closed-cell foam, actually. It looked great and really worked ! I have to think other suppliers offer the same.

Thanks, and I'm glad to help. I wouldn't be here if I didn't. I enjoy the conversations

Cheers
DD

 

My car had the "blanket" type pad on the bonnet. It had detiorated badly. Looked like a moth eaten bear rug. I removed it. I've not missed it. The bonnet paint had a dullish area overt the left side. I attribute that to the exhaust manifold of it's former DOHC 4.2. Heat shield notwithstanding.


It might have served as sound insulation as well. I don't miss it a bit, and my bonnet's paint has not gotten any worse.


Partly because the present V8 is configured differently? Yes, I think so. Lower manifold location and split four to a side. More room above the engine enables better air flow. A DOHC takes up so much room
and leaves little space for air flow.


Bituminous 1 and, I thought my plan of using "bed liner' was original.
Another example of "nothing new under the sun"!!!


Still going to spray t some day, just for looks, the under bonnet paint doesn't respond to polish!!!


Carl

 

The catalytic convertor is a major contributor to the heat problem under the hood as it is tucked up high near the exhaust manifolds and radiates heat upwards never benefiting from "under the car" airflow. When I had my wretched 6 still in the car I installed a hollow out cat ,..it is now laying on the ground in my "Xj6 junk pile of parts" left over from when I did the V8 swap.

I think that the closed cell foam underhood pads with a silver coating would work best at keeping the radiant heat down. I have louvers which some like and some hate ( I happen to like them and they work) They are functional. Gradually I am sorting this old car out

 

Yeah, the cats do get hot. In Ca, BAR specifies that they be up tight
as in the original. A look at my Cadillac manual shows them up close to the manifold outlet.


But, when, the muffler guy and I conferred, we agreed, well back, away from the transmission. transmissions don't like heat. Got past the referee. Luck or else. Not a bad guy, just rassling with reg's.


ORTH, the Cat on my Jeep is a way back. Had to replace it early on to get past SMOG. Was bolted in, now welded. Same guy that did the Jag.


Bituminous, a scientific name for tar.....


Carl

 

Harry,


I have a '77 XJ12L with a BBC. Hood is always cool or only warm to touch. Lizard Skin Ceramic Insulation cured my heat issues.


Spray-On Insulation - Automotive Insulation Coatings | LizardSkin


The "bituminous" separates from the metal, holds moisture, and rusts the bonnet from the inside out.


My prep included: 1)air craft stripper, covered with saran for an hour, removes easily with a plastic body putty applicator; 2) sanding; 3)Eastwood Rust Convertor; 4)Eastwood Rust Encapsulator; 5)Lizard Skin Ceramic Insulation.


For the purist, then you could add the factory style blanket insulation.

 

Thanks for the write up and photos! I'll certainly look in to this, very useful for future readers too.

At a minimum I'll put a new hear shield on the bonnet. Although the water trapped underneath sounds like something to certainly look into.

I also want to cook some breakfast on the hood before u fix it though :P I don't think many people have done THAT on a jag before. Too bad care about my paint so much

I almost want to

 

Many owners worry about excessive underhood temps, believing that this may have a negative effect on engine and accessory life.It seems that insulating the hood would tend to trap heat.

What's the concern with having a hot hood?

 

My only concern...perhaps unfounded?.... is that the heat will hurt the paint.

Cheers
DD

 

That was my thinking too!

I'm thinking Nix was painted with Real Automotive paint, perhaps still easily available in 1986, and any repair now would be that water based garbage, and I don't think I'd want to chance heat damage to it.

I've bought the blanket thing, but my car lacks the hangers inside the hood, so I'm looking at Clyde's post with Great interest!
(';')

 

Well I could burn my hand on it, which just seems wrong, other then that not too much, I guess the paint too but I'd protect the engine before the paint.

So no one else's hood get this hot it would seem?

 

Have you checked your engine temperature with a different source...
ie: an IR gun..(infrared)...just to be sure it's not running too hot.

 

Yup, with an IR fun, lower rad pipe sits around 80 degrees centigrade. Maybe the head is not getting proper coolant flow.

Water pump is new (remanufactured) too.

I'll do the temp test again. Once I get my hood open haha, it got stuck closed the other day.

 

How about the upper rad hose?

Measuring engine components will give useless data unless you know what temp for them is normal. Don't expect them to be at or near coolant temp.

 

Sorry I meant to say lower rad hose. The upper house sits at about 80 degrees centigrade too.

According to Dougs common repair list over on jag-lovers the "normal" operating temperature for these is about 80 to 90. I assume centigrade. Those numbers are from memory but close to what he had on there.

Added info: This one does have emissions control so no Cats.

 

I am with Doug. the elongated patch of less shiny Grosvenor
Brown on the bonnet of my 83 is over the left side, roughly
where the DOHC's exhaust manifold was. I attribute that to high
exhaust temps.


Elinor: as your car is a lump, as is mine, not only is the engine bay less crowded, but the exhaust temps are split and lower in the bay.
Less likely to damage NIX's gorgeous black.


Why would water based paint be not as good as the older solvent based paint. It is what is deposited and left after the solvent or water evaporates that matters.

I suspect there are some 'contact" glues that will attach the pad to the underside of the bonnet.


All:


Next time, I go on an extended Jaguar run, I'm gong to take the bonnet temp outside, with my palm and with my dandy little HF
sourced IFR. My interest is peaked. Why, I dunno???


And, to my way of thinking, it isn't coolant temp that matters as to bonnet temp, but ambient under bonnet temps, a combionatin of heat from the radiator and the alloy and iron of the engine, itself + exhaust, of course. But, exhaust is a major part of under hodd temp.


Water, As to the "tar" insulation. Not much in the engine cavity.
And, yes, when used under the car as under coating, once quite popular, it could trap water and make rust issues even worse, rather than protecting the steel.


Nice discussion, folks.


Carl

 

A couple of years ago JF had a couple of giveaways sponsored by
a vendor of hood liners. He passed away shortly after the last
giveaway.

But, they were well liked. He mentioned that they were cut from
aircraft firewall blanket material. It could probably be bought
from aircraftspruce.com

Make sure you ask for the free catalog, it is packed with goodies
that are hard to find anywhere else. No less than four choices
of english wheels, locking wire pliers in countless variations.

Everyone except LnrB of course. If hubby gets hold of that catalog,
it'll bankrupt the household.

 

Hmm. I hadn't considered that, Carl!

Now that I think about it, not only are they split, but they're Much Lower in the engine bay, and partly hidden below the valve covers.
Because the very best pigments are not necessarily water soluble. I'm sure the best blacks isn't! I'm loathe to have any of the 6 layers of clear coat start separating.
I learned last fall that my engine runs about 206F at the back of the head (the only place I could reach bare engine) and 213F on the thermostat housing. That was a 90F degree day, in traffic, with AC. I didn't think those were unreasonable numbers.
Waddaya mean "if hubby gets hold of it"??! I learned to walk in the tool crib!
My dad was a complete sucker for any new tool (gadget) to hit the market! He would have looked long and hard at that laser rust remover over in Off Topic.

I mentioned this catalog to husband just for fun, and he said some aircraft catalog or other is where he got the clecos I used to hold the floor together for welding! (The link below is to that specific post, not the whole thread.)
https://www.jaguarforums.com/forum/x...2/#post1102220

There's simply no surprising that man!
(';')